Sag. 12 vfd. Clutch issues

[Jim Moser]

I had some contactor problems with my sag 12 so ended up bypassing all the Italian wiring and running the motor direct from a vfd and the cluch controll 40 volt DC from the single fase 220, problem is when I engauge the clutches on the higher speed the VFD shuts down with an over current error code. I have the 2 speed motor model and using the low speed windings about 860 rpm, dont seem to have this problem except on the highest speed setting. Seems like some kind of current surge when going up or down on the speed ranges. Anybody know of some settings like a buffer or surge supressor setting in the VFD. There is a gazillion parameters in the VFD, no idea what they are all for?
Any ideas, got no response on the VFD forum page?

Thanks. Jim

 

[Pretzel Logic]

I had some contactor problems with my sag 12 so ended up bypassing all the Italian wiring and running the motor direct from a vfd and the cluch controll 40 volt DC from the single fase 220, problem is when I engauge the clutches on the higher speed the VFD shuts down with an over current error code. I have the 2 speed motor model and using the low speed windings about 860 rpm, dont seem to have this problem except on the highest speed setting. Seems like some kind of current surge when going up or down on the speed ranges. Anybody know of some settings like a buffer or surge supressor setting in the VFD. There is a gazillion parameters in the VFD, no idea what they are all for?
Any ideas, got no response on the VFD forum page?

Thanks. Jim

In my case with a Schaublin 102 and the original 2 speed motor, everyone I've talked to says connect up to the high speed winding only.

 

[Peter from Holland]

I heard somewhere on this board from a person who figured out the electrical diagram from a SAG12 that the clutches are engaged with 40 volts but after a short while they drop the voltage to something less
I hate those wire diagrams
I agree with using 1 speed of the motor only Or program your VFD for 2 motorsettings if possible and swith accordingly Otherwise it is always a compromise

Peter

 

[Jim Moser]

The open circuit voltage from the DC diodes is about 70 volts, it drops to 30 volts when a clutch is engauged but is a pretty instantaneous load on the VFD that I assume causes some current spike that trips the VFD OC fault on the higher speeds. Probably just need to get a bigger VFD to handle the surge but I kind of like using the 860 rpm motor, quiter and smooth so not in a rush but hoping there was some buffering or delay setting for the fault to activate?

 

[Peter S]

What do I know about electric stuff? Very little.

Years ago we built machinery which used magnetic clutches to control stepping of conveyors. When you cut power to a clutch (or a solenoid) you get a spike which travels back and can cause problems.
We fitted varistors across the two wires going to each clutch and solenoid.
In later years the varistors were no longer needed, not sure why