JP2001190091A - Operation-switching device of induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation-switching device for smooth switching by eliminating the free-run state of an induction motor when switching between an inverter and a commercial power supply as the drive power supply of the induction motor. SOLUTION: For switching from inverter drive to commercial power supply drive, a frequency adjustment part 18 and a voltage adjustment part 17 shift inverter output to a value being detected by a frequency detection part 15 and a voltage detection part 14, the deviation between the inverter output phase by a phase adjustment part 19 and the phase of the commercial power supply being detected by a phase detection part 16 is equal to or less than a specific value, a synchronization completion judgment part 21 judges the completion of synchronization, and a switching command generation part 22 turns on a commercial connector 11 and then turns off an inverter contactor 13. More specifically, by providing a period for turning on the commercial contactor 11 and the inverter contactor 13 simultaneously, the free-run of the induction motor is eliminated, and overcurrent when a reactor 12 is simultaneously turned on is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor operation switching device, and more particularly to an induction motor for switching the operation of an induction motor from inverter operation to commercial operation or from commercial operation to inverter operation (hereinafter referred to as "commercial / inverter switching"). Operation switching device.

[0002]

2. Description of the Related Art FIG. 5 is an explanatory view showing a conventional commercial / inverter switching of an induction motor. The commercial power supply 1 is connected to an induction motor 3 via a commercial contactor 2. The commercial power supply 1 is also connected to the input of the inverter 4, and the output of the inverter 4 is connected to the induction motor 3 via the inverter contactor 5.

In such a configuration, it is assumed that the induction motor 3 is operated, for example, by an inverter. At this time, the commercial contactor 2 is in the off state, the inverter contactor 5 is in the on state, and the induction motor 3 is operated by the drive power output from the inverter 4. Here, when the induction motor 3 is switched from the inverter operation to the commercial operation, for example, generally, first, the output of the inverter 4 is shifted to the voltage and frequency of the commercial power supply, and then the inverter contactor 5 is turned off. The commercial contactor 2 is turned on, and the induction motor 3 is switched to a commercial power supply. Further, at the time of the commercial / inverter switching, the output of the inverter 4 is further generally synchronized with the phase of the commercial power supply 1.

In these switching operations, an interlock is provided by an operation circuit or the like so that commercial power is not directly applied to the inverter output due to an operation delay of the commercial contactor 2 and the inverter contactor 5.

[0005]

In the conventional commercial / inverter switching, an interlock for protecting the inverter is configured so that the commercial contactor and the inverter contactor are not simultaneously turned on, and there is always a period in which the commercial contactor and the inverter contactor are simultaneously turned off. .

Therefore, when the commercial contactor on the commercial power supply side and the inverter contactor on the inverter side are simultaneously turned off, there is no voltage applied to the induction motor, so that the induction motor is in a free-run state, and the frequency and phase are markedly dependent on the load state. There has been a problem that the frequency, voltage, and phase of the output are changed, and the frequency, voltage, and phase are greatly shifted from the commercial power supply after the switching or the inverter output synchronized with the commercial power supply, and an excessive current flows.

The present invention has been made in view of the above points, and provides an operation switching device capable of performing a synchronous operation with an inverter or a commercial power supply after switching to eliminate a free-run state of a motor and smoothly performing switching. The purpose is to do.

[0008]

According to the present invention, in order to solve the above-mentioned problems, the frequency of the commercial power supply is detected in an induction motor operation switching device for driving the induction motor by switching the drive power supply to a commercial power supply or an inverter. Frequency detecting means, voltage detecting means for detecting the voltage of the commercial power supply, phase detecting means for detecting the output voltage phase of the commercial power supply, and detecting the inverter output voltage by the voltage detecting means in response to a switching command from the inverter to the commercial power supply. A voltage adjusting means for shifting the voltage to the voltage of the commercial power supply, and an inverter output frequency detected by an externally set inverter frequency or the frequency detecting means according to a switching command from the commercial power supply to the inverter or a switching command from the inverter to the commercial power supply. Frequency adjusting means for shifting to the frequency of the commercial power supply, Phase adjusting means for shifting an inverter output voltage phase to the commercial power output voltage phase detected by the phase detecting means in accordance with a switching command to commercial power, and a deviation between the commercial power output voltage phase and the inverter output voltage phase Is within a preset range, a synchronization completion determining means for determining completion of synchronization, a first contactor connecting the commercial power supply and the induction motor, and a second contactor connecting the output of the inverter and the induction motor. And the first contactor is turned on and then the second contactor is turned off at the time of a command for switching from the inverter to the commercial power, and the second contactor is turned off at the time of a command for switching from the commercial power to the inverter. Switching command generating means for turning on the first contactor and then turning off the first contactor, and connecting in series with the second contactor. The is first
And an AC reactor for suppressing the inverter output current when the second contactor and the second contactor are turned on at the same time.

According to such an induction motor operation switching device, when the induction motor is driven by the inverter, the frequency adjustment means adjusts the inverter output frequency to a frequency based on an externally set inverter frequency command. The induction motor is driven by the voltage and the phase corresponding to the frequency. Here, when switching from the inverter drive to the commercial power supply drive, first, the frequency adjustment means adjusts the inverter output frequency to shift to the frequency of the commercial power supply detected by the frequency detection means, and the inverter at that frequency The output voltage is changed to the voltage of the commercial power supply detected by the voltage detection means. The phase adjusting means is
The inverter output frequency phase is shifted to the phase of the commercial power supply detected by the phase detection means. When the synchronization completion determining means determines the completion of the synchronization, the switching command generating means turns on the first contactor and turns off the second contactor. At this time, there is a period in which the first contactor and the second contactor are simultaneously turned on. During this period, the current flowing due to the voltage drop between the commercial power supply voltage and the inverter output voltage is suppressed by the AC reactor. Even after the switching from the inverter drive to the commercial power supply is completed, the adjustment by the voltage adjuster, the frequency adjuster and the phase adjuster is continued. Therefore, when there is an input of a switching command from commercial power supply driving to inverter driving, the switching command generating means can immediately turn on the second contactor and turn off the first contactor. Is released, and the inverter output is adjusted based on the inverter frequency command. At the time of switching from commercial power supply driving to inverter driving, there is a period in which the first contactor and the second contactor are simultaneously turned on.
During this time, the current flowing due to the voltage drop between the commercial power supply voltage and the inverter output voltage is suppressed by the AC reactor. Thus, when the drive power of the induction motor is switched, the first contactor and the second contactor do not turn off at the same time, so that the induction motor does not go into a free-run state, and the first contactor and the second contactor do not go off. An excessive current that may flow when the two contactors are simultaneously turned on can be suppressed by the AC reactor.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a basic configuration of an operation switching device for an induction motor according to the present invention. The operation switching device 10 includes a commercial contactor 11 that connects the commercial power supply 30 and the induction motor 50, and an inverter 4
Reactor 12 connecting output 0 and induction motor 50
And an inverter contactor 13. The operation switching device 10 includes a voltage detection unit 14, a frequency detection unit 15, and a phase detection unit 16 connected to the commercial power supply 30.
A voltage adjustment unit 17 receiving an output of the voltage detection unit 14 and an operation output of the voltage operation unit 41 in the control unit of the inverter 40, a frequency adjustment unit 18 receiving an output of the frequency detection unit 15 and an inverter frequency command, A phase adjustment unit 19 that receives the output of the phase detection unit 16 and its own output, an adjustment start determination unit 20 that receives the commercial / inverter switching command, and outputs of the voltage adjustment unit 17, the frequency adjustment unit 18, and the phase adjustment unit 19 A synchronization completion determining unit 21 for receiving the synchronization completion determining unit 21 and a switching command generating unit 22 for receiving an output of the synchronization completion determining unit 21 are provided. The output of the voltage calculator 41 in the controller of the inverter 40 is connected to a PWM (pulse-width modulation) modulator 42, and the output of the PWM modulator 42 is connected to the inverter 40 via a gate driver 43. Have been.

The voltage detector 14 detects the voltage of the commercial power supply 30, the frequency detector 15 detects the frequency of the commercial power supply 30, and the phase detector 16 detects the phase of the commercial power supply 30.
The voltage adjustment unit 17 includes a voltage of the commercial power supply 30 detected by the voltage detection unit 14 based on the output of the adjustment start determination unit 20 and an inverter 40 calculated by the voltage calculation unit 41.
Is adjusted so that the output voltage of the inverter 40 becomes equal to the voltage of the commercial power supply 30 based on the output voltage of Frequency adjuster 1
8 adjusts the output of the inverter 40 to the frequency of the commercial power supply 30 detected by the frequency detection unit 15 or the frequency specified by the inverter frequency command based on the output of the adjustment start determination unit 20. The phase adjuster 19 adjusts the output voltage phase of the inverter 40 to be equal to the voltage phase of the commercial power supply 30 based on the output of the adjustment start determiner 20. The synchronization completion determination unit 21 monitors deviations between the output of the inverter 40 and the voltage, frequency, and phase of the commercial power supply 30 based on the outputs of the voltage adjustment unit 17, the frequency adjustment unit 18, and the phase adjustment unit 19, and Is determined to be complete when the deviation of the data falls within a preset range.
When the synchronization is completed, the switching command generator 22 turns on / off the commercial contactor 11 and the inverter contactor 13.
Performs off control.

Here, the induction motor 50 is connected to the inverter 40
When driven by the frequency adjusting unit 18
Adjusts the output of the inverter 40 to be the frequency specified by the inverter frequency command.
The calculation is performed so that 1 becomes an inverter output voltage corresponding to the frequency. The voltage calculator 41 converts the inverter output command to PW
Output to the M modulator 42, the PWM modulator 42 performs pulse width modulation based on the command, and the gate driver 43 controls the inverter 40. The inverter 40 is connected to the commercial power supply 3
0 is input, and the induction motor 50 is driven by the controlled output voltage via the reactor 12 and the inverter contactor 13.

Switching of the induction motor 50 from inverter drive to commercial power supply drive is started based on a commercial / inverter switch command. When the adjustment start determining unit 20 receives the commercial / inverter switching command, the voltage adjusting unit 17, the frequency adjusting unit 18, and the phase adjusting unit 19 output the inverter output to the voltage detecting unit 14, the frequency detecting unit 15, and the phase detecting unit 16.
Is adjusted so as to shift to the voltage, frequency, and phase of the commercial power supply 30 that has been monitored. When the synchronization completion determining unit 21 determines that the inverter output has been changed to the voltage, frequency, and phase of the commercial power supply 30 by these adjustments, the switching command generating unit 22 first turns on the commercial contactor 11, and then switches the inverter. The contactor 13 is turned off to cut off the inverter output. Thus, the induction motor 50 is switched from inverter drive to commercial power drive. At this time, there is a period in which the inverter contactor 13 and the commercial contactor 11 are simultaneously turned on,
Since the phases of the inverter output and the commercial power supply are substantially the same, switching of the drive power supply for the induction motor 50 can be performed smoothly, and the voltage between the commercial power supply voltage and the inverter output voltage is switched between the inverter output and the commercial power supply. A current flows due to the head, and the current is suppressed by the reactor 12.

Next, when the induction motor 50 is switched from the commercial power supply drive to the inverter drive, since the voltage and phase are adjusted, the inverter output is always switched to the induction motor after the commercial / inverter switching command is input. Is ready to connect to Therefore, the switching command generator 22 first turns on the inverter contactor 13 and turns off the commercial contactor 11. Also at this time, there is a period during which the inverter contactor 13 and the commercial contactor 11 are simultaneously turned on, but the current flowing between the inverter output and the commercial power due to the voltage drop between the commercial power supply voltage and the inverter output voltage is caused by the reactor 12. Is suppressed. Thereafter, the inverter is operated in accordance with the inverter frequency command.

Next, a specific configuration example of the operation switching device 10 will be described. FIG. 2 is a diagram illustrating a configuration example of the operation switching device. 2, the same or equivalent components as those shown in FIG. 1 are denoted by the same reference numerals, and a detailed description thereof will be omitted. The power supply voltage, the power supply frequency, and the power supply phase shown on the left side of the drawing indicate signals representing the voltage, frequency, and phase of the commercial power supply 30 detected by the voltage detection unit 14, the frequency detection unit 15, and the phase detection unit 16, respectively. ing.

A switch 61 for performing a switching operation according to a commercial / inverter switching command is shown. The signal of the power supply frequency and the inverter frequency command are input to the fixed contact of the switch 61, and the movable contact is
2 are connected. The output of the acceleration / deceleration calculator 62 is
The output is connected to the frequency / voltage converter 63, and the output is connected to the voltage calculator 41 via the adder 64. As a result, the frequency signal selected based on the commercial / inverter switching command is frequency-adjusted by the acceleration / deceleration calculator 62,
The frequency signal is converted into a voltage by the frequency / voltage converter 63, and the voltage signal is input to the voltage calculator 41.
The voltage calculator 41 calculates a signal to the PWM modulator 42 such that the inverter output voltage becomes the voltage.

The output of the acceleration / deceleration calculator 62 is also supplied to the adder 6
5 is connected to the angle calculator 66, and the output is input to the voltage calculator 41. The angle calculator 66 calculates the angle signal indicating the phase of the inverter output by integrating the frequency signal.

The output signal calculated for the angle is supplied to a PI (proportion) through an adder 67 for calculating a difference from the power supply phase signal.
The output is connected to an input of an adder 65 via a switch 69. As a result, the proportional integral calculation is performed so that the power supply phase and the inverter output phase match, and the calculated output signal is added to the frequency signal from the acceleration / deceleration calculator 62 as a correction amount.

The signal representing the inverter output voltage calculated by the voltage calculator 41 is connected to a PI controller 71 via an adder 70 for calculating a difference from the power supply voltage signal, and the output is provided via a switch 72. And connected to the input of the adder 64. Thus, a proportional integral operation is performed on the difference between the power supply voltage and the inverter output voltage, and the output is added to the voltage signal from the frequency / voltage converter 63 as a correction amount.

The output of the acceleration / deceleration calculator 62 is connected to a constant speed middle judgment section 73. When switching from inverter drive to commercial power supply drive, the constant-speed medium determination unit adjusts the inverter output from the inverter frequency to the commercial power supply frequency, and determines whether the inverter output has reached the commercial power supply frequency by the adjustment. However, when the inverter output reaches the commercial power supply frequency, it is determined that the speed is constant, and control is performed to turn on the switches 72 and 69.
Thereby, the correction of the voltage and the phase of the inverter output is started. The output of the adder 70 is connected to a voltage adjustment completion determining unit 74. The voltage adjustment completion determining unit 74 detects when the deviation between the inverter output voltage and the power supply voltage falls within a preset range, determines that the voltage adjustment has been completed, and outputs a voltage adjustment completion signal to the switching command generation unit 2.
Output to 2. Further, the output of the adder 67 is connected to the synchronization completion determining unit 21. This synchronization completion determination unit 2
1 detects when the deviation between the inverter output phase and the power supply phase falls within a preset range, determines that synchronization has been completed, and outputs a synchronization completion signal to the switching command generator 22.

The switching command generator 22 receives the voltage adjustment completion signal and the synchronization completion signal, and receives the commercial contactor command for the commercial contactor 11 and the inverter contactor 1.
3 generates an inverter contactor command. The commercial contactor command changes from an OFF command to an ON command when switching from inverter drive to commercial power drive, and changes from an ON command to OFF command when switching from commercial power drive to inverter drive. The inverter contactor command changes from an ON command to an OFF command when switching from inverter driving to commercial power supply driving, and changes from an OFF command to an ON command when switching from commercial power driving to inverter driving. Each of the commercial contactor 11 and the inverter contactor 13 has an auxiliary contact that operates in conjunction with the switching operation of the contactor, and output signals thereof become a commercial contactor confirmation signal and an inverter contactor confirmation signal.

Next, the operation of the operation switching device will be described with reference to a time chart. FIG. 3 is a time chart showing the operation when switching from inverter drive to commercial power supply drive. During the inverter driving operation, the commercial contactor 11 and the commercial contactor confirmation signal are off, and the inverter contactor 13 and the inverter contactor confirmation signal are on. The inverter output frequency is the frequency designated by the inverter frequency command (in the example shown, lower than the power supply frequency), and the inverter output voltage is a voltage corresponding to the frequency. Also,
The voltage adjustment completion signal and the synchronization completion signal are in a state indicating incomplete.

Here, when a switch from inverter drive to commercial power supply occurs according to the commercial / inverter switch command, first, the switch 61 is switched to the side receiving the power supply frequency signal, and the inverter output frequency is set to the outside. The frequency is switched from the current frequency to the commercial power frequency. The acceleration / deceleration calculator 62 accelerates the output frequency of the inverter to reach the frequency of the commercial power supply 30 in the acceleration / deceleration time set by the soft start function, and converts the frequency signal to
The voltage is converted into a voltage signal by the voltage converter 63 and input to the voltage calculation unit 41. As a result, the frequency of the inverter output approaches the frequency of the commercial power supply 30, and the voltage also approaches the voltage of the commercial power supply 30.

When the inverter output frequency reaches the frequency of the commercial power supply 30, the middle speed determining section 73 determines that the vehicle is running at the constant speed, turns on the switch 72, and reduces the inverter output voltage to a predetermined voltage for inverter operation. The inverter output voltage so as to eliminate the deviation between the inverter and the commercial voltage. Further, the constant speed middle determination unit 73 turns on the switch 69, the PI controller 68 operates so as to eliminate the deviation between the phase of the commercial power supply 30 and the frequency phase of the inverter output, adjusts the frequency, and adjusts the frequency of the inverter output. Frequency phase to commercial power 3
Adjust to zero phase.

Next, when the voltage adjustment is completed and the synchronization completion determining unit 21 determines that the deviation between the frequency phase of the inverter output and the phase of the commercial power supply 30 is equal to or less than a certain value, it is determined that the phase synchronization has been completed. As described above, when the adjustment of the voltage and the phase is completed, the switching command generator 22 first turns on the commercial contactor command. Commercial contactor 11 performs an ON operation in response to the ON command. Commercial contactor 11
The ON operation of is confirmed by the operation of the linked auxiliary contact in the commercial contactor 11 to turn on the commercial contactor confirmation signal. The switching command generator 22 turns off the inverter contactor command and turns off the inverter contactor 13 in response to the commercial contactor confirmation signal being turned on. At this time, the gate driving unit 43
Is gated off, and the inverter output becomes zero in voltage and frequency. Thereafter, when the inverter contactor confirmation signal is returned from the inverter contactor 13, the switching operation from the inverter drive to the commercial power supply drive is completed.

In this switching operation, the output of the inverter 40 and the commercial contactor 11 are simultaneously turned on from the time the commercial contactor confirmation signal is turned on until the inverter performs the gate-off operation, but the phases are almost the same. Therefore, the switching of the drive power supply becomes smooth, and a current flows due to a voltage drop between the commercial power supply voltage and the inverter output voltage. The current is suppressed by the reactor 12.

FIG. 4 is a time chart showing the operation when switching from commercial power supply driving to inverter driving. During the commercial power supply driving operation, the inverter contactor 13 and the inverter contactor confirmation signal are off, and the commercial contactor 11 and the commercial contactor confirmation signal are on. The inverter 40 has no output due to the gate-off operation. Also,
During the commercial power supply driving operation, the voltage adjustment and the phase adjustment are continuously performed. That is, the frequency setting is adjusted to the commercial power supply frequency, and the voltage is adjusted to the commercial power supply voltage. Regarding the phase, the switch 69 is turned on, and the PI controller 68 adjusts the deviation between the commercial power phase and the inverter output phase so as to eliminate the deviation.
Operates and the phase is adjusted to the phase of the commercial power supply. In this state, the synchronization completion signal is constantly output, the synchronization control is always performed, and the state can be immediately switched to the inverter drive at any time.

Therefore, when a command to switch from commercial power supply driving to inverter driving is input in this state, an inverter contactor command for immediately turning on inverter contactor 13 and a gate signal are output. This allows
The inverter contactor 13 turns on, the inverter contactor confirmation signal turns on, the commercial contactor 11 turns off, and the commercial contactor confirmation signal turns off. During this time, the output of the inverter 40 and the commercial contactor 11 are simultaneously turned on from the time the inverter contactor confirmation signal is turned on to the time the commercial contactor confirmation signal is turned off. However, even if there is a voltage drop between the commercial power supply voltage and the inverter output voltage, the current flowing therethrough is suppressed by the reactor 12.

When the commercial contactor confirmation signal is turned off,
The phase adjustment and the voltage adjustment are released, and the output frequency of the inverter 40 is adjusted according to an externally set inverter frequency command.

[0030]

As described above, according to the present invention, even when the terminal voltage of the induction motor is switched from the inverter output to the commercial power supply, a period is provided during which the commercial contactor and the inverter contactor are simultaneously turned on. As a result, smooth operation switching can be performed without causing the induction motor to run free. Also, by providing a reactor for the inverter output, it is possible to suppress overcurrent due to the inrush current at the time of switching between the induction motor and the switching, and to operate without overcurrent trip due to the voltage drop between the commercial power supply voltage and the inverter output voltage. It is possible to continue.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an operation switching device for an induction motor according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of an operation switching device.

FIG. 3 is a time chart showing an operation when switching from inverter drive to commercial power supply drive.

FIG. 4 is a time chart showing an operation when switching from commercial power supply driving to inverter driving.

FIG. 5 is an explanatory diagram showing a conventional commercial / inverter switching of an induction motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Operation switching device 11 Commercial contactor 12 Reactor 13 Inverter contactor 14 Voltage detection part 15 Frequency detection part 16 Phase detection part 17 Voltage adjustment part 18 Frequency adjustment part 19 Phase adjustment part 20 Adjustment start judgment part 21 Synchronization completion judgment part 22 Switching command generation Unit 30 commercial power supply 40 inverter 41 voltage calculation unit 42 PWM modulation unit 43 gate drive unit 50 induction motor

Claims (3)

[Claims] 1. An induction motor operation switching device for operating an induction motor by switching a drive power supply to a commercial power supply or an inverter, wherein: a frequency detection means for detecting a frequency of the commercial power supply; and a voltage detection means for detecting a voltage of the commercial power supply. Phase detection means for detecting an output voltage phase of a commercial power supply; voltage adjustment means for shifting an inverter output voltage to the voltage of the commercial power supply detected by the voltage detection means according to a switching command from an inverter to the commercial power supply; Frequency adjustment means for changing the inverter output frequency to an externally set inverter frequency or the frequency of the commercial power supply detected by the frequency detection means by a switching command from the commercial power supply to the inverter or a switching command from the inverter to the commercial power supply, Inverter output voltage level by switching command from inverter to commercial power supply Phase adjusting means for shifting a phase to the output voltage phase of the commercial power supply detected by the phase detection means, and when a deviation between the output voltage phase of the commercial power supply and the inverter output voltage phase is within a preset range. Synchronization completion determining means for determining completion of synchronization; a first contactor connecting the commercial power supply and the induction motor; a second contactor connecting the output of the inverter and the induction motor; When the first contactor is turned on at the time of the switching command, the second contactor is turned off, and at the time of the switching command from the commercial power supply to the inverter, the second contactor is turned on and the first contactor is turned on. Switching command generating means for turning off the first contactor and the first contactor and the second contactor connected in series to the second contactor. Kuta is operation switching device of the induction motor, characterized in that it comprises a, and suppressing AC reactor the inverter output current when turned on simultaneously. 2. The voltage adjustment means, the frequency adjustment means, and the phase adjustment means, wherein the voltage adjustment, the frequency adjustment and the phase adjustment are performed while the induction motor is being driven by the commercial power supply in response to a switching command from the inverter to the commercial power supply. The operation switching device for an induction motor according to claim 1, wherein adjustment is maintained. 3. The frequency adjusting means includes: a switching command generator configured to switch the frequency to the externally set inverter frequency after an off operation of the first contactor performed based on a switching command from the commercial power supply to the inverter. 3. The operation switching device for an induction motor according to claim 2, wherein the adjustment is performed.