phase convertor voltage
#11
  
I am attempting to connect a "Phasemaster Rotary Phase Convertor". There are three leads, two of which I connected to the panel (50a, 240v). Out of the trhee, I found one which if connected (leaving one of the other two disconnected) doesn't work, so I think I can safly assume that is the phase being generated. It is. Problem is voltage form that lead to netrual/ground (as shown on my Fluke T5-1000 electrical tester) shows 256v. I'll be using this first to power a charge for a forklift and I woud prefer to not let the magic smoke out.

Any suggestions or comments will be helpful
Sign at N.E. Vocational School Cabinetmaking Shop 1976, "Free knowledge given daily... Bring your own container"
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#12
  Re: phase convertor voltage by MstrCarpenter (I am attempting to c...)
3 phase has a wild leg, and you found it. Make sure that leg is *not* connected to a switch connection to whatever you are hooking up/running with the convertor.
If it's a coil activated switch, it will fry the switch. Hook that wild leg to a motor connection.
Steve





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#13
  Re: phase convertor voltage by MstrCarpenter (I am attempting to c...)
Assuming it's a rotary phase converter, the 'motor' is a rotary transformer, and it's sort of smearing the magnetic fields across the unpowered winding, which in turn generates a current.  But the voltage, and even the phase angle, is not going to match the line voltage and phase angle perfectly, especially when unloaded.  Putting a load on it will pull the voltage down.  Maybe too much.  So you can't make any determinations on voltage until you put a load on it.  Run a motor under load and see what it is.  Sometimes capacitors are added to bring them all into better alignment, especially in phase angle.

Oh, and don't put any relay coils (controls) or other single-phase loads on that fabricated phase pole.
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#14
  Re: phase convertor voltage by MstrCarpenter (I am attempting to c...)
Thanks for the quick reply Steve. Before I saw your post I had already wired up another 3 phase motor that I use for a phase convertor in my shop. The "wild leg" was showing 176v, but I new it worked fine on equipment in my shop so I turned on the charger and it was putting out the required 36vdc. I hadn't opened up the charger to see which leg controlled the contactor, but it works. The charger doesn't have a neutral so I guess I had 66% chance of cooking the coil without checking first.

Tom, thanks for your explanation. It is a rotary, with a bank of caps. I was expecting the generated phase to fluctuate higher and lower than my input voltage, but when I read 256v I was thinking that it might have been wired for some special application. Is 256v too high? And will that affect the output of the charger? Currently it's drawing 13a on the 5hp slave motor generated leg, and 18 amps on the other two.

Woodnet is great!
Sign at N.E. Vocational School Cabinetmaking Shop 1976, "Free knowledge given daily... Bring your own container"
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#15
  Re: RE: phase convertor voltage by MstrCarpenter (Thanks for the quick...)
(06-28-2019, 06:25 PM)MstrCarpenter Wrote: Tom, thanks for your explanation. It is a rotary, with a bank of caps. I was expecting the generated phase to fluctuate higher and lower than my input voltage, but when I read 256v I was thinking that it might have been wired for some special application. Is 256v too high? And will that affect the output of the charger? Currently it's drawing 13a on the 5hp slave motor generated leg, and 18 amps on the other two.

Woodnet is great!

256V is almost 7% over 240V, where the utility is supposed to supply +5% to -10% of nominal, which is 240V.  So not terribly high.  

How did you measure the voltage? Phase-to-phase, or phase-to-ground? For the most part, phase-to-phase is all that matters.

Have you considered trying another 3-phase motor in parallel with the rotary transformer function motor?  It might smooth things out a bit more.  You could also mess with the capacitance, but that’s going to take some effort.
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#16
  Re: phase convertor voltage by MstrCarpenter (I am attempting to c...)
What brand RPC?
The run caps in it will adjust the voltage on the generated leg.
Contact your vendor in order to balance the RPC.
Id know the requirements of the charger from its mfg before calling the rpc vendor.


Glad its my shop I am responsible for - I only have to make me happy.

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#17
  Re: RE: phase convertor voltage by TDKPE ([quote='MstrCarpente...)
(06-30-2019, 11:34 AM)TDKPE Wrote: 256V is almost 7% over 240V, where the utility is supposed to supply +5% to -10% of nominal, which is 240V.  So not terribly high.  

How did you measure the voltage?  Phase-to-phase, or phase-to-ground?  For the most part, phase-to-phase is all that matters.

Have you considered trying another 3-phase motor in parallel with the rotary transformer function motor?  It might smooth things out a bit more.  You could also mess with the capacitance, but that’s going to take some effort.

Do like Tom said and check the voltage phase to phase while under load.   Then go from there .   Roly
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#18
  Re: phase convertor voltage by MstrCarpenter (I am attempting to c...)
Roly, I was apprehensive because I measured 256v between my "wild" or generated leg and netrual. The intended use of the convertor is to run concrete saws and grinders off residential power.
Sign at N.E. Vocational School Cabinetmaking Shop 1976, "Free knowledge given daily... Bring your own container"
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#19
  Re: phase convertor voltage by MstrCarpenter (I am attempting to c...)
Neutral?  What’s a neutral doing in there?   Confused
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#20
  Re: phase convertor voltage by MstrCarpenter (I am attempting to c...)
(07-06-2019, 04:02 PM)TDKPE Wrote: Neutral?  What’s a neutral doing in there?   Confused

The panel I was working with has one bar for both ground and neutral; all the green, white and bare copper wires terminate on it. My 10/3 SO cable is connected to a dbl. pole 30a breaker and that ground/neutral bar. I know I don't need ground or neutral to generate the third phase.
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