# Phase conversion - 22.8 HP crane



## ByronDC10 (Jul 26, 2014)

I'm looking to convert single phase to three phase to accommodate a 22.8 HP overhead crane.

The crane is an R&M QXDk20-TON x 34 ft.

I've been quoted two products for the conversion... one is a RotaDyne rotary phase converter, and the other is a phase perfect PT-380. The Phase Perfect product is obviously the better product, but it is almost double the price.

I was told that if the crane has any internal electronic components or VFD's for speed control that we can -not- use the Rotadyne, and will need to go the more expensive route.

I would assume that the crane does use VFD's and/or electronics for control judging by the spec. It mentions "adjusted accel time" for the bridge speed... probably an internal VFD?

The client is willing to pay for whatever product we need to make this work, but I don't want to sell him something more expensive than is actually required.

Can anyone shed some light on this? Why exactly will the RotaDyne not work in these circumstances, and what would be my best route for cost and functionality?

Thanks.


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## retiredsparktech (Mar 8, 2011)

ByronDC10 said:


> I'm looking to convert single phase to three phase to accommodate a 22.8 HP overhead crane.
> 
> The crane is an R&M QXDk20-TON x 34 ft.
> 
> ...


Isn't three phase available in the area?
Even if the customer got a real good deal on this crane, why buy something that can't be used.
A 20 ton bridge crane is not a small item. Single phase VFD's are not available, that large.
Even if, there's some kind of a phase converter out there, the lifting ability has to be derated.


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## ByronDC10 (Jul 26, 2014)

It's an existing building that only has single phase power. Yes, I do find it strange that a commercial facility of this size doesn't have three phase power, but it is what it is, unfortunately.

The high voltage 3-phase line is across the road about 200 yards away and it just isn't plausible to have it brought in at this point which is why we are looking into phase-converter options. I am confident that the Phase Perfect PT380 will do the trick (as mentioned in my previous post), but I just wanted some clarification on my original questions.


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## telsa (May 22, 2015)

There are enough issues to have this sent off to tech support// the EEs.

ANY TIME you are lifting heavy materials in a work space -- every facet of the gear has to be PERFECT.

NO WAY can you resolve this matter by way of an Internet forum.

Just too many risks.

Kick it 'up stairs' for a properly engineered solution.

Anything involving cranes, hoists, elevators, etc. is in a whole new 'zone.' 

You're not in Kansas any more. Any screw ups can kill somebody.

Your proposed 'solutions' don't "get 'er done." Not by a long shot. 

Rotary phase converters are NOT suitable for this application. Get 'everybody' on the phone.

You will hear plenty.


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## JRaef (Mar 23, 2009)

You will need to know EXACTLY what s inside of the crane controls first. If the "adjust accel time" is because it has a soft starter, you cannot use the Phase Perfect product. On the PP, it uses two legs from your single phase service, then the third leg is created just like a VFD, using rectification and an inverter. So that leg is a PWM DC output that motors act upon as if it is AC. For Soft starters that time their SCR firing based on the incoming sine waves, the fact that two of the phases are 180 degrees out instead of 120 degrees and the third is PWM DC makes them misfire and short the SCRs very quickly. I know the PP literature makes it appear that it is a "clean balanced sine wave suitable for any 3phase load" but they choose their words very carefully. They never say it works with any 3 phase _controller_. I've seen numerous soft starter users learn this lesson the hard way.

And who told you that you can't use the RPC? The crane mfr? I would check with them, and/or the RPC mfr because that statement is generally not correct. There are a couple of TYPES of "static" phase converters that don't play well with electronics, and some cheaper rotary converters are a kind of hybrid that uses more capacitors in the circuit to avoid having to use an over sized idler (the 3 phase motor that is spinning to generate the 3rd leg). But not all do that and the rotary types that don't are usually fine feeding a VFD. But there are different types of rotary converters, so you can't generallize. 

Another aspect of this, leading to having to see exactly what is in the crane, is that with any kind of phase converter, you should not allow your controls, i.e. starters and relays etc., to be fed from the manufactured leg. So to be safe, you will need to go through the control circuits to make sure control power is tapped off of the "real" legs.


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## ByronDC10 (Jul 26, 2014)

Thank you JRaef.. that actually makes sense. I know my best course of action right now is to get ahold of the crane manufacturer, but so far talking to someone who is willing to answer my questions has not been successful. I'm just going to have to be persistent.

The owner of the building admits it was a mistake to not bring in 3-phase power when it was built 15 years ago. We are trying to do this properly with the resources available.

Any other thoughts or ideas are still welcome.. thanks.


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## JRaef (Mar 23, 2009)

From an eBay ad for the same crane:



> This is a R&M 20 Ton Overhead Crane Kit x 25Ft Span less the steel Beam.
> 
> *CRANE KIT CONSISTS OF:*
> One (1) RM 20 Ton Electric Wire Rope Hoist with Motorized Trolley
> ...


So if it's the same, you could probably go with either one. The down side of the RPC is that it has to be running BEFORE you want to run the crane. So it either runs all day to be ready but wastes energy, or every time you want to move the crane, you start the RPC, then wait a few seconds, then use the crane. The Phase Perfect is essentially instant, it's like a starter.


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## telsa (May 22, 2015)

JRaef said:


> From an eBay ad for the same crane:
> 
> 
> So if it's the same, you could probably go with either one. The down side of the RPC is that it has to be running BEFORE you want to run the crane. So it either runs all day to be ready but wastes energy, or every time you want to move the crane, you start the RPC, then wait a few seconds, then use the crane. The Phase Perfect is essentially instant, it's like a starter.


That's a new one on me: 480 VAC SINGLE PHASE Service power.

Live and learn, I guess.


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## telsa (May 22, 2015)

His insurance carrier is sure to be 'interested' in your improvisation.

This is the Internet.

It has its limitations.

Like -- I'm blinded.

BTW, do you have an E & O policy ?

I can't speak for every location -- but it's typical that any hoist in commercial service has to have an inspection and a permit.

This is not as high drama as an elevator -- but it's typical for the insurance firm to insist on the gadget being inspected and deemed suitable for the facility. 

No-one who really counts is at all impressed with what non-engineers can kludge up. ( The courts )

Take OFF the EE hat and put on your LLD robes. 

Legally, this is a no-win proposition for you. 

My own mother was in the insurance game.... claims coverage... not sales.

You would not _believe_ the ways that these gizmos fail. 

Then EVERYONE involved has the 'net' dropped on them.

I know straight off you're not carrying an insurance policy that will carry the load. [ You'd have to be paying for a 'rider' -- an extra -- and quite expensive it would be. ]

So, are you feeling lucky ? 'Cause when trouble comes -- you've bet all of your assets -- and citing this or that Internet forum -- heh -- the Court won't hear of it.

Trust me, no-one hauled through the 'liability system' EVER thought that that they'd be 'touched' in a million years. Yet, there they stand.

You realize that the actual fools that will be operating this hoist are CERTAIN to push it to its limits one fine day. That's the way people just are. There's no hoping otherwise. 

And, somehow, someone is sure to suggest that the power supplied to the hoist caused the calamity. 

If you think otherwise, then you're in for a real world legal education -- at a price you can't afford.

How many times have you seen hack work photos ? And the hackster's defense is "it works."

Heh.

Getting 'it' to work... may look great on paper... 'it' may actually function... and still be a 'time bomb' ... legally.

BTW, did you know that the NUMBER ONE reason for business bankruptcy was a court judgment ?

Yep. No fooling.


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## varmit (Apr 19, 2009)

Telsa covered the possible issues quite well. This would be a job to RUN from. Even if you were, foolishly, not concerned about liability, I would doubt that any crane company would certify this for use.


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## ByronDC10 (Jul 26, 2014)

Thanks for the thoughts. I think the best course of action at this point will be to see what it would cost to bring in 3-phase from the utility.. Probably be $20k or more but perhaps the only way to do it properly unless the crane manufacturer can suggest something that they would "approve."

The thoughts about liabilities and insurance are appreciated. I'm not a scab trying to rig this together as cheaply as possible. This Internet forum is just one small resource that I decided to get an opinion from, among many other sources that I will be seeking advice from, including manufacturers, inspectors, and perhaps my insurance provider.

-Byron


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## retiredsparktech (Mar 8, 2011)

telsa said:


> That's a new one on me: 480 VAC SINGLE PHASE Service power.
> 
> Live and learn, I guess.


It was available at one time from We Energies. It's now deemed obsolete, but they support existing installations.
I never knew it existed, seemed strange.


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## JRaef (Mar 23, 2009)

telsa said:


> That's a new one on me: 480 VAC SINGLE PHASE Service power.
> 
> Live and learn, I guess.


Huh? I think you misread something. 
Nothing in that spec days 480V single phase. The OP said he HAS single phase and his crane needs 3 phase, hence the phase converter. If he has 240V single phase, he can buy a transformer. 

But FYI, 480V single phase is somewhat common in far flung rural areas where the utility saves transmission cost and transformer size by running a single high voltage line out to a farm as a SWER service and give the farmer 480V single phase, from which he is responsible for any down stream transforming.


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