I don't understand how vfd detects speed when we are running in open loop control (sensorless).
For me only possible way;
during auto tuning it calculates resistance and inductance values of motor which means it knows equivalent circuit of motor. while running, the vfd also knows current and stator frequency so it can calculate slip from equivalent circuit. From slip, we can find actual speed since we know stator frequency.
What is your opinion ? My thoughts are correct or close to correct ?
Thanks in advance.
For me only possible way;
during auto tuning it calculates resistance and inductance values of motor which means it knows equivalent circuit of motor. while running, the vfd also knows current and stator frequency so it can calculate slip from equivalent circuit. From slip, we can find actual speed since we know stator frequency.
What is your opinion ? My thoughts are correct or close to correct ?
Thanks in advance.