Vfd powered from rpc?

[jar944]

I have a 20hp rpc and a bunch of various vfds powering my woodshop 3ph equipment with no single motor over 9hp/6.6kw.

I just picked up 24" 15hp planer (17hp with the feed and table motors incuded)


So now I find myself trying to figure out how to power the thing. The rpc isn't going to start it (at least in its current delta only starter)

I could look for a star/delta starter, or a soft start and possibly make one of those work. However I was wondering if I could just use a 15hp vfd running off the rpc for a soft start.

My last choice is a motor swap down to 10hp, though that may be the cheap/easy option by using a 2nd hand surplus motor.

 

[PCustoms]

Why stack a rpc and a VFD?

 

[jar944]

Why stack a rpc and a VFD?

Soft start, smaller vfd

 

[930dreamer]

Have you tried the 20 hp rpc and another machine running and then starting the new planer?

 

[micromind]

That motor cannot be started Y - ∆. It can be started part-winding on 208 - 230 but I doubt it'd help much.

I've never seen a VFD supplied but a rotary phase converter, I doubt the VFD would tolerate the voltage imbalance.

 

[jar944]

That motor cannot be started Y - ∆. It can be started part-winding on 208 - 230 but I doubt it'd help much.

I've never seen a VFD supplied but a rotary phase converter, I doubt the VFD would tolerate the voltage imbalance.

Ha.. I never even bothered to look at the lead count on that data plate.

 

[Stuart in MN]

Assuming this is a residential electrical service, your utility may have regulations that limit motor sizes - a 15hp motor may too big.

 

[jar944]

Assuming this is a residential electrical service, your utility may have regulations that limit motor sizes - a 15hp motor may too big.

What they don't know...

 

[wyliesdiesels]

What they don't know...

as the transformer feeding your house blows the cutouts...

 

[jar944]

as the transformer feeding your house blows the cutouts...

Lol, well that was the point of the soft start.

If it blows from ~70 amps I have more problems.

 

[jar944]

Have you tried the 20 hp rpc and another machine running and then starting the new planer?

I have not

 

[wyliesdiesels]

Lol, well that was the point of the soft start.

If it blows from ~70 amps I have more problems.

the issue isnt with the running amps. its with the in-rush current which can be anywhere 4x-8x FLA

 

[jar944]

the issue isnt with the running amps. its with the in-rush current which can be anywhere 4x-8x FLA

Right, which is why I was looking for a soft start option Or ideally a 10 second ramp via vfd.

 

[Stuart in MN]

as the transformer feeding your house blows the cutouts...

Or the neighbor's lights dim.

 

[American Locomotive]

A VFD likely won't enjoy running off an RPC. RPCs typically have wildly imbalanced voltages (even just a few volts makes a big difference), and the rectifier inside the VFD won't like that. You'd be better off just running a bigger VFD directly off single phase power.

 

[jar944]

A VFD likely won't enjoy running off an RPC. RPCs typically have wildly imbalanced voltages (even just a few volts makes a big difference), and the rectifier inside the VFD won't like that. You'd be better off just running a bigger VFD directly off single phase power.

Yeah, I'm in the shop right now trying a 20hp vfd on single phase. Certainly won't develop 15hp but if it works I'm out nothing other than swapping things around.

Edit.

Working well enough on a 20hp vfd on single phase.