Question about VFD for 3 or 5 HP 3 PH motor

[Ken Vick]

I bought a used Zefam 16" jointer a few days ago that has a 3 PH motor.  It is located about 400 miles away at present. The seller can't see a motor info plate so I am not sure of the HP.  I have asked him to measure the current draw but his ammeter is on the fritz so it hasn't happened yet (or ever?)  Looking at other used Zefam jointers, I suspect it is 5 HP.  I don't have access to 3 PH so I can't measure the current draw after I get it in Lewiston, NY.  It will be shipped in a few weeks and John TenEyck will receive this 1600 pound monster at my house and put it into my shop (what a great friend!) because I will be in Florida until late March.  My options seem to be some type of phase converter or to replace the motor.  I have seen a number of VFDs for 3 HP but only a couple for 5 HP that take a single phase input and they were more expensive than a new single phase 5 HP motor.  What would you do?  Ken

[TDKPE]

Not many options here.

You could just buy a single-phase 5 hp motor (cheap from Grizzly), but you'd also almost certainly need a single-phase motor control, too.

You could replace the (presumed) 5 hp motor with a 3 hp single-phase, and probably be able to use the same motor control, as long as the control voltage is or can be set for 240V.

You could find a single-phase input 5 hp VFD, or use a 7.5 hp VFD and run it on single-phase power. No motor control needed, as the VFD is the motor control.

Or buy a rotary phase converter, which is probably the most expensive option at close to $1k, but will allow you to run other 3-phase machines on it, since you no longer have 3-phase power (and if you need a 16" jointer, your needs are far above those of the average hobbiest). The magnetic motor control will still be usable, and that's a cost that has to be considered.

Cheapest is probably a 3 hp motor, reusing the existing motor control. Only you would know if that's adequate for a 16" jointer and the work you intend to do with it. It may be getting close to a toss-up with a 5 hp single-phase motor plus new motor control vs VFD, and the VFD would allow smoother operation as you're retaining the 3-phase motor.*

Most costly would be a purchased rotary converter, unless you start adding machines, and you only have to extend the 240V 3-phase circuit to additional units.

*Single-phase motors pulse, like a one-lunger engine. Single-phase motors with run capacitors (most 3 hp and up) also pulse, but with two out-of-phase windings, sort of like a Harley vee-twin, as they're really two-phase motors with the second phase 'created' through the time-shifting of the wave form via the run capacitor. Three-phase motors have constant output torque, and constant input power (the sum of the power between each phase conductor pair at any time in the cycle is constant, which is why it's both generated and used that way).

[EvilTwin]

It seems to me that once you get above 3 hp, the options narrow and the price goes way up.  Depending on how the motor is mounted, it may be more economical to try and find a used single phase if that would work.  Other options might be a rotary converter, at least that would be available to run other machinery or a static phase converter, though those generally are a poor second choice since they make the motor run on two phases.   

You may be able to get away with a 3 hp converter, even if the motor hp is greater if you program the vfd with a set ramp up time so it doesn't get to full speed for several seconds and avoids the heavy current draw at startup.  Knowing the current draw of the motor would certainly be a help with that.

[BloomingtonMike]

http://www.ebay.com/itm/NEW-HIGH-QUALITY...SwB09YEBXN

4.0kw 5hp 220V single phase in Huan Yang VFD - $169 shipped

Guy using one on a Bridgeport showing how he hooked it up: https://www.youtube.com/watch?v=Ln0UW8RJVSI

[Ken Vick]

Thanks everyone for all the info and especially Mike for specifics on a inexpensive VFD and video of how to  install it.  I still trying to get the current draw and am going to offer to pay for a clip-on ammeter that he can keep in exchange for getting the current draw for me.  I have no complaints about the seller, however.  He is has been great offering to put on skids for me and to get it into the truck with a fudge lift when it arrives at his shop.  Thanks again.  Ken

[Ken Vick]

What is with this new software that Woodnet uses.  I tried to write one word and it substituted "fudge".  I tried to edit it to fix it and it persists but I think you get the drift.  Ken

[BloomingtonMike]

Id just get it ordered and shipping and worry about it when you get to it. Most you are out is a 5hp baldor, leeson, WEG, or marathon motor if you want an amazin motor.

You did verify it is 220V and not 440V?

Again either way get her moving before you loose the deal. It wont matter much a few amps either way. That drive is rated 4kw 5.3 hp.  You wont come near that fla in use even with a chiwan motor.

[JGrout]

it is a nanny filter and it is all forked up 

[Ken Vick]

Mike, I sealed the deal on the jointer the day the owner replied that he still had it and it was still for sale.  In talking to him, I learned that someone else was going to look at it the next day.  The pics in the ad and understanding that the owner had replaced this 8' long jointer with a classic piece of old iron that had shorter beds and better fit his shop convinced me that this was what I had been looking for and I shouldn't waste time making the deal.   I asked if I were to over-night him a check for the full asking price and if that would make me the owner and he said it would.  The next day he acknowledged that the jointer was mine and he has been a big help getting it ready to ship.  We won't be ready to receive it for another couple weeks so the shipping is being delayed until then.  He said the other guy had a fit that he sold it but he had told the guy that the first guy showing up with money was the owner.  

I won't actually be in a position to fire it up until late March or early April when I get back from Florida but I will get the VFD you suggest and have it on hand so that I don't have to wait on it when I get back up here.  Thanks a lot.  Ken

[TDKPE]

I still trying to get the current draw and am going to offer to pay for a clip-on ammeter that he can keep in exchange for getting the current draw for me.  

Don't bother.  That will only get you the unloaded current, which may be very low if it has a run capacitor (like less than 1/3 the rated current), or as much as 60% or so of the rated current, but in either case, you won't know what the rated current is.  Even if you could load the motor, you won't know how much you're putting on it.  And the current will depend on the voltage.  Lotta unknowns.  The nameplate is the only thing that will give you anything useful, though you can put a budget current allowance based on the rated HP and the table in the NEC.