JPH03207201A - Controller for electric vehicle - Google Patents

Abstract

PURPOSE:To protect an induction motor, when there is a non-rotating induction motor, by taking a difference between a value obtained by equally dividing an inverter output current into a plurality of groups and the value of current flowing through a group of induction motors. CONSTITUTION:A bearing current detecting section 12 compares one phase current of one induction motor, detected through a current sensor 11, with 1/4th, for example, of same phase inverter 3 current detected through a current sensor 4. The bearing current detecting section 12 isolates a circuit breaker 2 when the absolute vate of thus detected difference exceeds a predetermined level. When an induction motor 5 provided with the current sensor 11 can not rotate, current concentrates to the induction motor 5 and the output of the current sensor 11 exceeds over 1/4th of the output current from the inverter 3. Consequently, the circuit is interrupted and the induction motor 5 is protected. The induction motor associated with the current sensor 11 or a group of induc tion motors can also be protected in a similar manner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a VVVF inverter device for an electric vehicle,
In particular, the present invention relates to an electric vehicle control device suitable for protecting an induction motor when the induction motor is not rotating.

[Conventional technology]

A motor current control method in a conventional VVVF inverter control device will be explained with reference to FIG.

A plurality of three-phase induction motors 5 are driven by one inverter unit [13], and there is a speed sensor 6 for detecting the rotational speed of the rotor of the three-phase induction motor.

The current sensor 4 is inserted into each phase output of the inverter device, and the control calculation unit 5 adjusts the output voltage, current, etc. of the inverter device so that the effective value of the output of the current sensor 4 matches the command value. Control frequency.

That is, the control calculation unit 8 only controls the sum of the currents of a plurality of induction motors, and there is no method for monitoring the current sharing of the individual induction motors.

(Science of electric cars 1987, V o L 4
0 Na 2 2 1 page, Electric Car Science 1984, V
(See pages oL37 & 83o) Furthermore, it is assumed that multiple induction motors rotate at almost the same number of rotations, and rotational abnormalities other than slipping and skidding are treated as abnormalities in the speed sensor 6, and abnormal speeds are treated as abnormalities in the speed sensor 6. Control is performed by ignoring. [Problems to be Solved by the Invention] The above-mentioned prior art does not take into consideration the protection of the induction motors when some of the plurality of induction motors become non-rotating due to stiff shafts or brake failure. Since the inverter device controls the output current to be constant,
There is a problem in that current concentrates on the induction motor that is not rotating, causing the coil of the induction motor to overheat and burn out.

An object of the present invention is to protect the induction motor by cutting off the circuit when there is a non-rotating induction motor.

[Means to solve the problem]

In order to achieve the above object, a circuit is provided to detect current imbalance between a plurality of induction motors, and the circuit is cut off when an imbalance occurs.

[Effect]

The current of one of the multiple induction motors is detected, and this is compared with a value obtained by equally dividing the inverter output current by the number of induction motors, and if the difference exceeds a certain value, the circuit is cut off.

As a result, when there is an induction motor that is not rotating, the circuit is cut off and the inverter device no longer passes current, thereby preventing overheating and burnout of the coil of the induction motor.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. One inverter device 3 drives four induction motors 5. A current sensor 4 is provided for each of the three phases on the output line of the inverter device 3, and the current effective value calculation unit 7
An effective value is determined from the AC output of the current sensor 4 and is used as a feedback signal to the control calculation unit 8. The control calculation section 8 controls the output voltage, current, and frequency of the inverter device W3 so that the feedback signal and the output of the current command section 9 are the same.

In the present invention, in addition to the above, a current sensor 11 that detects the current of one phase of one induction motor, a current sharing detection section 12, and an operation section 13 of the circuit breaker 2 that disconnects the inverter device 3 from the overhead wire are provided. Ta.

The current sharing detection unit 12 compares the current of one phase of one induction motor detected by the current sensor 1l with a quarter of the inverter current of the same phase detected by the current sensor 4, and calculates the absolute value of this difference. When the value exceeds a certain value, the circuit breaker 2 is disconnected.

Therefore, if the induction motor equipped with the current sensor 11 does not rotate, the current will concentrate on this induction motor.
The output of the current sensor 1l becomes more than a quarter of the inverter output current and the circuit is cut off.

Also. If an induction motor other than the induction motor equipped with the current sensor 11 stops rotating, the current will concentrate on the non-rotating induction motor, so the current of the induction motor equipped with the current sensor 11 will be equal to the inverter output current. It becomes less than one quarter and the circuit is cut off.

According to this embodiment, by adding one current sensor, abnormal rotation of all induction motors operated in parallel can be monitored simultaneously, and if there is an induction motor that is not rotating, the circuit can be cut off. By doing so, it is possible to prevent heating and burnout of the coil of a non-rotating induction motor.

In the embodiment, the current of one induction motor and the output current of the inverter are compared, but it is also possible to consider two or more induction motors as one group and compare them on a group-by-group basis.

Further, even when slipping or skidding occurs, the current of the sloping induction motor becomes larger than one-fourth of the inverter output current, so it is possible to detect slipping and skidding using the same circuit.

〔Effect of the invention〕

According to the present invention, abnormal rotation of an induction motor is detected,
Since the circuit can be cut off, it is effective in preventing overheating and burnout of the coil due to non-rotation.

It also has the effect of detecting and protecting when slipping or skidding.

[Brief explanation of drawings]

FIG. 1 is a flowchart of one embodiment of the present invention, and FIG. 2 is a conventional flowchart. Engineering: pantograph, 2: circuit breaker, 3:
- Inverter device, 4... Current sensor, 5... Three-phase induction motor, 6... Speed sensor, 7... Current effective value calculation unit, 8... Control calculation unit, 9... Current command Part, 1o
...Gate drive unit, 1l...Current sensor. Figure 1

Claims (1)

[Claims] 1. In a variable voltage variable frequency inverter device that drives a plurality of induction motors, a value obtained by equally dividing the inverter output current into a plurality of induction motors or a plurality of groups, and a value that equally divides the inverter output current into a plurality of induction motors or a group of induction motors. An electric vehicle control device comprising a device for detecting an abnormal rotation of an induction motor based on a difference between the current value and the current value. 2. The electric vehicle control device according to claim 1, wherein the circuit is cut off when an abnormality is detected in the rotation of the induction motor.