Schaublin 125-CNC retrofit.

RotarySMP wrote:

Good point. Didn't think of that. Although given the that a variator is a pretty imprecise system, if you pulse the variator speed change motor at a fast enough rate, that may not even show up on the surface finish.

You need to make sure that your bang-bang PID has enough hysteresis to not pulse the motor _too_ fast.

Trying to use a relay to drive an inductive load with 1kHz PWM is a way to destroy a relay.

andypugh wrote:

Trying to use a relay to drive an inductive load with 1kHz PWM is a way to destroy a relay.

I did make a THC that used two relays to deive a DC motor and it worked for a while ... till one of the contacts got stuck and sent the torch sky high !

please consider, this is a 4/6 pol Motor from the 70s. It will have insul class B, if you have very much luck evtl. D. But it won't be designed for vfd use.

Yes, I tried running the spindle motor on my aciera mill from the 70s on a VFD, it worked only for a couple of weeks before the motor gave out.

Aciera wrote:

Yes, I tried running the spindle motor on my aciera mill from the 70s on a VFD, it worked only for a couple of weeks before the motor gave out.

I have been running the original motors on my 1964 Holbrook lathe and (probably) 1970s Harrison milling machine on VFDs for many years now with no issues. Possibly Brook Motors used a different insulation to the Aciera supplier?

I have been running the original motors on my 1964 Holbrook lathe and (probably) 1970s Harrison milling machine on VFDs for many years now with no issues. Possibly Brook Motors used a different insulation to the Aciera supplier?

I know there are people out there who have been running motors with isolation class B on VFD's for years. I guess what I'm trying to say is that using a VFD on motors with isolation class lower than F can indeed destroy the motor. So really it comes down to how badly it's going to hurt to replace that motor.

Wondering if those using a VFD in their home shop have used a AM radio to get a feel about the amount of radiated electrical noise emitted ?

VFD's are noisy devices that is why the manuals tell us to follow proper grounding and filtering practice. Usually interference comes from installations that have been poorly executed. The most annoying problem I have is that the filters sometimes trigger the RCD.