Motor phasing

[Joeygr]

I can't figure out motor phasing.

As far as I know, for an asynchronous motor, the phase connection only affects the direction of rotation.

But I've encountered situations more than once where you have a motor, an incremental encoder, a frequency inverter, and only one correct way to connect the phases (out of six possible). If the phases are connected incorrectly, not only does the direction change, but also the speed and current.

Can someone explain why this happens

[Dfcz]

Because in a three-phase network, all phases are always shifted by 120 degrees and always of the same frequency.
And a conventional three-phase asynchronous motor is being tested to operate at a single constant frequency.

And the voltage after the frequency converter has a different frequency and a different duty cycle. Moreover, the phases shift briefly during acceleration and deceleration. Also, the frequency converter may try to prevent the system from oscillating, thereby additionally changing the shift and duty cycle of the pulses. Moreover, if the system has a speed sensor, it may additionally incorrectly detect and adjust speed and acceleration.

To illustrate that the frequency converter-motor-encoder system may "not work correctly", even if the motor is properly connected to the frequency converter.
You can compare a "cheap" system in which the frequency converter can supply high power and low speed to the motor with an "expensive" system that works well under the same conditions.

[Joeygr]

Because in a three-phase network, all phases are always shifted by 120 degrees and always of the same frequency.
And a conventional three-phase asynchronous motor is being tested to operate at a single constant frequency.

And the voltage after the frequency converter has a different frequency and a different duty cycle. Moreover, the phases shift briefly during acceleration and deceleration. Also, the frequency converter may try to prevent the system from oscillating, thereby additionally changing the shift and duty cycle of the pulses. Moreover, if the system has a speed sensor, it may additionally incorrectly detect and adjust speed and acceleration.

To illustrate that the frequency converter-motor-encoder system may "not work correctly", even if the motor is properly connected to the frequency converter.
You can compare a "cheap" system in which the frequency converter can supply high power and low speed to the motor with an "expensive" system that works well under the same conditions.

Thank you for the explanation. But I still don't understand why there is such a difference, since the motor windings are symmetrical. And how can I determine the correct connection?

[Dfcz]

The motor windings are symmetrical. But, everything else is not symmetrical.

It is possible to determine the correct connection only by the method of "scientific poking", that is, by iterating through the connection of the windings.

In particularly critical cases, I take three conventional 36 volt transformers or one three-phase 36 volt transformer, connect it to a conventional three-phase network, and connect the motor. Going through the ends of the windings, I find a connection when the current is minimal and the motor is rotating freely. This does not always give an accurate result, but the motor will not burn out.

[Joeygr]

The motor windings are symmetrical. But, everything else is not symmetrical.

It is possible to determine the correct connection only by the method of "scientific poking", that is, by iterating through the connection of the windings.

In particularly critical cases, I take three conventional 36 volt transformers or one three-phase 36 volt transformer, connect it to a conventional three-phase network, and connect the motor. Going through the ends of the windings, I find a connection when the current is minimal and the motor is rotating freely. This does not always give an accurate result, but the motor will not burn out.

Спасибо. Тоже делал методом научного тыка, но там в одной из конфигураций скорость подачи была такая, что выломало ограничитель

[Dfcz]

Ну, на работающем оборудовании искать правильную фазировку?