JPH0656344B2 - Induction motor torque characteristic measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a torque characteristic measuring device for an induction motor, which records a starting torque characteristic curve.

(Prior Art) Problems in designing and manufacturing an induction motor include insufficient starting torque and crawling phenomenon, which cannot be confirmed by a load test near the rated speed. Therefore, as a test generally used, there is a method of actually recording and measuring the speed-torque characteristic.

As a torque characteristic measuring device for a starting torque characteristic T of an induction motor as shown in FIG. 3, a shaft torque meter 2 and a load device 3 are connected to an induction motor 1 as shown in FIG. It is often adopted to record the measurement result using the -Y recorder 4. As the load device 3, a flywheel, an eddy current type brake, a DC generator or the like is used, and the rotation speed detector 5 is connected to the shaft end thereof.

In any case of the load device 3, when the change of the rotation speed is made fast, that is, when the load is made light and the acceleration of the induction motor 1 is made fast to shorten the measurement time, the torque curve recorded in the XY recorder 4 is obtained. Deviates from the actual torque curve T as shown by the curve 1 shown by the broken line in FIG.

This is because the torque required for accelerating the shaft system GD ² on the side of the induction motor 1 from the shaft torque meter 2 appears after being reduced to the output of the shaft torque meter 2. On the contrary, when the speed is decelerated from the rated speed for the measurement, the deceleration torque is added and appears as T.

In order to prevent this, it is necessary to make the acceleration and deceleration times as long as possible to reduce the above effects. However, if the load is increased and the measurement time is lengthened, the induction motor that has a starting current several times the rated current may burn, and if the load is excessively increased, the induction motor will stall. It will be burned out.

For this reason, the load device 3 is provided with speed control, the acceleration / deceleration is kept constant, the measuring time is gained without stalling any induction motor having any torque characteristic, and the influence on the above-mentioned measured torque value is reduced. The way is done.

(Problems to be Solved by the Invention) However, the shape of the rotation speed-torque characteristic of the induction motor is not constant, and there are various shapes. For example, in the rotational speed-torque characteristic shown in FIG. 2, the output torque T of the induction motor 1 is almost constant in the low speed range A, but is high in the high speed range B.
In the vicinity of, the change in the torque T with respect to the change in speed is very large.

Therefore, if the acceleration changes from the stop to the rated speed with a constant acceleration, the recording error in the vicinity of the high speed range B becomes large. If the speed change in the vicinity of the high-speed range B is such that it can be ignored, the whole measurement time becomes very long, the winding temperature rise of the induction motor becomes remarkable, and the change of the torque characteristic due to the increase of the secondary resistance. Appears.

As a countermeasure against this problem, a method of changing the speed by providing a speed generator with a speed setter according to the shape of the torque characteristics of the induction motor can be considered, but there are many types of torque characteristics, speeds, etc. , It is almost impossible to match with each other as a general-purpose test device.

The object of the present invention is to accurately record the XY recorder even when the torque characteristics of the induction motor are greatly different in the low speed region and the high speed region, and do not adversely affect the induction motor due to the extension of the test time. An object is to provide a torque characteristic measuring device for an induction motor.

[Structure of the Invention] (Means for Solving Problems) A torque characteristic measuring device for an induction motor according to the present invention applies a load to the induction motor via a shaft torque meter by a load device capable of speed control, and the shaft torque thereof. In the measuring device that measures the rotation speed-torque characteristic of the induction motor by the output of the meter,
A control system for increasing the speed of the induction motor by the load device at a constant speed change rate, and detecting the torque change rate from the output of the shaft torque meter, and suppressing the speed reference voltage change of the load device by this torque change rate signal. And a control system.

(Operation) In the present invention, when the torque of the induction motor enters a region where the torque suddenly increases, the sudden increase in the output of the shaft torque meter is taken out as a rate of change voltage by the absolute value circuit via the differentiator.
The absolute value of the change rate voltage is used as the speed command value of the speed control circuit to be added as a correction signal to the output of the lamp circuit in accordance with the polarity that suppresses the change in the rotation speed by the switching circuit.

As a result, the rotational speed slowly increases only when the output torque of the induction motor is greatly increased or decreased, and the measurement can be automatically performed in the minimum necessary measurement time.

(Example) The present invention will be described below with reference to an example shown in FIG.
In FIG. 1, also in the torque characteristic measuring device of the present invention, the shaft torque meter 2 and the load device 3 are connected to the induction motor 1, and the load device 3 has a rotation speed detector 5 at the shaft end.
The case where the DC machine 6 having the above is used is shown. The measurement result of the shaft torque meter 2 is recorded by the pen writing XY recorder 4.

The DC machine 6 which is the load device 3 has a control system SP ₁ for increasing the speed at a constant speed change rate. The control system SP ₁ receives the speed reference signal S, determines the speed reference by the ramp circuit 7, and inputs the output of the ramp circuit 7 to the speed control circuit 11
DC device 6 via thyristor-Leonard device 12 via
Control the speed.

In addition to the control system SP ₁ , the DC machine 6 also includes a control system SP ₂ that suppresses a change in the speed reference voltage of the control system SP ₁ . This control system SP ₂ receives a rapid speed change in the speed increasing or decelerating process of the induction motor 1 by the output of the shaft torque meter 2 and detects it as an increase in the output of the differentiator 8. The absolute value of the change rate voltage of the differentiator 8 is taken out by the absolute value circuit 9 and is added as the output correction signal of the ramp circuit 7 by the switching circuit 10 in accordance with the polarity for suppressing the change in the rotation speed.

Next, the operation of the induction motor torque characteristic measuring device according to the present invention configured as described above will be described. In FIG. 1, when conducting the test while increasing the rotation speed of the induction motor 1,
First, the DC motor 6 rotates the induction motor at a low speed in the direction opposite to the normal rotation direction, and then the power is turned on. The torque of the induction motor 1 changes little, and in a substantially constant region such as the low speed range A in FIG. 2, the rotations of the induction motor 1 and the DC motor 6 gradually increase in accordance with the speed reference set in the ramp circuit 7. Going up.

However, when the torque rapidly increases in the high speed range B of FIG. 2, the output of the shaft torque meter 2 suddenly increases and the differentiator 8
It appears as an increase in output. The absolute value of this rate of change voltage is taken out by the absolute value circuit 9, the contact 10a of the switching circuit 10 is closed to match the polarity that suppresses the change in rotational speed, and it is added to the output of the ramp circuit 7 as a correction signal to determine the speed of the speed control circuit 11. Use as command value. As a result, only when the output torque of the induction motor 1 is drastically increased or decreased, the rotation speed of the DC motor 6 is slowly increased, and the measurement can be automatically performed in the minimum necessary limited time.

On the contrary, when conducting the test while reducing the speed of the induction motor 1, the contact 10b of the switching circuit 10 is closed to increase or decrease the torque to suppress the decrease in the rotation speed.

In the embodiment shown in FIG. 1, the DC device 6 is used as the load device 3, but this proposal can be applied to any load device capable of performing speed control.

[Effects of the Invention] As described above, in the present invention, in addition to the function of controlling the speed change to be constant, the torque change rate is detected from the output of the shaft torque meter, and the speed reference voltage of the load device is detected by the torque change rate signal. By configuring to suppress the change, even when the torque characteristic of the induction motor is largely different in the low speed region and the high speed region, the moving speed of the pen of the XY recorder can be kept substantially constant and more accurate recording can be performed. You can Further, since the rotational speed is suppressed only in a necessary portion, it is possible to prevent the burnout and the measurement error caused by the increase in the winding temperature of the induction motor due to the extension of the test time.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a torque characteristic measuring device for an induction motor according to the present invention, FIGS. 2 and 3 are torque characteristic diagrams for an induction motor, and FIG. 4 is a conventional torque characteristic measuring device. It is a circuit diagram. 1 ... Induction motor 2 ... Axial torque meter 3, 6 ... Load device, DC machine 4 ... XY recorder 7 ... Lamp circuit 8 ... Differentiator 9 ... Absolute value circuit 10 ... Switching circuit 11 ...... Speed control circuit 12 …… Thyristor Leonard device SP ₁ …… Constant speed change control system SP ₂ …… Suppression correction control system

Claims (1)

[Claims] 1. A measuring device for applying a load to an induction motor via a shaft torque meter by a load device capable of speed control, and measuring the rotational speed-torque characteristic of the induction motor by the output of the shaft torque meter. And a control system for increasing the speed of the induction motor at a constant speed change rate by the: and a control system for detecting the torque change rate from the output of the shaft torque meter and suppressing the speed reference voltage change of the load device by this torque change rate signal. An apparatus for measuring torque characteristics of an induction motor, comprising: