JPS5883591A - Braking method for induction motor - Google Patents

Abstract

PURPOSE:To obtain a smooth braking control by controlling the frequency of a variable frequency voltage applied to an induction motor and consuming the current by a discharging resistor while controlling the current generated by the motor at this time, thereby decelerating the motor at the constant deceleration torque. CONSTITUTION:In case that a brake control command is inputted when an operating induction motor 3 becomes free-running upon opening of a main power source contactor 2, a brake controller 12 is operated immediately by a contactor 9. The output side contactor 4 of the brake controller 12 is closed after confirming the remaining voltage cancellation of the motor 3 from the brake control command. Since the motor 3 is operated as an induction motor after the contactor 4 is closed, the output frequency of the brake controller is lowered, thereby discharging the power back current to the brake resistor 10. The power back current is detected by a CT 5, is compared with the set reference value of a current setter RH 6, and the controller 12 is controlled in frequency by the deviation.

Description

[Detailed Description of the Invention] a) Description of the Technical Field The present invention provides a method for controlling a free-running induction motor with a constant deceleration torque when the main power source of the induction motor trips due to a power outage or failure of the main power source. If you want to decelerate, use a power source other than the main power source, such as 411 power source for safety equipment.

A variable frequency voltage is applied to the induction motor from a sound power source such as a low-voltage power source using a frequency converter.

An induction motor with a control function that allows the induction motor to act as an induction generator by controlling the frequency, controlling the current generated and guiding it to a discharge resistor for consumption to reduce the rotational speed of the induction motor with a constant deceleration torque. Related to AC DB Control Device for Electric Motor b) Description of Prior Art Conventionally, a braking method using a DC power source has been adopted for emergency stopping of a wound induction motor. This method is one of the induction motor
A method of applying DC voltage to the next terminal and guiding the secondary induced voltage to an external secondary resistor to mechanically adjust the secondary resistor to consume current and reduce the rotational speed of a wound induction motor. Met. In the case of squirrel cage induction motors, DC braking was performed by adjusting the DC current applied to the stator windings.

However, in either case, when the DC power is turned on, the current is large, the effective utilization rate of the motor windings is poor, and the entire range of sb
It was difficult to control smoothly.

C) Purpose of the Invention The present invention provides a hI variable frequency braking system 111 as shown in FIG.
2 is set up to generate a free-running conductor sound: SVC is applied, the output frequency of the brake control device is controlled, and the induction motor acts as an induction generator to generate a power-back current. It is designed to lead the current to the braking resistor lo and release the current at a constant rate to reduce the speed. Unlike the conventional method described above, direct current *S is not required, and the current is directly controlled by phase and current feedback. To provide a braking method for an induction motor that can perform smooth braking control without imparting torque shock to other equipment because the frequency is controlled so that a necessary constant deceleration torque can be obtained.

d) Structure of the invention 1I81 is a block diagram showing an embodiment of the invention. The induction motor 3 is operated by the main power supply unit 1K, but if this main power supply @lt1 becomes unable to operate due to a failure or a stoppage, and if you want to smoothly decelerate the induction motor, first contact it with a brake control command. Turn on the brake power supply contactor 4 to establish the braking power supply, and confirm that the contactor 2 of the main power source device 1 is open. After the residual pressure of the induction acid motor disappears, the brake power supply contactor 4 is turned on and the variable frequency voltage is applied to the induction motor. is applied to perform split!Ih control.The main circuit configuration of the brake control power source is the input side transformer 411, this K yaw)te secondary voltage 50
V to about 500 V is selected and supplied to the inverter 12. The inverter 12 is composed of 8CRs for forward conversion, DCL, 8CRs for reverse conversion, and ACL. I7 is a CT for detecting the inverter output current phase, 16 is a CT for ejecting the induction motor current phase, 5 is a CT for detecting the current of the induction motor, and 10 is a braking resistor that discharges the current that is powered back from the induction motor. It is for the purpose of

Braking control power supply control/1” road configuration is S for l111M transformation
Cl phase control unit 13 and output voltage setting 1i
ni4, an SCR phase control unit 8 for inverse conversion, a frequency control unit 7, a current phase comparison unit 15, and a power supply (for back current standard setting) tH6.

e) Effect of the invention In FIG. 1, the induction motor 3 in operation is connected to the main four-source contactor 2.
When the brake is released and a brake control command is input at the same time, the brake control device is activated by the e-contactor 9 immediately.

The output voltage of the brake control device is controlled by the forward conversion 8c phase control unit 13 and the -pressure setting RHI4.
If four motors are required, adjust B11 to the pressure (50 to 500V) K.

Furthermore, the output frequency of the braking control device is set close to the rated operating frequency of the induction motor.

The braking control device output current is DB via the current limiting accelerator.
The resistor 10 is being discharged.

After receiving a braking control command and confirming that the residual voltage in the induction motor 3 has disappeared, the output contactor 4 of the side motion control device is turned on.

After the contactor 4 is turned on, in order to cause the alligator conductive motor 3 to function as an induction generator, the output frequency of the braking control device is lowered and a current for power backing is discharged to the braking resistor 10, and braking control is performed.At this time, the power back '1 flow is detected by the CT 5 and compared with the set base value of the current setting RI 46. After that, the current is manually set as a reference for the output frequency of the brake control device, and frequency control is performed to maintain a constant current.

Further, the '1 current phase detection C''T16.17 and the current phase comparison unit 15 determine that the induction motor is switched to the induction motor, and act to enter braking control from that point on.

f) Other Embodiments In the main text, the explanation has been made assuming that when only the main power supply equipment fails or a power outage occurs, the power supply is supplied from a healthy AC power source other than the main power source, such as a safety power source or a low-voltage power source.

Here, another embodiment will be described in which all AC power sources are tripped and braking control is performed from the battery power source.

Figure @2 is its block diagram. From 1 to 9, the same part numbers as in Figure 1 are omitted.

Battery ・21 to inverter 2 according to the braking control command
The built-in C is charged to 0. When the inverter 2I is on duty and applies a variable frequency voltage to the induction motor 3, the frequency is lowered and the induction motor 3 becomes an induction generator, and the power-backed current overcharges C and raises the voltage by 1. It is detected by the voltage detection unit 18, and the control element drive unit 19 is turned on and off to control the braking resistor 5i.
A current is applied to the voltage to suppress the rise in voltage.

In this embodiment, the DC voltage increase during braking control does not have an adverse effect on the batch 17-21, and the battery 21
is the point where almost no energy is consumed.

g) Overall effect As explained above, unlike the conventional (K-hydraulic type), the present invention is capable of constant torque braking at several Hzt from around the rated operating frequency of a symmetrical induction-motor, and the amount of control can be freely controlled. It has the characteristic that it can be set and smoothly starts and brakes, and the applicable range is applicable to induction motor braking control for driving all types of equipment, not just blowers and pump drives, regardless of whether it is low voltage or high voltage motors. Of course, it is also possible to use it during normal operation stoppages, and it provides excellent controllability.

[Brief explanation of drawings]

Figure 1 shows a block diadem showing one embodiment of the present invention, and Fig. 2 shows a block diadarum showing another embodiment of the invention. 1 041m main 1 source device 2 main 1 source contactor 31! Motive 4 Output side contactor for DB control device 5 CT for power back current detection 6 RH for power back current setting 7 Frequency control unit 8 Phase control unit for inverse conversion SCR 9 Input end contactor for DB control device IQ DB resistance transformer 11 transformer 12 inverter unit 13 11i transformer 1ji14 SCR phase control unit 14 inverter voltage setting RH 15-current phase comparison unit 16 induction motor current phase detection C'r17 DB
Control device output 1st flow phase detection CT 18 Overpressure detection unit 19 Control element drive control unit 20 Inverter unit 21 Battery Fig. 1 Fig. 2

Claims (1)

[Claims] In the case where a failure occurs in the main power supply of the induction motor and it is desired to decelerate the induction motor with a constant deceleration torque, a variable frequency voltage is applied to the induction motor from a power source other than the main comfort source using a frequency converter. A method for braking an induction motor, which is characterized by controlling the frequency of the induction motor, controlling the current generated by the induction motor at that time, and causing it to be consumed by a discharge resistor to reduce the rotational speed of the induction motor with a constant deceleration torque.