# Rotary phase converter connected motor issue



## kevink1955 (Apr 25, 2012)

Whoever messed with it first may have damaged the pump motor.

I would rent a 3 phase gen set and see if the pump runs first before trying anything else.


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## 8V71 (Dec 23, 2011)

It sounds like the pump motor may be mechanically locked up. I didn't do the math but a buck boost only has to be sized for the buck/boost, 37 volts in your case as part of the VA calculation.


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## wendon (Sep 27, 2010)

Does the pump motor have a starter? If it does, make sure that the control wiring is connected to L1 and L2. Do not connect any control wiring to the manufactured phase.


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## JRaef (Mar 23, 2009)

wendon said:


> Does the pump motor have a starter? If it does, make sure that the control wiring is connected to L1 and L2. Do not connect any control wiring to the manufactured phase.


Bingo! First order of business. 

Also, make sure whoever messed with that pump didn't accidentally connect it for High voltage (460V). It would start, it would just have no torque and trip out once it started moving water.


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## GEORGE D (Apr 2, 2009)

wendon said:


> Does the pump motor have a starter? If it does, make sure that the control wiring is connected to L1 and L2. Do not connect any control wiring to the manufactured phase.


Yes it does. I will check that first when I arrive there. Glad I asked, I don't think that would of crossed my mind!


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## GEORGE D (Apr 2, 2009)

8V71 said:


> It sounds like the pump motor may be mechanically locked up. I didn't do the math but a buck boost only has to be sized for the buck/boost, 37 volts in your case as part of the VA calculation.


That's was my thought as well. The fact it merged good and that it would run, or try to, for a few seconds lead me to believe it was bound up. As for BB, wouldn't the entire load travel through it? I don't have diagram handy.


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## 8V71 (Dec 23, 2011)

GEORGE D said:


> That's was my thought as well. The fact it merged good and that it would run, or try to, for a few seconds lead me to believe it was bound up. As for BB, wouldn't the entire load travel through it? I don't have diagram handy.


In your first post you said _"The pump motor never even turned"_. Here you are saying it tried to run for a few seconds. Important info to be clear for troubleshooting. If the pump is actually turning for a few seconds I would look into *wendons* suggestion. I also thought this was a working installation that failed but after reading the OP again it seems more like a new installation that has never worked.

The entire load does travel through the BB, and they take that into consideration, but it is only changing the voltage within itself, like 32 volts times current. Sort of like selecting the wattage of a series resistor. The lower the resistance (or voltage change), the lower the wattage has to be.


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## GEORGE D (Apr 2, 2009)

8V71 said:


> In your first post you said "The pump motor never even turned". Here you are saying it tried to run for a few seconds. Important info to be clear for troubleshooting. If the pump is actually turning for a few seconds I would look into wendons suggestion. I also thought this was a working installation that failed but after reading the OP again it seems more like a new installation that has never been working. The entire load does travel through the BB, and they take that into consideration, but it is only changing the voltage within itself, like 32 volts. Sort of like selecting the wattage of a series resistor. The lower the resistance, the lower the wattage has to be.


Correct, the pump motor never turned. What I meant by trying to run is that the starter remained closed for a few seconds prior to tripping. To me that seemed to be more of a mechanical problem rather than a short circuit or grnd fault which would/should trip instant and ahead of starter. As for BB, that makes sense what your saying, it just seems wrong tying a 50+ amp circuit into those tiny lead wires! but then again, it seems all transformers have small wires within.


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## 8V71 (Dec 23, 2011)

How difficult would it be to check if the pump motor turns free by hand?


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## GEORGE D (Apr 2, 2009)

8V71 said:


> How difficult would it be to check if the pump motor turns free by hand?


Impossible. Is part of an assembly, hidden within a large tube style cylinder. I didn't even want to attempt to open it possibly damaging some type of seal and then owning it.


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## Jlarson (Jun 28, 2009)

Get phase-phase voltage readings as it starts. Logging or min/max meter if possible. 

What is the service situation, how far from the panel, size of feeders?


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## GEORGE D (Apr 2, 2009)

Jlarson said:


> Get phase-phase voltage readings as it starts. Logging or min/max meter if possible.
> 
> What is the service situation, how far from the panel, size of feeders?


Feeder is less than 50' from idler motor and is #6's which I believe may be undersized according to manufacturer. I do know the idler motor was drawing around 25 amps on each leg while running.


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## micromind (Aug 11, 2007)

A couple of thoughts here;

1) If this is a basic submersible pump (like a well pump), the motor will not like receiving its power from a phase converter. These are pretty 'high strung' motors and they have very little tolerance for voltage imbalance. I'd also megger the motor. 

2) Depending of what type of pump it is, it might not start in reverse. Try swapping two of the motor leads and see if it'll start in the opposite direction. 

3) Check the capacitors in the phase converter. There are usually a bunch of them in parallel, if one or more has become disconnected, the no-load voltage will be ok, but not ok under load. Test them for actual µfd vs. nameplate. 

4) The B/Bs will seem grossly undersized. The load current goes through the secondary, not the primary. They usually come with either 12/24 or 16/32 secondaries. As a general rule, if the secondary current is more than the load, they'll be ok. 

In your case (10HP motor at 208 volts; likely around 26 - 30 amps)
500/32=15.6 amps; too small
500/24=20.8 amps; too small
500/16=31.25 amps; ok
500/12=41.7 amps;ok. 

Depending on the transformers supplied, you can buck off either 12 or 16 volts, but not 24 or 32. 

Use only two B/Bs, if 3 are connected in a closed ∆, they will try to balance voltage, but due to their small size, they cannot. So at least one of them (more likely two) will burn up.

P.S. #6s are too small. The rated single phase current to the converter will be around 100 amps. The actual current with a 10HP load will be more like 50 or less.


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## GEORGE D (Apr 2, 2009)

Ok went back out there today with fountain rep and here's what I happened-

He pulled it out of water, dismantled it and decoupled the motor from pump and motor worked. We spun the impeller by hand and it spun but not smoothly (not sure if that's normal). So we put back together and bump it and sure enough it worked. Finally get it out into water and now it would start pumping water but cut out about 2 seconds into it. The control panel has an integrated phase monitor device that was doing the cutting out. I'm not sure of the % tolerance it has as far as imbalance goes but obviously enough to trip it every time. I tried measuring the voltage phase to phase while running but was getting unreliable readings, which by the way, has me a bit frustrated with my Fluke 289, I used the Max/Min and would get a max of around 20 VAC, but would get around 225ish sluggishly when trying to manually read voltage. Is there a quick feature on that meter, to basically show real time readings instead of that awful delay? Surely the meters a nice instrument, I just haven't gotten used to it. Sorry to side track, basically the verdict I suggested was to possibly look into a VFD as a solution. This way we get the our 3 phase and also soft start capabilities. Am I on the right track? If so, you generally double the size of the VFD to compensate the phase loss....right? Any help is appreciated, as always.


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## Noble 32 (Feb 25, 2013)

GEORGE D said:


> * We spun the impeller by hand and it spun but not smoothly (not sure if that's normal)..[/*quote]
> 
> I know i am not the best there is but i see this alot in my plant. Usually a sign of a bad bearing/warped shaft which will throw the ols on a motor in a heart beat. This is where i would look first if it was on the floor


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## micromind (Aug 11, 2007)

If the control panel has a phase failure relay, and it's being fed by a phase converter, it will almost always trip under load. These relays are usually set at about 4% imbalance; a phase converter will almost always be more than that when its loaded. 

Given that this is a submersible pump motor, I wouldn't run it on a phase converter at all. These motors are not very tolerant of anything other than reasonably balanced sine-wave power. 

A VFD may very well be the best choice here. Yes, you'll need to double the VFD HP for single phase input, and be sure that the VFD will accept single phase. Most will, some won't. 

Also, stay away from the cheap VFDs like you find on ebay. Generally speaking, with VFDs (and a lot of other equipment) you get what you pay for.

This won't be cheap, but it'll solve a lot of problems. 

As far as soft-starting, a lot of VFDs can be programmed to ramp from zero to full speed anywhere from a fraction of a second to over an hour. Same thing with soft-stopping. 

VFDs produce heat when they run, make sure to ventilate it properly.


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## GEORGE D (Apr 2, 2009)

micromind said:


> If the control panel has a phase failure relay, and it's being fed by a phase converter, it will almost always trip under load. These relays are usually set at about 4% imbalance; a phase converter will almost always be more than that when its loaded.
> 
> Given that this is a submersible pump motor, I wouldn't run it on a phase converter at all. These motors are not very tolerant of anything other than reasonably balanced sine-wave power.
> 
> ...


Great, thanks micro, I'll have to start sourcing & pricing that setup. Any recommendations for a lower end vfd that's suitable?


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## JRaef (Mar 23, 2009)

A few of words of caution here. 

1) Often, submersible pump mfrs will dictate a maximum acceleration time. This is because the pump bearings are dependent upon the water pressure as a lube and without it, the pump fries very fast. It will have a thrust bearing that lets it start, but within 2 seconds or so the pump must be at full speed or the damage starts. That shouldn't be a problem for the VFD to accomplish, but it just means you cannot leave them on the factory default settings.

2) Technically any VFD is capable of being run on single phase with proper de-rating, but what micromind is referring to is that some designers never anticipated doing that on larger drives and they didn't make the Phase Loss protection capable of being turned off. So to tell in advance, look at the manual BEFORE you buy it and make sure there is a parameter assigned to disabling the Phase Loss protection. If there isn't one, you will not be able to use that drive.

3) Some submersible pumps require Class 5 overload protection or you void the warranty (Franklin), most VFDs provide Class 10 and many are not adjustable. Double check that with the pump mfr. Frsanklin requires you to use their Subtrol unit to get the warranty, and I'm not sure if they are rated for use with a VFD or not, Franklin makes their own VFDs and are known to force people to only use their stuff.


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## GEORGE D (Apr 2, 2009)

JRaef said:


> A few of words of caution here.
> 
> 1) Often, submersible pump mfrs will dictate a maximum acceleration time. This is because the pump bearings are dependent upon the water pressure as a lube and without it, the pump fries very fast. It will have a thrust bearing that lets it start, but within 2 seconds or so the pump must be at full speed or the damage starts. That shouldn't be a problem for the VFD to accomplish, but it just means you cannot leave them on the factory default settings.
> 
> ...


Good advice, this is a Franklin motor. I guess I can contact them first and see about getting vfd from them. Also, as micro mentioned, this will be outside, do you think a heating unit is absolutely necessary? If so, would it still be necessary if it ran 24/7?


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## wendon (Sep 27, 2010)

GEORGE D said:


> Good advice, this is a Franklin motor. I guess I can contact them first and see about getting vfd from them. Also, as micro mentioned, this will be outside, do you think a heating unit is absolutely necessary? If so, would it still be necessary if it ran 24/7?


Are you talking about a heating unit or a cooling fan? If you use the outdoor enclosure from Hoffman designed for VFD's, it comes with fans installed. It has a thermostat that cycles the fans. I wouldn't think you would need a heater down there in the tropics! We do need them up here on the frozen tundra though. -22F this morning with a breeze!! You might want to check and see if the motor is VFD rated too. If it's going to be used a lot, I'd make sure, like has already been stated, to use a quality brand.


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## GEORGE D (Apr 2, 2009)

Well the fountain rep called around today and spoke with the converter manufacturer who's telling him that it sounds like all he needs is to add a few more starting capacitors. This should get motor up to speed and help balance voltage to prevent phase monitor from dropping out. I advised the rep that this didn't sound promising and that we should still look into a VFD solution. Thoughts? I plan on calling Franklin tomorrow and see what they say.


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## micromind (Aug 11, 2007)

Adding more capacitors to the phase converter will help with voltage balance, to some degree at least. Especially with a constant load. 

The extra caps might need to be brought in when the pump motor starts, it's possible that if they are in the circuit with no load, the system could become capacitive instead of inductive. This results in unstable voltage, and is pretty rough on the idler motor. 

A 2 or 3% voltage imbalance with a true sine wave will be easier on the pump motor than a closely balanced but distorted wave from a VFD.


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## Jlarson (Jun 28, 2009)

One of my rules, fountain/aerator reps are good for one thing, paddling the boat out to get the thing, their electrical advice is useless. :laughing:

If it is a Franklin motor, here is a page from their AIM on VFD use.

http://www.franklin-electric.com/media/documents/60Hz_AIM_40-41.pdf


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## GEORGE D (Apr 2, 2009)

Jlarson said:


> One of my rules, fountain/aerator reps are good for one thing, paddling the boat out to get the thing, their electrical advice is useless. :laughing:
> 
> If it is a Franklin motor, here is a page from their AIM on VFD use.
> 
> http://www.franklin-electric.com/media/documents/60Hz_AIM_40-41.pdf


Thanks man, wow, what a PITA to install a vfd here. I guess it's definitely worth trying out the capacitors first. I really don't want to go down the drive road now. Btw, this all started because the property owners ordered 3 phase, not realizing they only had single phase. Being a custom build, returns are not accepted.


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