10HP Crane S Phase supply

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augie47

augie47

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State Electrical Inspector (Retired)
For you guys with equipment conversion experience..
E/C has a customer in an old facility with a 3 phase Oh O&H Crane.
The original service is long gone and a new 400 amp single phase 240/120 service was recently installed.
Now the customer wants to put the old Crane in service.
Largest motor is 10HP
Motor nameplates show 460/230 motors but from what little info was provided it looks like it was originally operated on 460.
POCO estimates cost for a new 460 service at $3 k
Best Route:
(a) Get 3 phase 480 service.
(b)Rotary Phase Converter
(c) Drive
(d) other ?
(e) run away
If he chooses (b)or (c) can either be obtained with 230 SP in and 460 3 phase out ?
 
Re b and c:
b. I have never seen dual voltage rotary converters.
c. The drive would have to use a voltage doubler rather than a straight full wave rectifier to get the DC needed. Probably better to add a step up transformer.
For overall performance, I would go for the new service.
I am not sure how adding a VFD would affect the control and operation of the crane. Well out of my area of expertise and scary dangerous.
 
Are the crane controls just on-off?

If so, how about new motors? I've never seen a 10hp, 230V, 1ph motor - but I suspect they are available. Big However: 1ph motors may well be a significantly larger frame and may not fit.

ice
 
GoldDigger said:
Re b and c:
b. I have never seen dual voltage rotary converters.
c. The drive would have to use a voltage doubler rather than a straight full wave rectifier to get the DC needed. Probably better to add a step up transformer.
For overall performance, I would go for the new service.
I am not sure how adding a VFD would affect the control and operation of the crane. Well out of my area of expertise and scary dangerous.
Click to expand...

VFD means Variable Frequency Drive.
Are you contemplating changing from a DC system to an AC system? Including replacing the motor?
 
Clarification:
Largest motor to be used at one time is the 10HP 3 phase P&H Crane lift motor.
E/C only bothered to forward motor nameplate which showed a dual voltage motor.
Abandoned safety switches etc. indicate the Crane was originally operated on 480v and I am unsure if the Crane is convertible to 230v although that may be possible (original control panel has nameplate missing..E/C did not check control transformer or components. DUH!)
Basic question is what options are available, if any, to use the existing 400 amp 240v 1 phase service to operate the crane ?
 
iceworm said:
"DC" ?

ice
Click to expand...
Yes. A VFD rectifies the input AC to power the internal DC bus. That DC is then used to provide pulses to the motor windings to simulate the variable voltage and frequency "AC" which goes to the motor.
To do this, the DC bus voltage needs to be comparable to the peak voltage of the nominal motor input.
A 240V input to a full wave rectifier will not produce a high enough DC bus voltage for a "480V" output.
 
The options that I can think of are:
single phase step up transformer followed by a rotary phase converter
rotary phase converter followed by a three phase step up transformer
solid state phase converter followed by a three phase step up transformer
480V three phase genset
motor/generator set
voltage doubling rectifier followed by VFD(s) with DC input

Thoughts:
Using separate VFDs for the various motors would be a way to enhance control of the crane.
The old motors will probably not be happy being driven directly by VFD.
Using a single VFD to generate 3 phase, with all of the controls _between_ the VFD and the motors will likely be hard on the VFD. But there are 'solid state phase converters' designed for this sort of application.
Getting a Genset might also allow facility backup.

While looking something up for this reply, I found that 'phase technologies' makes VFDs that take 240V single phase in, provide 480V three phase out, and claim near sinusoidal output. I have no experience with this company and don't know if this is snake oil. http://www.phasetechnologies.com/lowharmonicvfds/

-Jon
 
iceworm said:
Are the crane controls just on-off?

If so, how about new motors? I've never seen a 10hp, 230V, 1ph motor - but I suspect they are available. Big However: 1ph motors may well be a significantly larger frame and may not fit.

ice
Click to expand...

We have a brand new 10HP Baldor sitting on our shop floor that was removed from a job. The equipment dealer that sold it to a customer didn't realize he needed a 480v 3 phase motor when he dropped off the equipment to be wired, so we swapped it out for the right one.

These 10HP single phase motors are weird though, we tried to get the motor shop to trade us straight across for the new 480 3 phase one, but he said the last one he had on his shelf took better than 2 years to sell.
 
Is the only thing that would use 480V the motor? If that's turns out to be true and since it is dual rated, a rotary phase converter would work better than a VFD.

By the time you cover the cost of the converter and install, resizing any conductors and equipment necessary, and monkeying around making sure everything works, and fixing and replacing anything that goes wrong..... $3000 for the new service is likely to come in as the lower cost option.
 
ActionDave said:
Is the only thing that would use 480V the motor? If that's turns out to be true and since it is dual rated, a rotary phase converter would work better than a VFD.

By the time you cover the cost of the converter and install, resizing any conductors and equipment necessary, and monkeying around making sure everything works, and fixing and replacing anything that goes wrong..... $3000 for the new service is likely to come in as the lower cost option.
Click to expand...

I second that. All the ideas sound workable but the cost associated with them is not even close to $3k. The service upgrade is by far the best option.
 
$3K to get 480 volt service to the place is a steal and most other options will cost just as much if not more and some will have limitations though they can be overcome by throwing more money at the installation.

If the motor is a NEMA standard frame, general purpose motor - replace with a single phase motor. 10 HP single phase may be uncommon to some, but I see them all the time so they are not "non existent". Baldor even makes 16 HP single phase motor that is fairly common around here on crop storage aeration fans. That is the largest standard frame size general purpose type motor I can recall ever seeing, if they need a larger fan then that can drive they have to go with three phase motor.
 
kwired said:
$3K to get 480 volt service to the place is a steal and most other options will cost just as much if not more and some will have limitations though they can be overcome by throwing more money at the installation.

If the motor is a NEMA standard frame, general purpose motor - replace with a single phase motor. 10 HP single phase may be uncommon to some, but I see them all the time so they are not "non existent". Baldor even makes 16 HP single phase motor that is fairly common around here on crop storage aeration fans. That is the largest standard frame size general purpose type motor I can recall ever seeing, if they need a larger fan then that can drive they have to go with three phase motor.
Click to expand...
I must be missing something here.
Why would you use a single phase motor if three phase is available?
 
There is no free lunch here, all options will cost you money so it's going to be a cost / benefit analysis.

Another option by the way, get a 1 phase 240-480 transformer just big enough for the crane only, then get 480V VFDs that can accept single phase input (some cannot, so be careful). Then you can leave everything else the same as it is now, except you will be replacing the crane starters with the VFDs.

However...

While I too think this may cost more than just getting the new service then on top of that, applying a VFD to a hoist motor is also not for the novice. It takes some specialized application experience and will likely mean the most expensive type of VFD, one capable of Flux Vector Control and with Torque Proving capability, plus you will need to add a shaft encoder to the motor. The bridge and trolley travel motors will be fine with simpler VFDs, its just the hoist that becomes problematic and can be dangerous if done wrong. I would not hesitate for a moment to go this route because having VFDs on crane systems makes them much easier to use, but I have nearly 30 years experience with VFDs. The only caveat to this is if your hoist by chance uses a self-locking high ratio worm drive, so that when the motor stops, the shaft cannot move under load. Those exist, but unless you are a hoist expert, you would need to hire one to be sure, so more $$$.

The thing I don't like about RPCs on cranes is that they are not "instant on" unless the RPC is just sitting there running all day waiting for you to call for a crane, which is very wasteful. So that might be OK as long as you know that when you want to use the crane, you have to fire up the RPC first, THEN start using the crane. And here again, you will have to either boost the voltage to 480V downstream of the RPC with a transformer, or double the size of the wiring and replace all of the motor starters for the crane equipment if you rewire all the motors for 230V.

My opinion then is to just leave it as is and get the 3 phase service brought in, $3k is dirt cheap. The PoCo must have the transformers on the pole already. That may not be your only cost of course, because if you already have wiring installed for a 120/240 single phase service, you will have to now add a single phase transformer to feed that from your 480 service (or have two service drops). Still probably the least expensive and simplest route.
 
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Besoeker said:
I must be missing something here.
Why would you use a single phase motor if three phase is available?
Click to expand...
It's not available. He currently has a single phase service. Replacing the motors with single phase motors is an option he has, in lieu of changing to a 3 phase service. However, it would also entail changing out the entire crane control system as well, which I think is also ultimately going to cost more than the new 3 phase service drop.
 
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Besoeker said:
This from post #6:

What am I missing?
Click to expand...
You are not missing anything. Some time after the crane was taken out of service (building use changed?) the three phase service that supplied it was also removed or abandoned.
That seems to be what the OP implied.
Now possibly the original installation also used an RPC which was scrapped or sold off?
The low POCO fee for providing three phase 400V suggests that they will be reusing the pots that supplied the earlier service and have been sitting idle.
 
kwired said:
.........10 HP single phase may be uncommon to some, but I see them all the time so they are not "non existent". Baldor even makes 16 HP single phase motor that is fairly common around here on crop storage aeration fans. That is the largest standard frame size general purpose type motor I can recall ever seeing, if they need a larger fan then that can drive they have to go with three phase motor.
Click to expand...
10HP single phase is not usual for me either, but this is the first time I have ever heard of a 16HP. I believe you that they exist but I always thought ten was the largest.
 
GoldDigger said:
You are not missing anything. Some time after the crane was taken out of service (building use changed?) the three phase service that supplied it was also removed or abandoned.
That seems to be what the OP implied.
Now possibly the original installation also used an RPC which was scrapped or sold off?
The low POCO fee for providing three phase 400V suggests that they will be reusing the pots that supplied the earlier service and have been sitting idle.
Click to expand...

exactly !

I find new technology often leaves me behind and i was and the E/C is in the dark. I was attempting to assist him by looking for an option I had not considered.
Upfront it appears reactivation of the 3 phase service is the best answer.
Thanks, guys.
 
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