quick question about 3 phase motors with VFD

[Kevin W Johnson]

I think Kevin cleared it up but I do have a question but I will get to that in a moment.

Most VFDs have a low voltage (in the case of the FM50 it is 12v, many use 24v) auxillary circuit that can be used to "tell" the VFD to cut power to the load (motor). You could think of this like a low voltage switch that runs a relay to turn high voltage power on and off to a machine, like the Long Ranger setup that turns on a dust collector when a blast gate is opened. It can also handle reversing on machines like lathes. The diagrams Kevin put up show this, besides a main on and off button you can also wire in emergency stop buttons or switches like a large slap switch or for example micro-switches in the doors or connected to the foot brake of bandsaws.

Here is my question since Kevin or someone else may be able to correct me. My understanding is the low voltage (low current) auxillary circuit we are discussing would NOT work with the machines standard mag switch. My understanding of this is because the voltage and or current is not high enogh to keep the mag switches contactor closed, in this case the magnetic switch would "see" the 12V as a cut power situation and open and remain open. Can comeone confirm whether the use of a mag switch in this manner will or will not work?

In the diagram I posted, the magnetic contactor (coil) is being operated by the incoming 230v, we're simply using the contacts to make or break the 12v signal that tells the VFD to turn the motor on and off.

[Van Huskey]

In the diagram I posted, the magnetic contactor (coil) is being operated by the incoming 230v, we're simply using the contacts to make or break the 12v signal that tells the VFD to turn the motor on and off.

AHHHH, I see says the blind man!

[Michael W. Clark]

Thanks, I see there is a lot of capabilities with the VFD's. It seems like if I put the mag switch before the VFD (line side), then I get the benefits of the mag switch and loose the SPC.

This completely has nothing to do with the TS application, but If you were using the VFD to control motor speed, then I suppose your control signal would go into this low voltage signal input? Its not just on/off, its variable 0-12V, 4-20mA, 0-24, etc? I've designed some industrial DC systems with VFDs, but I'm mechanical and haven't gotten into the details of which wire goes where. I may not "need" to know it, but I sure like having an understanding so I'm not completely lost when the electricals are talking.

Mike

[Van Huskey]

Thanks, I see there is a lot of capabilities with the VFD's. It seems like if I put the mag switch before the VFD (line side), then I get the benefits of the mag switch and loose the SPC.

This completely has nothing to do with the TS application, but If you were using the VFD to control motor speed, then I suppose your control signal would go into this low voltage signal input? Its not just on/off, its variable 0-12V, 4-20mA, 0-24, etc? I've designed some industrial DC systems with VFDs, but I'm mechanical and haven't gotten into the details of which wire goes where. I may not "need" to know it, but I sure like having an understanding so I'm not completely lost when the electricals are talking.

Mike

For variable speed on the FM50 you can use the key pad to vary the frequency OR it has inputs to use a 10Kohm pot. This circuit is a 10V circuit seperate from the on/off/reverse circuit.

[Jerome Stanek]

If you use a roto phase you can run multiple machines from it and you can use your mag switch as before. We just put a sub panel in and run cicuits to each machine.

[Kevin W Johnson]

If you use a roto phase you can run multiple machines from it and you can use your mag switch as before. We just put a sub panel in and run cicuits to each machine.

Both ways have pro's and con's. Depending on the equipment being used though (ie. bandsaws, lathes, drill presses), having the variable speed that comes with having a VFD is really nice.

[Van Huskey]

Both ways have pro's and con's. Depending on the equipment being used though (ie. bandsaws, lathes, drill presses), having the variable speed that comes with having a VFD is really nice.

Don't forget soft start, motor braking and reversing(lathes and mills).

[mreza Salav]

Ok, I have ordered the one from Factorymation and it's on its way to me.
Now reading another thread, I came across the following post by Rick which makes me worrried:

http://www.sawmillcreek.org/showthre...27#post1938527

The manual for my bandsaw does say that it has a motor brake which makes it stop within 10 seconds. The saw has a foot brake too but as far as I have checked it there is no micro-switch, just a drum type brake (at the back of lower wheel). Is the VFD going to work with this 3-phase motor?!