JPH05168278A - Three-phase dc brushless motor - Google Patents

Abstract

PURPOSE:To prevent damage of a switching element, etc., due to an induced current at the time of reversing by turning OFF all switching elements when a speed command becomes near '0' of a speed thereby to feed all induced currents generated in an armature winding in a direction for charging a power source when a rotor is reversely rotated by an external force. CONSTITUTION:The three-phase DC brushless motor comprises a speed setter 50 and a comparator 52. The setter 50 is set to a predetermined speed range V0 near a speed '0' including a speed '0'. The comparator 52 compares V1 of a speed command 1 with a set speed V0, and judges ¦V1¦<V0 to output a stop signal S. A controller 3 so outputs a signal to drivers 28, 30 as to simultaneously turn OFF all transistors Tr1-T6 when the signal S is output. As a result, all the transistors Tr1-T6 are completely turned OFF, and an inverter 12 is protected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a three-phase DC brushless motor which controls a switching element of an inverter based on a rotor magnetic pole position to switch a current and a phase of an armature winding.
It is about data.

[0002]

2. Description of the Related Art A conventional three-phase DC brushless motor has a structure shown in FIG. Reference numeral 1 in this figure
Reference numeral 0 is a DC power source, 12 is an inverter unit composed of a transistor three-phase bridge circuit, 14 is a rotor, 16 (16a, 1
6b and 16c) are three-phase armature windings that are stators.
The rotor is a block-shaped or comb-shaped lumped rotor having a built-in permanent magnet and serves as a field.

The inverter section 12 has three transistors T _r1 , T _r2 , T _r3 as input side switching elements connected to the + side of the power source 10 and three transistors connected to the − side of the power source 10. And transistors T _r4 , T _r5 , and T _r6 as switching elements on the output side. Each transistor T _{r1 to} T _r6
In reverse parallel, the diode for flywheel D ₁ ~
D ₆ is connected.

The connection points of the paired transistors T _r1 and T _r4 , T _r2 and T _r5 , and T _r3 and T _r6 are three-phase armature windings 16a to 16a.
It is connected to one end of 16c. Each winding 16a-16c
The other ends of are connected to each other, and finally a star-connected armature winding 16 is formed.

A rotor magnetic pole position detector 18 includes a permanent magnet plate 20 directly connected to the rotor 14, three magnetic sensors 22 arranged at equal intervals so as to surround the permanent magnet plate 20, and outputs of these sensors 22. And a distributor 24 that determines the magnetic pole position of the rotor 14 based on.

A control unit 26 selectively turns on / off the transistors T _{r1 to} T _r3 based on a signal indicating the rotor magnetic pole position output from the distributor 24, and also based on the speed command, the transistor T _r1. selectively chopping control the _r4 ~T _r6. The difference (V ₁ −V) = V ₂ between the speed command 1V ₁ supplied from an external device and the speed signal V fed back from the control unit 26 is supplied to the control unit 26 as the speed command 2V _2. Is entered.

The control unit 26 controls the input side transistors T _{r1 to} T _r3 and the output side transistors T _{r4 to} T _r6 separately by the drivers 28 and 30. That is, the input side transistors T _{r1 to} T _r3 are turned on / off so as to be kept on or off within a predetermined rotor magnetic pole position range.
Controlled off. The output side transistors T _{r4 to} T _r6 are chopping-controlled by, for example, a PWM (pulse width control) method so as to have a duty ratio corresponding to the speed command 2V ₂ .

Of course, the transistors T _{r1 to} T _{r6 which} are on / off controlled or chopped are sequentially changed according to the change of the rotor magnetic pole position. As a result, the armature winding 16 generates a rotating magnetic field to rotate the rotor 14.

[0009]

2. Description of the Related Art In a motor constructed as described above, an external force may be applied to the rotor 14 to forcibly reverse the rotor. For example, when this motor is used to drive a blower fan of an external unit of an air conditioner, the wind of the outside air drives the fan in the opposite direction to reverse the motor. By this reversal, the motor functions as a generator and generates an induced voltage of opposite polarity in the armature winding 16.

At this time, if all the transistors T _{r4 to} T _r6 on the chopping controlled side are off or in a state close to off, for example, when the transistor T _r1 is on, a current i ₁ flows through the winding 16a due to an induced voltage. , This current i
₁ is divided into currents i ₂ and i ₃ of the windings 16b and 16c, and is refluxed so as to flow to the diodes D ₂ and D ₃ .

On / off controlled transistors T _r1 ~
This is because T _r3 is controlled so as to be sequentially turned on in synchronization with the rotor magnetic pole position so that the on periods do not overlap. If this induced voltage is large, the diodes D _{1 to} D ₃
Alternatively, the transistors T _{r1 to} T _r3 may be destroyed.

Further, the currents i ₁ , i ₂ ,
If the transistor T _r1 is turned off while i ₃ is flowing, a current corresponding to this current i ₁ will flow from the power source 10 through the diode D ₄ due to the inductive component of the winding 16 at the moment of turning off. , The energy regenerated by the winding 16 is released through the diode D ₄ . Therefore bipolar voltage of the battery 10 rapidly increases, transistor T _r1 ~
There is a possibility that T _r6 and the diodes D _{1 to} D ₆ may be damaged.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents the switching element and the like of the inverter part from being damaged when the motor is reversed by an external force. It is an object of the present invention to provide a three-phase DC brushless motor which can be prevented.

[0014]

According to the present invention, this object corresponds to an inverter portion constituted by connecting three-phase bridges of switching elements, a rotor magnetic pole position detector, and a rotor magnetic pole position. A three-phase DC brushless motor that switches the current and the phase of the armature winding based on the rotor magnetic pole position, and the speed command is zero speed.
It is characterized in that it comprises command speed discrimination means for discriminating that it is within a constant speed range in the vicinity and outputting a stop signal, and based on the stop signal, the control unit turns off all switching elements of the inverter unit. And three-phase DC
A three-phase DC having a brushless motor
Achieved by a brushless motor.

[0015]

1 is a block diagram of an embodiment of the present invention. In this figure, the same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will not be repeated.

2 is different from that of FIG. 2 in that a speed setter 50 and a comparator 52 are provided. The speed setter 50 includes a speed 0 and has a constant speed range V ₀ near the speed _0.
To set. The comparator 52 compares the speed command 1V ₁ with this V ₀ , determines that | V ₁ | <V ₀ , and outputs the stop signal S. Instead of this speed command 1V ₁ , the speed command 2V ₂ may be compared with V ₀ .

When the stop signal S is output, the control unit 26 outputs a signal to the drivers 28 and 30 so as to turn off all the transistors T _{r1 to} T _r6 at the same time. As a result, all the transistors T _{r1 to} T _r6 are completely turned off, and the inverter section 12 is protected.

According to the present invention, when the speed command 1V ₁ is in the constant speed range ₀ to V ₀ near the speed 0, all the transistors T _r1.
.About.T _r6 is turned off, and the intended purpose cannot be achieved by turning off only the transistors T _{r1 to} T _r3 on the input side. This is because the control unit 26 sends a signal to the driver 3 so as to rotate it in the forward rotation direction based on the speed command 2V _2.
This is because the voltage of both electrodes of the power supply 10 rapidly increases when the output voltage is 0. The reason is as follows.

At this time, since any of the transistors T _{r4 to} T _r6 is chopping, for example, if the transistor T _r4 is chopping, the current i ₁ flowing at the moment when it is turned on is at the next moment when it is turned off. Will flow back through the flywheel diode D ₄ . During this time, the currents i ₂ and i ₃ of the other windings 16b and 16c are flowing out from the negative electrode of the power source 10 via the diodes D ₅ and D ₆ , so that the voltage between both electrodes of the power source 10 rapidly increases. ..
Therefore, the transistors T _{r1 to} T _r6 and the diodes D _{1 to} D are
_This is because there is a risk of destroying ₆ .

In the above embodiment, the output side transistor T
By chopping control _r4 through T _r6 by controlling the current in the armature winding 16 mode - controls the Tatoruku. However, the voltage of the power supply 10 is made variable and the output side transistor T _r4
It is also possible to control ON / OFF of ~ T _r6 at the same time as the input side. The present invention also includes such a thing. The switching element instead of the transistor T _r1 through T _r6, the may be other elements such as a thyristor as a matter of course.

[0021]

As described above, according to the present invention, all the switching elements are turned off when the speed command is close to the speed of 0. Therefore, when the rotor is reversely rotated by an external force, it is generated in the armature winding. The induced current that flows only flows in the direction of charging the power supply. Therefore, it is possible to prevent the switching element and the like from being damaged by the induced current at the time of reverse rotation and protect the inverter section.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional device

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 DC power supply 12 Inverter unit 14 Rotor 16 Armature winding 18 Rotor magnetic pole position detector 26 Control unit 50 Setter 52 Command speed discrimination means

Claims (1)

[Claims] 1. An inverter unit comprising switching elements connected in three-phase bridge, a rotor magnetic pole position detector,
A three-phase DC brushless motor having a controller for chopping or on / off controlling a predetermined switching element corresponding to the rotor magnetic pole position and switching the current and phase of the armature winding based on the rotor magnetic pole position. In the above, a command speed discriminating means for discriminating that the speed command is within a constant speed range near a speed of 0 and outputting a stop signal is provided, and the control unit is based on the stop signal, and the control unit controls all switching elements of the inverter unit. A three-phase DC brushless motor characterized by turning off.