CN112088487B

CN112088487B - Motor system and turbo compressor including the same

Info

Publication number: CN112088487B
Application number: CN201980030695.9A
Authority: CN
Inventors: 小野贵晃; 入野裕介; 中泽勇二
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2018-05-08
Filing date: 2019-04-05
Publication date: 2022-01-07
Anticipated expiration: 2039-04-05
Also published as: CN112088487A; WO2019216080A1

Abstract

The invention provides an electric motor system and a turbo compressor including the same. The motor system (30) includes: a bearingless motor (40, 50); power supply units (61, 62) for applying voltages to armature windings (46a to 46c, 56a to 56c) and support windings (47a to 47c, 57a to 57c) provided on stators (44, 54) of bearingless motors (40, 50), respectively; and a control unit (60) that controls the power supply units (61, 62) such that one of an armature voltage VA that IS a voltage applied to the armature windings (46 a-46 c, 56 a-56 c) and a support current IS that IS a current flowing through the support windings (47 a-47 c, 57 a-57 c) IS increased and the other IS decreased. As a result, the bearingless motor can be operated in accordance with a predetermined power source capacity.

Description

Motor system and turbo compressor including the same

Technical Field

The invention relates to an electric motor system and a turbo compressor including the same.

Background

Conventionally, there is known a bearingless motor having a motor function of driving a rotor to rotate and a magnetic bearing function of controlling a radial position of the rotor (for example, patent document 1). In the bearingless motor of this document, it is possible to efficiently generate a supporting force for magnetically supporting the rotor while maintaining the magnetic linearity.

Patent document 1: japanese laid-open patent publication No. 2004-336968

Disclosure of Invention

Technical problems to be solved by the invention

When a bearingless motor is operated, a power supply for supplying electric power to the bearingless motor needs to be provided. Such power supplies have limited power supply capacities, and have limited currents and voltages that can be output. However, few attempts have been made to operate bearingless motors in conjunction with the limited power supply capacity described above.

The purpose of the invention is that: a bearingless motor is operated in accordance with a predetermined power source capacity.

Technical solution for solving technical problem

The first aspect of the present invention is directed to a motor system 30. The motor system 30 includes: a drive shaft 31 that drives the load 21 to rotate;

bearingless motors

40 and 50 each having

rotors

41 and 51 and

stators

44 and 54 provided with armature windings 46a to 46c and 56a to 56c and support windings 47a to 47c and 57a to 57c, respectively, and configured to rotationally drive the drive shaft 31 and contactlessly support a radial load of the drive shaft 31;

power supply units

61 and 62 for applying voltages to the armature windings 46a to 46c and 56a to 56c and the support windings 47a to 47c and 57a to 57c, respectively; and a control unit 60 that controls the

power supply units

61 and 62 such that one of an armature voltage VA applied to the armature windings 46a to 46c and 56a to 56c and a support current IS flowing through the support windings 47a to 47c and 57a to 57c IS increased and the other IS decreased.

In the first aspect, by increasing one of the armature voltage VA and the support current IS and decreasing the other of the armature voltage VA and the support current IS, the armature voltage VA and the support current IS can be adjusted within the range of the power supply capacity of the

power supply units

61 and 62 in accordance with the operating conditions of various devices in which the motor system 30 IS used.

A second aspect of the present invention IS the power supply device according to the first aspect, wherein the control unit 60 controls the

power supply units

61 and 62 such that the armature voltage VA increases and the support current IS decreases, or such that the support current IS increases and the armature voltage VA decreases.

In the second aspect of the present invention, the support current IS or the armature voltage VA can be reduced while maintaining the radial support force.

A third aspect of the present invention IS the first or second aspect, wherein the control unit 60 controls the

power supply units

61 and 62 such that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value.

In the third aspect, the support current IS can be made not to exceed the first upper limit value, and the radial support force due to the armature current IA, which IS the current flowing through the armature windings 46a to 46c and 56a to 56c, can be increased. This IS particularly effective when the radial supporting force IS increased in a state where the supporting current IS reaches the first upper limit value or a value in the vicinity thereof.

A fourth aspect of the present invention IS directed to any one of the first to third aspects, wherein the control unit 60 controls the

power supply units

61 and 62 such that the support current IS increases and the armature voltage VA does not exceed a predetermined second upper limit value.

In the fourth aspect, the armature voltage VA can be prevented from exceeding the second upper limit value, but when the rotation speed of the

bearingless motors

40 and 50 is increased, for example, the radial supporting force by the armature current IA may be decreased. In contrast, by increasing the support current IS, the radial support force by the support current IS can compensate for the drop.

A fifth aspect of the present invention IS directed to any one of the first to fourth aspects, wherein the control unit 60 controls the

power supply units

61 and 62 such that the armature voltage VA decreases and the support current IS increases, or such that the support current IS decreases and the armature voltage VA increases.

In the fifth aspect of the present invention, the support current IS or the armature voltage VA can be increased while maintaining the radial support force.

A sixth aspect of the present invention IS directed to any one of the first to fifth aspects, wherein the control unit 60 controls the

power supply units

61 and 62 such that the armature voltage VA decreases and the support current IS exceeds a predetermined first lower limit value.

In the sixth aspect, the support current IS can be made to exceed the first lower limit value. This enables heat generation in the support windings 47a to 47c and 57a to 57c to be utilized as needed, for example.

A seventh aspect of the present invention IS directed to any one of the first to sixth aspects, wherein the control unit 60 controls the

power supply units

61 and 62 such that the support current IS decreases and the armature voltage VA exceeds a predetermined second lower limit value.

In the seventh aspect, the armature voltage VA can be made to exceed the second lower limit value. This enables, for example, heat generation in the armature windings 46a to 46c and 56a to 56c to be utilized as needed.

An eighth aspect of the present invention is directed to the turbo compressor 12. The turbo compressor 12 includes: the motor system 30 according to any one of the first to seventh aspects; and an impeller 21 connected to the drive shaft 31 of the motor system 30 as the load 21.

In the eighth aspect, in the turbo compressor 12, the impeller 21 is driven to rotate by the

bearingless motors

40 and 50.

A ninth aspect of the present invention IS the refrigeration system according to the sixth aspect, wherein the turbo compressor 12 IS provided in a refrigerant circuit 11 that performs a refrigeration cycle, and IS configured to compress a refrigerant by the impeller 21, and when the turbo compressor 12 IS operated in a region C or a surge region D where rotating stall occurs, the control unit 60 controls the

power supply units

61 and 62 so that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value.

In the ninth aspect, when the turbo compressor 12 is operated in the region C or the surge region D where the rotating stall occurs, that is, when the load torque of the

bearingless motors

40 and 50 is small and the required radial support force is large, the radial support force by the armature current IA can be increased. Therefore, even if the support current IS kept to be equal to or less than the first upper limit value, the radial support force of the

bearingless motors

40 and 50 can be increased by increasing the armature current IA.

Drawings

Fig. 1 is a schematic diagram illustrating a configuration of an air conditioner according to an embodiment;

fig. 2 is a longitudinal sectional view illustrating a structure of a turbo compressor;

fig. 3 is a transverse sectional view illustrating the structure of a bearingless motor;

fig. 4 is a diagram for explaining an operation region of the turbo compressor.

Detailed Description

(air-conditioning apparatus)

Fig. 1 illustrates a configuration of an air conditioner 10 according to an embodiment. The air conditioner 10 includes a refrigerant circuit 11. The refrigerant circuit 11 includes a turbo compressor 12, a condenser 13, an expansion valve 14, and an evaporator 15, and is configured to circulate a refrigerant to perform a refrigeration cycle. For example, the condenser 13 and the evaporator 15 are constituted by a transverse fin-type heat exchanger, and the expansion valve 14 is constituted by an electric valve.

(turbo compressor)

Fig. 2 illustrates the structure of the turbo compressor 12 shown in fig. 1. The turbo compressor 12 is provided in the refrigerant circuit 11 and configured to compress a refrigerant by an impeller 21 described later. In this example, the turbocompressor 12 comprises a housing 20, an impeller 21 and a motor system 30. The motor system 30 includes a drive shaft 31, a first bearingless motor 40, a second bearingless motor 50, a control unit 60, a first power supply unit 61, and a second power supply unit 62. In this example, the motor system 30 further includes a first bottoming bearing 71 and a second bottoming bearing 72, and a thrust magnetic bearing 73.

In the following description, the "axial direction" is a rotation axis direction and a direction of the axial center of the drive shaft 31, and the "radial direction" is a direction orthogonal to the axial direction of the drive shaft 31. The "outer peripheral side" is a side away from the axial center of the drive shaft 31, and the "inner peripheral side" is a side closer to the axial center of the drive shaft 31.

[ casing ]

The housing 20 is formed in a cylindrical shape with both ends closed, and is disposed such that the cylindrical axis direction is the horizontal direction. The space in the housing 20 is partitioned by the wall portion 20a, and the space on the right side of the wall portion 20a constitutes an impeller chamber S1 in which the impeller 21 is housed, and the space on the left side of the wall portion 20a constitutes a motor chamber S2 in which the first bearingless motor 40 and the second bearingless motor 50 are housed. The motor chamber S2 accommodates the first bearingless motor 40 and the second bearingless motor 50, the first bottoming bearing 71 and the second bottoming bearing 72, and the thrust magnetic bearing 73, which are fixed to the inner peripheral wall of the motor chamber S2.

[ Driving shaft ]

The drive shaft 31 is provided to rotationally drive the load 21 (the impeller 21 in this example). In this example, the drive shaft 31 extends in the axial direction within the housing 20 and couples the impeller 21 to the first bearingless motor 40 and the second bearingless motor 50. Specifically, the impeller 21 is fixed to one end portion of the drive shaft 31; the first bearingless motor 40 and the second bearingless motor 50 are disposed at a middle portion of the drive shaft 31. A disk-shaped portion (hereinafter also referred to as a disk portion 31a) is provided at the other end portion of the drive shaft 31 (i.e., the end portion of the drive shaft 31 on the opposite side from the one end portion to which the impeller 21 is fixed). The disk portion 31a is made of a magnetic material (e.g., iron).

[ impeller (load) ])

The impeller 21 is formed of a plurality of blades having a substantially conical outer shape and is accommodated in the impeller chamber S1 in a state of being fixed to one end portion of the drive shaft 31. The suction pipe P1 and the discharge pipe P2 are connected to the impeller chamber S1. The suction pipe P1 is provided to guide the refrigerant (fluid) from the outside to the impeller chamber S1. The discharge pipe P2 is provided to return the high-pressure refrigerant (fluid) compressed in the impeller chamber S1 to the outside. That is, in this example, the impeller 21 and the impeller chamber S1 constitute a compression mechanism.

[ Bearingless Motor ]

The first bearingless motor 40 and the second bearingless motor 50 have the same structure as each other. Therefore, here, only the structure of the first bearingless motor 40 will be described.

The first bearingless motor 40 has one stator 44 and a pair of rotors 41, and is configured to rotationally drive the drive shaft 31 and contactlessly support a radial load of the drive shaft 31. The rotor 41 is fixed to the drive shaft 31, and the stator 44 is fixed to the inner peripheral wall of the housing 20.

As shown in fig. 3, in this example, the first bearingless motor 40 is a commutating pole (continuous pole) type bearingless motor.

The rotor 41 of the first bearingless motor 40 includes a rotor core 42 and a plurality of (four in this example) permanent magnets 43 embedded in the rotor core 42. The rotor core 42 is made of a magnetic material (e.g., laminated steel plate) and is formed in a cylindrical shape. A shaft hole through which the drive shaft 31 passes is formed in the center of the rotor core 42.

The plurality of permanent magnets 43 are spaced apart from each other at a predetermined angular interval (in this example, an angular interval of 90 °) in the circumferential direction of the rotor 41. The outer peripheral surface side of the four permanent magnets 43 becomes an N-pole, and a portion of the outer peripheral surface of the rotor core 42 located between the four permanent magnets 43 in the circumferential direction of the rotor 41 functions as an S-pole and is a pseudo S-pole. The outer peripheral surfaces of the four permanent magnets 43 may be S-poles.

The stator 44 of the first bearingless motor 40 is made of a magnetic material (for example, laminated steel plate), and includes a back yoke 45, a plurality of teeth (not shown), and armature windings 46a to 46c and support windings 47a to 47c wound around the teeth. The back yoke portion 45 is formed in a cylindrical shape. The armature windings 46a to 46c and the support windings 47a to 47c are wound around the respective teeth in a distributed winding manner. The armature windings 46a to 46c and the support windings 47a to 47c may be wound around the respective teeth in a concentrated winding manner.

The armature windings 46a to 46c are windings wound around the inner peripheral portions of the teeth. The armature windings 46a to 46c are formed of a U-phase armature winding 46a surrounded by a thick solid line in fig. 3, a V-phase armature winding 46b surrounded by a thick broken line in fig. 3, and a W-phase armature winding 46c surrounded by a thin solid line in fig. 3.

The support windings 47a to 47c are windings wound around the outer peripheral portions of the teeth. The support windings 47a to 47c are constituted by a U-phase support winding 47a surrounded by a thick solid line in fig. 3, a V-phase support winding 47b surrounded by a thick broken line in fig. 3, and a W-phase support winding 47c surrounded by a thin solid line in fig. 3.

[ touchdown bearing ]

The first bottoming bearing 71 is disposed near one end portion (right end portion in fig. 2) of the drive shaft 31, and the second bottoming bearing 72 is disposed near the other end portion of the drive shaft 31. The first bottoming bearing 71 and the second bottoming bearing 72 are configured to support the drive shaft 31 when the first bearingless motor 40 and the second bearingless motor 50 are not energized (i.e., when the drive shaft 31 is not floating).

[ thrust magnetic bearing ]

The thrust magnet bearing 73 includes a first thrust electromagnet 74a and a second thrust electromagnet 74b, and is configured to support the disk portion 31a of the drive shaft 31 in a noncontact manner by an electromagnetic force. Specifically, the first thrust electromagnet 74a and the second thrust electromagnet 74b are each formed in an annular shape, face each other across the disk portion 31a of the drive shaft 31, and support the disk portion 31a of the drive shaft 31 in a non-contact manner by the combined electromagnetic force of the first thrust electromagnet 74a and the second thrust electromagnet 74 b.

[ various sensors ]

Various sensors (not shown) such as a position sensor, a current sensor, and a rotational speed sensor are provided in each part of the motor system 30. For example, the first bearingless motor 40 and the second bearingless motor 50 are provided with position sensors (not shown) that output detection signals corresponding to the radial (radial) positions of the

rotors

41 and 51, and the thrust magnetic bearing 73 is provided with a position sensor (not shown) that outputs a detection signal corresponding to the position of the drive shaft 31 in the thrust direction (axial). These position sensors are constituted by, for example, eddy current type displacement sensors that detect a gap (distance) with a measurement target.

[ control section ]

The control unit 60 is configured to generate and output the armature voltage command value, the support voltage command value, and the thrust voltage command value such that the rotation speed of the drive shaft 31 reaches a predetermined target rotation speed in a state where the drive shaft 31 is supported in a non-contact manner, based on detection signals from various sensors provided at various portions of the motor system 30 and information such as the target rotation speed of the drive shaft 31. The armature voltage command value is a command value for controlling the voltage supplied to the armature windings 46a to 46c, 56a to 56c of the first bearingless motor 40 and the second bearingless motor 50. The support voltage command value is a command value for controlling the voltage supplied to the support windings 47a to 47c, 57a to 57c of the first bearingless motor 40 and the second bearingless motor 50. The thrust voltage command value is a command value for controlling the voltage supplied to the windings (not shown) of the first thrust electromagnet 74a and the second thrust electromagnet 74b of the thrust magnetic bearing 73. The control unit 60 is configured by, for example, an arithmetic processing unit such as a CPU, a storage unit such as a memory for storing a program and information for operating the arithmetic processing unit, and the like.

[ Power supply section ]

The first power supply unit 61 is configured to supply voltage to the armature windings 46a to 46c, 56a to 56c of the first bearingless motor 40 and the second bearingless motor 50 based on the armature voltage command value output from the control unit 60. The second power supply unit 62 is configured to supply a voltage to the support windings 47a to 47c, 57a to 57c of the first bearingless motor 40 and the second bearingless motor 50 based on the support voltage command value output from the control unit 60. By controlling the voltages applied to the armature windings 46a to 46c, 56a to 56c, and the support windings 47a to 47c, and 57a to 57c of the first bearingless motor 40 and the second bearingless motor 50, the currents flowing through the windings 46a to 46c, 56a to 56c, 47a to 47c, and 57a to 57c) are controlled, and thereby the torque and the support force generated by the first bearingless motor 40 and the second bearingless motor 50 can be controlled. The first power supply unit 61 and the second power supply unit 62 are formed of, for example, pwm (pulse Width modulation) amplifiers. The first power supply section 61 and the second power supply section 62 constitute a power supply section.

(operation region of turbo compressor)

Fig. 4 is a diagram for explaining an operation region of the turbo compressor 12. In the figure, the horizontal axis represents the refrigerant fluid flow rate, and the vertical axis represents the compression work. The turbo compressor 12 can be operated in a predetermined operation region by being supplied with electric power from the first power supply unit 61 and the second power supply unit 62.

The predetermined operating region mainly includes a steady operating region a inside the surge line, a high-load torque region B, a turbulent flow region C, and a surge region D outside the surge line, which are indicated by thick lines in fig. 4. In the present specification, the high load torque region B is also referred to as a "region requiring the maximum driving torque of the turbo compressor 12". In addition, the turbulent flow region C is also referred to as a "region where rotating stall occurs".

The steady operation region a is a region indicated by a symbol a in fig. 4, in which the load torque of the impeller 21 and the drive shaft 31 (i.e., the torque for driving the impeller 21 and the drive shaft 31 to rotate) is relatively small and the radial load of the drive shaft 31 is also relatively small.

The high load torque region B is a region indicated by symbol B in fig. 4, and in this high load torque region B, the load torque of the impeller 21 and the drive shaft 31 is relatively large and the radial load of the drive shaft 31 is also relatively large. The load torque of the impeller 21 and the drive shaft 31 in the turbo compressor 12 is maximum at the upper right-most point in fig. 4 in the high load torque region B. However, the radial load of the drive shaft 31 in the turbo compressor 12 is not maximized in the high load torque region B.

The turbulent flow region C is a region indicated by symbol C in fig. 4, in which the load torque ratio of the impeller 21 and the drive shaft 31 is small and the radial load of the drive shaft 31 is large.

The surge region D is a region indicated by a reference symbol D in fig. 4, and the turbo compressor 12 may be temporarily operated in the surge region D in an emergency such as a power failure. In the surge region D, the load-torque ratio between the impeller 21 and the drive shaft 31 is small, and the radial load of the drive shaft 31 is large. The radial load of the drive shaft 31 in the turbocompressor 12 is greatest at a specified point in this surge region D.

(operation of control part and Power supply part)

The operation of the control unit 60, the first power supply unit 61, and the second power supply unit 62 will be described. The control unit 60 supplies voltages to the armature windings 46a to 46c and the support windings 47a to 47c of the first bearingless motor 40 and the armature windings 56a to 56c and the support windings 57a to 57c of the second bearingless motor 50 to generate the armature current IA and the support current IS so as to output a radial support force for supporting a radial load corresponding to the state of the turbo compressor 12.

Here, the radial support force IS the sum of the radial support force due to the support current IS and the radial support force due to both the armature current IA and the support current IS (also referred to as the radial support force due to the armature current IA in this specification). Regarding the radial support force caused by both the armature current IA and the support current IS, the radial support force increases when the d-axis component of the armature current IA (hereinafter, d-axis current) IS increased, and decreases when the d-axis current IS decreased; the radial support force increases when the absolute value of the q-axis component of the armature current IA (hereinafter, q-axis current) is increased, and decreases when the absolute value of the q-axis current is decreased.

For example, in the steady operation region a, the controller 60 controls the first power supply unit 61 (so-called maximum torque/current control) so that the armature windings 46a to 46c and 56a to 56c generate torque most efficiently with respect to the armature current IA, and controls the second power supply unit 62 so that radial support force corresponding to the state of the turbo compressor 12 is output to the support windings 47a to 47c and 57a to 57 c.

For example, in a region other than the steady operation region a, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that one of the armature voltage VA, which IS a voltage applied to the armature windings 46a to 46c of the first bearingless motor 40 and the armature windings 56a to 56c of the second bearingless motor 50, and the support current IS, which IS a current flowing through the support windings 47a to 47c, 57a to 57c, IS increased and the other IS decreased. Several examples of such control will be described below.

[ Strong magnetic flux control ]

The control unit 60 performs strong magnetic flux control of the armature windings 46a to 46C and 56a to 56C (that is, control of generating a positive D-axis current) at, for example, a turbulent region C and a surge region D in which the radial load is increased due to a small load torque ratio, at the end of operation of the turbo compressor 12, and at the start of the turbo compressor 12.

Here, the control unit 60 increases the armature voltage command value to the first power supply unit 61 to increase the armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50, and decreases the support voltage command value to the second power supply unit 62 to decrease the support current IS in the first bearingless motor 40 and the second bearingless motor 50. The control unit 60 also controls the first power supply unit 61 and the second power supply unit 62 so that the support current IS in the first bearingless motor 40 and the second bearingless motor 50 does not exceed a predetermined first upper limit value (for example, determined by the power supply capacity of the second power supply unit 62). This can increase the armature current IA, which IS a current flowing through the armature windings 46a to 46c and 56a to 56c, without increasing the support current IS, thereby increasing the radial support force. Therefore, the power supply capacity of the second power supply unit 62 can be set relatively small with respect to the maximum radial support force that can be generated by the first bearingless motor 40 and the second bearingless motor 50.

For example, when the temperature of the support windings 47a to 47c and 57a to 57c becomes equal to or higher than a predetermined reference value, the control unit 60 may perform the high magnetic flux control by the first power supply unit 61 and reduce the support current IS by the second power supply unit 62. This can reduce copper loss in the support windings 47a to 47c and 57a to 57c while maintaining the radial support force, thereby suppressing an excessive temperature rise in the support windings 47a to 47c and 57a to 57 c. As a result, the reliability of the turbo compressor 12 can be improved.

For example, when the rotation speeds of the first bearingless motor 40 and the second bearingless motor 50 are relatively small and the armature voltage VA IS relatively small, the control unit 60 may perform the high-flux control by the first power supply unit 61 and reduce the support current IS by the second power supply unit 62. This makes it possible to increase the armature voltage VA while maintaining the radial support force, and to improve controllability of the first bearingless motor 40 and the second bearingless motor 50 by improving the output accuracy of the armature voltage VA.

In addition, when oil IS present in the air gap between the rotor 41 and the stator 44 of the first bearingless motor 40 and between the rotor 51 and the stator 54 of the second bearingless motor 50, the control unit 60 may perform the high-flux control by the first power supply unit 61 and reduce the support current IS by the second power supply unit 62. This can increase the copper loss and the iron loss in the armature windings 46a to 46c and 56a to 56c, and heat the oil in the air gap by the heat generation thereof, thereby reducing the viscosity of the oil. As a result, the rotation loss of the first bearingless motor 40 and the second bearingless motor 50 can be reduced.

In addition, when the air conditioner 10 performs the heating operation, the control unit 60 may perform the high-intensity magnetic flux control by the first power supply unit 61 and reduce the support current IS by the second power supply unit 62. This can increase the copper loss and the iron loss in the armature windings 46a to 46c and 56a to 56c, and heat the refrigerant existing in the motor chamber S2 by the heat generation. The heat accumulated in the refrigerant by this heating is released to the air in the target space in the condenser 13. Therefore, the heating performance of the air conditioner 10 can be improved.

In addition, when the demagnetization resisting forces of the permanent magnet 43 of the first bearingless motor 40 and the permanent magnet 53 of the second bearingless motor 50 are small, the control unit 60 may perform the high-flux control by the first power supply unit 61 and reduce the support current IS by the second power supply unit 62. The magnetic flux generated by the support current IS may cause demagnetization of the permanent magnets 43 and 53, but demagnetization IS less likely to occur by performing such control. Therefore, since the permanent magnets 43 and 53 having a small coercive force can be used, the degree of freedom in designing the first bearingless motor 40 and the second bearingless motor 50 can be increased while achieving cost reduction.

[ flux weakening control ]

For example, in the high-speed operation region, the control unit 60 performs flux weakening control (i.e., control for generating a negative d-axis current) of the armature windings 46a to 46c and 56a to 56 c. The high-speed operation region is a region in which the armature voltage VA is operated at a rotation speed exceeding a rotation speed that reaches a predetermined second upper limit value (determined by the power supply capacity of the first power supply unit 61, for example) without the weak magnetic flux control. In addition, the armature current IA increases when the field weakening control is performed, as compared with the case where the field weakening control is not performed.

Here, the control unit 60 increases the support voltage command value to the second power supply unit 62 to increase the support current IS in the first bearingless motor 40 and the second bearingless motor 50, and decreases the armature voltage command value to the first power supply unit 61 to decrease the armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50. The control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50 does not exceed the second upper limit value. Thus, the turbo compressor 12 can be operated in the high-speed operation region without increasing the armature voltage VA, and a decrease in the radial support force associated with the weak magnetic flux control can be compensated for by an increase in the support current IS. Therefore, the power supply capacity of the first power supply unit 61 can be set relatively small with respect to the width of the high speed operation region of the turbo compressor 12.

The control unit 60 may perform flux weakening control at the time of starting the turbo compressor 12, for example. When the turbo compressor 12 is started, the drive shaft 31 is supported by the first and second bottoming

bearings

71 and 72, and therefore, when a relatively large radial support force is required due to the magnetic force of the permanent magnets 43 and 53 of the first and second

bearingless motors

40 and 50, the flux weakening control seems to act to reduce the magnetic force of the permanent magnets 43 and 53, thereby reducing the required radial support force. Therefore, the controllability of the first bearingless motor 40 and the second bearingless motor 50 can be improved.

In addition, when oil IS present in the air gap between the rotor 41 and the stator 44 in the first bearingless motor 40 and the air gap between the rotor 51 and the stator 54 in the second bearingless motor 50, the control unit 60 may perform flux weakening control to increase the support current IS. This can increase the copper loss in the support windings 47a to 47c and 57a to 57c, and the oil in the air gap is heated by the heat generation thereof, thereby reducing the viscosity of the oil. As a result, the rotation loss of the first bearingless motor 40 and the second bearingless motor 50 can be reduced.

In addition, when the air conditioner 10 performs the heating operation, the control unit 60 may perform the flux weakening control and increase the support current IS. This can increase the copper loss in the support windings 47a to 47c and 57a to 57c, and heat the refrigerant existing in the motor chamber S2 by the heat generated thereby. The heat accumulated in the refrigerant by this heating is released to the air in the target space in the condenser 13. Therefore, the heating performance of the air conditioner 10 can be improved.

[ regenerative control ]

For example, when the operation in which the radial load becomes large is finished, the control unit 60 performs regenerative control (i.e., control for generating a negative q-axis current).

Here, the control unit 60 increases the armature voltage command value to the first power supply unit 61 to increase the armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50, and decreases the support voltage command value to the second power supply unit 62 to decrease the support current IS in the first bearingless motor 40 and the second bearingless motor 50. The control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the support current IS in the first bearingless motor 40 and the second bearingless motor 50 does not exceed the first upper limit value. This can increase the armature current IA without increasing the support current IS, thereby increasing the radial support force. Therefore, the power supply capacity of the second power supply unit 62 can be set relatively small with respect to the maximum radial support force that can be generated by the first bearingless motor 40 and the second bearingless motor 50. Further, by regenerating the rotational energy, energy saving of the turbo compressor 12 can be achieved, and the time for stopping the rotation can be shortened.

Further, when the radial load is rapidly increased in the case of controlling the first bearingless motor 40 and the second bearingless motor 50 while generating the positive q-axis current by the first power supply unit 61, the control unit 60 may perform regenerative control for generating a negative q-axis current having an absolute value larger than the positive q-axis current. Thus, the radial support force can be increased without increasing the support current IS by the second power supply unit 62. It is also conceivable that the absolute value of the positive q-axis current is increased without reversing the polarity, and the same effect can be obtained.

Effects of the embodiment

The motor system 30 of the present embodiment includes: a drive shaft 31 for driving the load bearing 21 to rotate; a first bearingless motor 40 and a second bearingless motor 50 each having

rotors

41 and 51 and

stators

44 and 54 provided with armature windings 46a to 46c and 56a to 56c and support windings 47a to 47c and 57a to 57c, respectively, for rotatably driving the drive shaft 31 and contactlessly supporting a radial load of the drive shaft 31; a first power supply unit 61 for applying a voltage to the armature windings 46a to 46c and 56a to 56 c; a second power supply unit 62 for applying a voltage to the support windings 47a to 47c and 57a to 57 c; and a control unit 60 that controls the first power supply unit 61 and the second power supply unit 62 such that one of an armature voltage VA applied to the armature windings 46a to 46c and 56a to 56c and a support current IS flowing through the support windings 47a to 47c and 57a to 57c IS increased and the other IS decreased.

Therefore, by increasing one of the armature voltage VA and the support current IS and decreasing the other, the armature voltage VA and the support current IS can be adjusted within the range of the power supply capacity of each of the first power supply unit 61 and the second power supply unit 62 in accordance with the operating conditions of various devices using the motor system 30. That is, when the power supply capacities of the first power supply unit 61 and the second power supply unit 62 are limited, if the power supply capacity of one of the

power supply units

61 and 62 is insufficient to obtain a desired output in the first bearingless motor 40 and the second bearingless motor 50, the shortage can be compensated by the other

power supply unit

61 or 62.

In the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the armature voltage VA increases and the support current IS decreases, or such that the support current IS increases and the armature voltage VA decreases. When such control is adopted, the operating region of the motor system 30 can be widened.

In the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value. Therefore, the support current IS can be made not to exceed the first upper limit value, and the radial support force due to the armature current IA, which IS the current flowing through the armature windings 46a to 46c and 56a to 56c, can be increased. This corresponds to, for example, the case where the first power supply unit 61 performs the high magnetic flux control. This IS particularly effective when the radial supporting force IS increased in a state where the supporting current IS reaches the first upper limit value or a value in the vicinity thereof.

In the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the support current IS increases and the armature voltage VA does not exceed a predetermined second upper limit value. Therefore, the armature voltage VA can not exceed the second upper limit value, but when the rotation speed of the first bearingless motor 40 and the second bearingless motor 50 is increased, for example, the radial support force by the armature current IA may be decreased. This corresponds to the case where the first power supply unit 61 performs the weak magnetic flux control, for example. In contrast, the support current IS can be increased by the second power supply unit 62, and the radial support force due to the support current IS can be used to compensate for the drop.

In the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the armature voltage VA decreases and the support current IS increases, or such that the support current IS decreases and the armature voltage VA increases. When such control is adopted, for example, heat generation in the armature windings 46a to 46c, 56a to 56c or the support windings 47a to 47c, 57a to 57c can be utilized as necessary.

In the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the armature voltage VA decreases and the support current IS exceeds a predetermined first lower limit value. Therefore, the support current IS can exceed the first lower limit value. Accordingly, for example, heat generation in the support windings 47a to 47c and 57a to 57c can be utilized as needed, or the controllability of the first bearingless motor 40 and the second bearingless motor 50 can be improved by improving the detection accuracy of the support current IS.

In the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the support current IS decreases and the armature voltage VA exceeds a predetermined second lower limit value. Therefore, the armature voltage VA can exceed the second lower limit value. Accordingly, for example, the controllability of the first bearingless motor 40 and the second bearingless motor 50 can be improved by utilizing heat generation in the armature windings 46a to 46c and 56a to 56c or by improving the output accuracy of the armature voltage VA as needed.

Further, the turbo compressor 12 of the present embodiment includes: the motor system 30 of the present embodiment; and an impeller 21 connected to the drive shaft 31 of the motor system 30 and serving as the load 21. Therefore, in the turbo compressor 12, the impeller 21 is driven to rotate by the first bearingless motor 40 and the second bearingless motor 50.

The turbo compressor 12 of the present embodiment IS provided in a refrigerant circuit 11 that performs a refrigeration cycle, and IS configured such that the impeller 21 compresses a refrigerant, and when the turbo compressor 12 IS operated in a region C or a surge region D where rotating stall occurs, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value. Therefore, when the load torque of the first bearingless motor 40 and the second bearingless motor 50 is small and the required radial support force is large, the radial support force by the armature current IA can be increased. Therefore, even if the support current IS kept to be equal to or lower than the first upper limit value, the radial support force of the first bearingless motor 40 and the second bearingless motor 50 can be increased by increasing the armature current IA.

(other embodiments)

The above embodiment may have the following configuration.

For example, the motor system 30 may have only one bearingless motor, or three or more bearingless motors. Here, in the former case, the motor system 30 preferably has a radial magnetic bearing.

The types of the first bearingless motor 40 and the second bearingless motor 50 are not limited to the commutating pole type, and may be, for example, a Surface Magnet type (SPM) in which a Permanent Magnet is bonded to the Surface of a rotor, an Interior Magnet type (IPM) in which a Permanent Magnet is embedded in the rotor, an insertion type, a bpm (built Permanent Magnet) type, or a positive salient pole type. The types of the two

bearingless motors

40 and 50 may be different from each other. Each of the

bearingless motors

40 and 50 may be any of a bearingless motor in which the d-axis self-inductance and the q-axis self-inductance of the armature are substantially equal and have no saliency, a bearingless motor in which the d-axis self-inductance of the armature is smaller than the q-axis self-inductance and has reverse saliency, and a bearingless motor in which the d-axis self-inductance of the armature is larger than the q-axis self-inductance and has positive saliency. Here, as the bearingless motor having no saliency, a commutating pole type, a surface magnet type, and the like can be cited; examples of the bearingless motor having the reverse salient polarity include an embedded magnet type, an insertion type, a BPM type, and the like; the bearingless motor having positive saliency may be a positive saliency type motor.

The number of impellers 21 included in the turbo compressor 12 may be two or more, and for example, one impeller 21 may be attached to each of both ends of the drive shaft 31.

The control method of the first power supply unit 61 in the steady operation region a may be a method other than the maximum torque/current control, and may be, for example, a maximum efficiency control (a control for minimizing the loss) or a control for setting the power factor to 1 (a control for setting the power factor to substantially 1).

It should be noted that the use of the motor system 30 is not limited to the turbo compressor 12, of course.

The embodiments and modifications have been described above, but it is understood that various changes and modifications can be made without departing from the spirit and scope of the claims. The above embodiments and modifications may be appropriately combined or substituted as long as the functions of the objects of the present invention are not affected.

Industrial applicability-

As described above, the present invention is useful for a motor system and a turbo compressor including the motor system.

-description of symbols-

11 refrigerant circuit

12 turbo compressor

21 impeller (load)

30 electric motor system

31 drive shaft

40 first bearingless motor (bearingless motor)

41 rotor

46 a-46 c armature winding

47 a-47 c support winding

50 second bearingless motor (bearingless motor)

51 rotor

56 a-56 c armature winding

57 a-57 c support winding

60 control part

61 first power supply part (power supply part)

62 second power supply part (Power supply part)

Claims

1. An electric motor system, comprising:

a drive shaft (31) that rotationally drives the load (21);

a bearingless motor (40, 50) having a rotor (41, 51) and a stator (44, 54) provided with armature windings (46a to 46c, 56a to 56c) and support windings (47a to 47c, 57a to 57c), and configured to rotationally drive the drive shaft (31) and contactlessly support a radial load of the drive shaft (31);

power supply units (61, 62) for applying voltages to the armature windings (46a to 46c, 56a to 56c) and the support windings (47a to 47c, 57a to 57 c); and

and a control unit (60) that controls the power supply units (61, 62) so as to output a radial support force that IS the sum of a radial support force generated by a support current IS, which IS a current flowing through the support windings (47a to 47c, 57a to 57c), and a radial support force generated by both an armature current IA, which IS a current flowing through the armature windings (46a to 46c, 56a to 56c), and the support current IS, and so as to increase one of an armature voltage VA, which IS a voltage applied to the armature windings (46a to 46c, 56a to 56c), and the support current IS, and decrease the other.

2. The motor system of claim 1,

the control unit (60) controls the power supply units (61, 62) such that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value.

3. The motor system of claim 1,

the control unit (60) controls the power supply units (61, 62) such that the support current IS increases and the armature voltage VA does not exceed a predetermined second upper limit value.

4. The motor system of claim 1,

the control unit (60) controls the power supply units (61, 62) such that the armature voltage VA decreases and the support current IS exceeds a predetermined first lower limit value.

5. The motor system of claim 1,

the control unit (60) controls the power supply units (61, 62) such that the support current IS decreases and the armature voltage VA exceeds a predetermined second lower limit value.

6. A turbocompressor, characterized in that it comprises:

the electric motor system (30) of any one of claims 1 to 5; and

and an impeller (21) connected to the drive shaft (31) of the motor system (30) and serving as the load (21).

7. The turbocompressor according to claim 6,

the turbo compressor (12) is provided in a refrigerant circuit (11) that performs a refrigeration cycle and configured to compress a refrigerant by the impeller (21),

when the turbo compressor (12) IS operated in a region (C) or a surge region (D) where rotating stall occurs, the control unit (60) controls the power supply units (61, 62) so that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value.