JP2001069788A - Driving method for induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable method for driving an induction motor through simple structure while reducing power consumption. SOLUTION: A motor 10 is driven with a voltage significantly lower than a rated voltage under no-load and the driving current is monitored by means of a current sensor 14. When the driving current increases, a decision is made that a load is applied and the driving voltage of the motor 10 is returned back to the rated voltage. The low voltage is set in the range of 1/10-1/5 of the rated voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method of an induction motor for controlling an operation state and a stop of the induction motor.

[0002]

2. Description of the Related Art Conventionally, the operation state and stop of an induction motor have been performed by turning on and off switches and the like via various sensors. Also, for example, in the case of a machine tool, the motor is rotated under no load until the tool hits the processing device,
When a tool comes into contact with a workpiece to apply a load, and when the load has an abnormality, the abnormality is detected and the driving of the motor is stopped. In addition, sensors are also used to detect other abnormalities,
The warning was displayed.

[0003]

In the case of the above-mentioned conventional technology, a large number of sensors are required for controlling the motor, the detection circuit and the like are complicated, and the whole apparatus is complicated and the reliability is not high. Was. Also, a large amount of power is consumed for driving the motor in a no-load state.

The present invention has been made in view of the above-mentioned problems of the prior art, and has a simple structure, low power consumption,
It is an object of the present invention to provide a method for driving an induction motor with high reliability.

[0005]

A method of driving an induction motor according to the present invention drives the motor at a low voltage that is significantly lower than a rated voltage when no load is applied, and the driving current at that time is measured by a current sensor or the like. When the monitored drive current increases, it is determined that a load has been applied, and the drive voltage of the motor is returned to the rated voltage and the motor is driven. The low voltage is 1/10 to 1 of the rated voltage.
/ 5 voltage.

Further, there is provided a method of driving an induction motor in which a power factor or a phase of the motor is monitored and a drive voltage of the motor is adjusted between a rated voltage and the low voltage by changing the power factor or the phase. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show a drive circuit of an induction motor according to an embodiment of the present invention.
The three-phase induction motor 10 is connected to a 200-V three-phase AC power supply via a voltage regulator 11 such as a three-phase sliderac and a switch 12. A current sensor 14 is provided on the wiring for driving the motor, and an output of the current sensor 14 is a phase converter 16 for detecting a phase of a driving current of the motor 10.
The power is input to a power factor converter 16 for detecting a power factor and a current converter 20 for detecting a current.

[0008] The phase converter 16 and the power factor converter 18 are further connected to the drive wiring of the motor 10 so that the phase and the power factor can be detected. Further, the detection outputs of the phase converter 16, the power factor converter 18, and the current converter 20 are input to the operation control circuit 22. Further, the detection outputs of the phase converter 16 and the power factor converter 18 are input to the standby alarm device 24. The outputs of the power factor converter 18 and the current converter 20 are connected to a standby alarm setting device 24 and an operation alarm setting device 26.

The operation of the induction motor driving device according to the present embodiment is as follows.
When the motor 10 operates, the load 28 is applied to the motor 10.
And the motor 10 operates under a predetermined control. Here, when the motor 10 is in a no-load state, for example, when the tool is broken and the load is eliminated, or when the load is eliminated due to the end of machining, as shown in FIG. Because of large fluctuations, the phase converter 16
Alternatively, this is detected by the current converter 20, and this detection signal is output to the operation control circuit 22 and the standby-side alarm setting device 26, and an alarm of no-load operation is issued.

Further, during a no-load operation in a standby state, for example, from the end of a work to the next work, in order to suppress power consumption when the motor 10 is rotated at no load, the above-mentioned no-load operation detection signal is used. The control circuit 22 causes the voltage regulator 11 to lower the drive voltage from 1/10 to 1/5 of the rated voltage. Then, the current converter 20
, The drive current of the motor 10 is monitored. As shown in FIG. 2, even at a low voltage, the load current of the motor 10 depends on the size of the load 28, so that the power consumption can be significantly reduced by reducing the drive voltage during the monitoring period. When the load 28 is applied from the no-load state, the load current increases. When the power factor converter 18 or the current converter 20 detects this under a predetermined condition, the operation control circuit 2
2 raises the drive voltage to the rated voltage via the voltage regulator 11.

According to the driving method of the induction motor of this embodiment, when the load 28 is in a no-load state, the driving voltage of the motor 10 is drastically reduced, and the driving current at that time is monitored. In addition, power consumption can be greatly reduced. Furthermore, without using various sensors,
Since the state of the load 28 is detected by monitoring the drive current, accurate detection is possible and the detection device can be simplified. In addition, the monitoring of the operation state of the motor 10 can be easily detected by monitoring the phase and the power factor in addition to the load current of the motor, and it is possible to accurately and safely drive the motor with a simple configuration. Become.

The present invention is not limited to the above-described embodiment, and the application of the motor is not limited.
The setting of the driving voltage can be appropriately performed.

[0013]

The method of driving an induction motor according to the present invention monitors the load state of the motor without reducing the drive voltage and using a complicated sensor, and performs control to return to the rated voltage when a load is applied. , With a very simple configuration,
This enables energy-saving motor drive. Further, the operating state of the motor can be accurately detected with a simple configuration. Furthermore, it can be easily incorporated into existing circuits, and the device is inexpensive.

[Brief description of the drawings]

FIG. 1 is a block diagram of a drive device for an induction motor according to an embodiment of the present invention.

FIG. 2 shows an induction motor (2.2 k) according to an embodiment of the present invention.
5 is a graph showing a drive voltage, a load current, a power factor, and a phase converter output voltage of w.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Induction motor 11 Voltage regulator 12 Switch 14 Current sensor 16 Phase converter 18 Power factor converter 20 Current converter 22 Operation control circuit 24 Standby alarm setting device 26 Operation alarm setting device

Claims (3)

[Claims] In a state where a load is not applied, the motor is driven at a low voltage which is significantly lower than a rated voltage, and a driving current at that time is monitored. A method for driving an induction motor, characterized in that the drive voltage of the induction motor is returned to a rated voltage and the motor is driven when it is determined that the motor is driven. 2. The method of driving an induction motor according to claim 1, wherein said low voltage is a voltage of 1/10 to 1/5 of a rated voltage. 3. The motor according to claim 1, wherein a power factor or a phase of the motor is monitored, and a drive voltage of the motor is adjusted between a rated voltage and the low voltage by changing the power factor or the phase. Driving method of induction motor.