You may want to use a 15-20 hp VFD and connect it to a breaker sub panel so you can connect all additional 220v 3ph machinery off one VFD.
Contributor
You may want to use a 15-20 hp VFD and connect it to a breaker sub panel so you can connect all additional 220v 3ph machinery off one VFD.
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Can that even be done? My impression has always been that a VFD needs to go direct to a motor which is why a 3 phase slider with scoring would need two of them. But perhaps I'm mistaken about that...Originally Posted by John Erickson
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
That is my understanding as well. No switching between a vfd and the motor it controls. A rotary or digital (Phase Perfect) phase converter is what you want for powering multiple machines.
I suspect the least expensive and simplest solution given that the o.p. is ok with less power would be a static converter for each motor.
Last edited by Kevin Jenness; 03-24-2022 at 8:51 PM.
Contributor
I find this interesting as the RPC I built for my neighbor several years back is almost totally quite. The starter motor is connected directly to the rotary with a coupler, no belts
Member
No.. well you can do it once.
Member
You can do this, but it requires a certain level of discipline & thought - or automation - that few small shop users will find acceptable. (Tho' when you throw phase conversion in with it, I'd advise the Mr. Leiferman to run away.) Details are beyond the scope of this thread, but basically motor '1' has to be completely stopped and braking off before you disconnect it from the VFD and then connect motor '2' - each via its own starter relay. It is called "multiplexing" and once upon a day past, I was hired to fix an abominably crappy OEM implementation of this (1 VFD >> 5 motors). Timing is everything. Oh, and all the motors will need the same basic specs: poles, voltage, FLA, etc..
You can also hardwire 1 VFD to multiple motors if the VFD has the proper capacity - - I've seen a 250Hp VFD connected to 50 x 5Hp motors - all running at once. They will all receive and so run at the same frequency.
Member
Most high quality, properly sized VFDs will simply fault and require reset before next attempt. The DC bus voltage goes nuts when the load comes off and then slams back on.
Member
This is one of those I need to address but have never gotten to it things. I have 2 different possible 10hp idler motors that I can use. An old cast iron frame motor and a much newer steel framed motor. Both have Zircs on the shaft bearings to lube the bearings. I have tried molly grease and lithium grease which will quiet the motors for a few hours then they will slowly come back to noisy. They both might just have bearings that are going bad but I think I am probably not using the correct type of grease? The grease I use is pretty much what ever is in the grease gun at the time. Is there a light weight grease or oil that I am supposed to be using? I do pull the back plug before I apply grease through the zirc. Just that there is a back plug kind of makes me think that I am supposed to be using something with a thin enough viscosity that it would run out with out the back plug. I have done some Googling on the subject of electric motor lubrication but have never found a definitive answer.
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Last edited by Michael Schuch; 03-25-2022 at 12:59 PM.
Contributor
Swap out existing bearing for new sealed ones. Plug the holes where the zerks are. Part of your hum could be caused by your capacitor bank.
[OP]
Member
An update: I bought a Vevor 10 hp VFD from Mr. B. to try on the main 7.5 hp 3p motor. Hooked it up to a 30 amp 220 v breaker and the motor and fiddled with the settings for about an hour and got it to run nicely. My hope is that I can mount this vfd for the main as well as another smaller one for the scoring motor in an enclosure, and just run remote contact switches to the vfd's to start and stop. Will update again if I can get that figured out.
10hp vfd cost $200. I have heard these cheap vfd's can muck up motor bearings, and since the motor is 25 yrs old, will take it apart and put in some cool ceramic bearings since the old bearings are probably original, though they sound fine.
I have also they can mess with the motor, but my impression is that is more common when running the motor at a speed other than it was designed for, which I won't be doing. So have to cross my fingers on that.
Contributor
A 10hp VFD for $200? I hope it works well for you, but a quality 3hp VFD is usually around $200.
A VFD should have no effect on bearings, maybe windings but not bearings. Bearings don’t care if you’re running slower than designed, but too much speed will do it. But even that, woodworking motors don’t spin fast enough to really matter.
Don’t use ceramic bearings, just use normal greased rubber sealed steel bearings.
Member
The issue is currents generated in the motor shaft by the vfd that grounds through the bearings. It's a known issue with vfds and the reason for ad hoc grounding brushes and insulated bearings on some applications.
[OP]
Member
Mike Schuch
I followed your suggestion, bought a 10 hp 7.5 kw vfd for the 7.5 hp main motor, and a smaller one for the 1.2 hp scoring. - Vevor VFD's - and they run the motors fine when started via the VFD's integrated keyboard. I want to use remote contact switches to turn the vfd's on and off, but cannot make any sense of the wiring diagram supplied with the vfd. Do you know of any instructions for general VFD remote switching?
Last edited by Mike Leiferman; 05-19-2022 at 11:10 PM.
Contributor
Could you post a link to these 10hp VFD’s for $200?
Never mind, found it. How can these be quality at $200? Experiences anyone?
Last edited by Matt Day; 05-19-2022 at 9:00 PM.
[OP]
Member
Attached my guess at wiring diagram for remote stop start of Vevor vfd.
any suggestions welcome
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