MartinBruha
Electrical
- May 8, 2010
- 4
Hi guys,
I work now with an inverter feeding a synchronous machine (load-commutated). The characteristic of the firing angle as a function of stator current is usually constant up to certain level and then it starts to fall.
In this case the firing angle is rising at the beginning with the current and later with high current then falling again.
I heard that the reason might be to eliminate harmonics. I just wonder.. My imagination was that the ideal firing angle is 180 degrees. Of course, you cannot drive this angle because of the commutation notch and the time to renew to blocking capability of the thyristor. Usually we don't drive with firing angle over 160 degrees. On the other hand I would expect that the lower firing angle on the inverter side, the worse power factor (cos phi) and the lower torque.
Do you have any explanation?
Martin
I work now with an inverter feeding a synchronous machine (load-commutated). The characteristic of the firing angle as a function of stator current is usually constant up to certain level and then it starts to fall.
In this case the firing angle is rising at the beginning with the current and later with high current then falling again.
I heard that the reason might be to eliminate harmonics. I just wonder.. My imagination was that the ideal firing angle is 180 degrees. Of course, you cannot drive this angle because of the commutation notch and the time to renew to blocking capability of the thyristor. Usually we don't drive with firing angle over 160 degrees. On the other hand I would expect that the lower firing angle on the inverter side, the worse power factor (cos phi) and the lower torque.
Do you have any explanation?
Martin
