Unicorn? 1ph 110v in 1ph 110v out VFD for $140

I have the vfd installed and programmed and ostensibly it works. Ive tried it on a centrifugal switch buffer and the start/run cap grinder motor. It will run both at variable speed.

That said, the buffer in particular has no torque under 45hz. The grinder has significant torque loss as well. I haven't read through all the parameters but did increase the anti stall comp, it did not help. Haven't found a torque comp setting yet.

Now, ignoring the buffer, on this 2 cap grinder motor, should I disconnect the run cap? Jumper past it? Maybe both? I can play around with it but curious what you guys think. For how I use this horizontal grinder I can use it as is. But I can hear one of the caps clicking in and off when I slow it down by hz or just by stalling.

It's also not very responsive to freq changes under 40 hz. Requires 30 just to start turning.

As it stands this might work great for a brushed motor but unless i can figure out how to get more torque and better frequency response at low hz i don't think it's a solution for a belt or disc grinder.

I'll play around with it some more.
 
Thanks for the update - I don't have any advice for you, but will be watching this thread.
 
in particular has no torque under 45hz. The grinder has significant torque loss as well.
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Whats not surprising. Slowing down frequency lengthens the ”dead zone” between power peaks of singlephase sinewave.
 
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Yeah that makes sense. I didn't think it would be so drastic. It's not linear, it's logarithmic.
 
This is what I was talking about when I said it shouldn't work.

All single phase motors will work at a hertz different from the plate. However, any motor needed to deliver power or torque will greatly decrease in efficiency if the frequency changes more than about 15% (about 10 Hz). At 50% reduction (about 30Hz) it should stop working and just create heat. The windings and poles (magnets) are positioned so as to allow the rotor to be pulled efficiently toward the next magnet as the last magnet pushes it away. A normal 2 pole motor needs enough time to allow the pull/push to create torque. A four pole motor might do a tad better because it has less space between each pole ( 90° vs 180°). Still, both need the timing right to run properly.

I would also expect heat to greatly increase as you went beyond 15% deviation from rated hertz.
 
Is there some reason 6 and 8 pole motors seem to only be available in fractional HP?
 
I have been thinking about using one of the DVR setups for a grinder. Huge RPM range, super flat torque curve, precise RPM adjustment (and maintenance). I have it on a Nova DVR lathe and it is magnificent. I presume it would be great in a grinder.

These are the things that drive the drill press Stacy posted a thread about a few weeks ago. The price seems pretty reasonable for a motor/controller combo at that level of power delivery as well.

https://www.amazon.com/Striatech-53010-Intelligent-Reluctance-Controller/dp/B00XCIN2I4
 
I am also surprised there are not some DVR grinder setups. Maybe it just isn't familiar with folks yet. Time will tell.

I am a fan of DC drives for high torque and big motors. I have a Fincor drive that runs any motor from 1 to 20 HP (just change the plug-in HP module). I have several DC motors up to 5HP. The 3HP is a huge beast around 100 pounds, but would be great for some fixed use device .... like a big wet grinder. The 5HP DC motor may get use on a press. I might even be able to add a switch on a control box and switch from one HP size to the other easily to allow use on several devices..
 
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