If you have had the privilege of participating in motor tests, you may have a deeper understanding of variable frequency technology. Especially those who have used the old test equipment can better appreciate the advantages of variable frequency technology.
Whether it is the inspection test or the type test of the motor, the motor starting process will be involved. Especially in the case where the motor power is relatively large and the grid capacity is relatively small, it will be quite difficult to start the motor without load. Since this is the case during the test process, one can imagine what it is like during the actual operation startup of the motor.
The locked-rotor test is a detection carried out when the motor rotor is in a stationary state, which is used to detect the starting characteristics and overload characteristics of the motor. For power-frequency motors, starting has always been a very crucial factor. Especially in some special situations, due to factors such as working condition requirements or equipment performance constraints, there is often only a power-frequency power source. Of course, power-frequency motors will also be selected.
对于不少的电机厂，特别是新购置或改进的试验设备，也都采用了变频电源，完全解决了电机的起动问题，但是，也有其弊端，也就是不能完全发现电机的性能弱势。曾经有一批双速电机，在制造厂家试验时，未发现异常，但在使用方却出现了在某一个转速下无法起动的事实，进一步检查发现，该电机试验时只进行了一个转速下的起动性能，而未能发现另一转速下电机起动性能的不足，但电机实际使用过程中恰恰是在起动性能相对较差的对应转速下起动。事实上，电机变频起动时非常容易，这也是试验时能起动而工频运行条件下可能出问题的原因。
For many motor factories, especially those that have newly purchased or improved test equipment, variable frequency power supplies are also used, which completely solves the problem of motor starting. However, there are also some drawbacks, that is, it is not possible to fully detect the performance weaknesses of the motor.
There was once a batch of dual-speed motors. During the test in the manufacturing factory, no abnormalities were found. But in the user's place, it was a fact that the motors could not be started at a certain rotational speed. Further inspection revealed that during the test of these motors, only the starting performance at one rotational speed was tested, and the insufficient starting performance of the motors at the other rotational speed was not discovered. However, in the actual use process of the motors, they were exactly started at the corresponding rotational speed with relatively poor starting performance.
In fact, it is very easy to start the motor with variable frequency, which is also the reason why the motor can be started during the test but may have problems under the power frequency operation condition.
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