Phase converter for truck hoist

[User Name]

Hey guys, customer bought a 4 post turck hoist for his shop, it has 4 2hp motors on each post. The shop is 240 1ph. The hoist is 240 3ph. Load looks to be about 28 amps. I think these hoists are only available in 3ph. Phase converter time. So, I've used rotary phase converters in the past with pretty good luck. Used American Rotary and North American, both seem like they have a good product.

Company that sold the hoist is recommending a Phase-O-Matic static phase converter, they claim they have good luck with using their 20hp-30hp static converter. I'm skeptical. I've used SPC before, with zero luck. I'm guessing they are grossly oversizing the SPC to run 8hp worth of motors, but I don't know. I feel like if they bump this hoist on and off a bunch of times with a serious load on it, it's just going to pop the capacitors. The static costs $1300, rotary costs $2300. You guys think it's worth pushing the extra $1000 for something I know works? Or have you guys used SPC's on multiple motors that start and stop frequently had it's been fine?

 

[cowski]

From what I understand, SPCs are ideal for motors that "start quickly and infrequently". So good for fans, not so good for hoists. So if they're going to use the hoist often you're probably better off with the rotary.

My only other thought for a cheap option would be a single to three phase VFD, running in V/Hz mode. You'd want to provide a reactor. But that may not be a direction you want to go either...

 

[Jraef]

This is from Phase-a-Matic's info on their SPCs:

IMPORTANT: Static Converters do not produce constant 3-phase power; they “jump-start” your 3-phase motor to run on single-phase power. Be sure to read all information provided.

They go on to warn you that the motor will only produce 2/3 of it's rated HP IF it is a Wye wound motor. Delta wound motors only produce 1/2 of their rated power. I would not expect that to be a good idea on a hoist... unless the motors start off being grossly over sized for the task.

Now, might they have meant "Phase Perfect" and got the names mixed up? Phase Perfect is a type of SPC, but instead of just using capacitors to trick the motor into running at reduced capacity, they actually "manufacture" the 3rd phase with an inverter for just that one phase. That works a lot better and does not reduce the motor's capacity. They are more expensive than the Phase-a-Matic type SPCs, but typically less expensive than using a VFD and if the variable speed is unimportant, as it would be in this situation, it's a better way to go.

But be very careful here. If these are direct traction type lifts (as opposed to hydraulic) and are NOT using a worm drive, they may rely upon the motor back EMF fighting the line when lowering, in order to avoid having the motor run away. You will NOT be able to do that with any type of SPC. If that's the case, you will need a VFD and appropriately sized dynamic braking resistor. But I doubt that is going to be the case here.

 

[hbiss]

Any chance you could get a 3 phase service at that location? That sounds like the best solution for something like this.

-Hal

 

[rambojoe]

I have used phoenix phase converters multiple times with no problems-and the owner is geared to only sell what he knows is correct... Fwiw. He also everytime has upgraded our order to a digital controller for free... Have all your specs and he will tell you what he can do.