- Joined
- Mar 28, 2013
- Messages
- 10
Bernie -
I don't know for sure why the engineers decided to use audible frequencies for their pulse rate on motor drives but the low-end DC PM machines like Sieg sure do - It's right around 1000 Hz. I don't think the technology of the day allowed for higher PWM frequencies, because it would require much faster switching times for the Mosfets and fast recovery diodes. A lot of the newer ones seem to be 25-30khz so are out of the range of human hearing. Now, the SCR controllers run at 60 Hz so they just 'hum'.....
-Pete
I don't know for sure why the engineers decided to use audible frequencies for their pulse rate on motor drives but the low-end DC PM machines like Sieg sure do - It's right around 1000 Hz. I don't think the technology of the day allowed for higher PWM frequencies, because it would require much faster switching times for the Mosfets and fast recovery diodes. A lot of the newer ones seem to be 25-30khz so are out of the range of human hearing. Now, the SCR controllers run at 60 Hz so they just 'hum'.....
-Pete