Thyristors or FETs for motor drive
Thyristors or FETs for motor drive
(OP)
I'm working on a new drive for a universal motor. Previously we have used triacs for simple turn on/off and speed control. It was suggested to me that MOSFETs or IGBTs may be more economical and produce less heat. Any opinions out there on which to use? Our motor draws about 20 amps at 115 VAC and produces a lot of dv/dt.





RE: Thyristors or FETs for motor drive
An induction motor would let you reduce the dv/dt a bunch if that has any advantage for you.
RE: Thyristors or FETs for motor drive
Disadvantages of universal motors: Not very reliable, maintenance needed, commutator sparks a lot sometimes, considered low-tech.
So it is more a question of deciding which motor to use. Throwing in something else than a triac without changing motor type will not get you anywhere.
Gunnar Englund
www.gke.org
RE: Thyristors or FETs for motor drive
Sound like sticking with the triacs is the way to go.
RE: Thyristors or FETs for motor drive
FETs and IGBTs on the other hand tend to go pop fairly quickly if either the maximum rated voltage or current of the device are exceeded even for an instant. This can be a problem with mains connected motors, unless some sort of fairly elaborate protection is provided. That all adds to cost and complexity.
My own experiences with something similar, were with a range of laboratory centrifuges. Long term reliability of both motor and the controller were never very good. I had more luck when I had a chance to redesign and up rate the controller. The single triac was replaced with back to back SCRs, but the motors still had a short life.
RE: Thyristors or FETs for motor drive