# Rotary Phase Converter



## dronai (Apr 11, 2011)

The well has a 25 hp pump. It has its own starter, but the pump is three phase, from a single phase source.

Am I right in this sequence ? I would need to go from:

The float switch to an icecube relay, to get the RPC up and running, to a time delay.

From the time delay, back to the starter terminals, where the float wire originally was landed.

Is this sequence correct ?

*I don't have anything to draw a schematic except "Paint".


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## Wirenuting (Sep 12, 2010)

dronai said:


> The well has a 25 hp pump. It has its own starter, but the pump is three phase, from a single phase source.
> 
> Am I right in this sequence ? I would need to go from:
> 
> ...


Don't know if this helps. 
A Square D wiring book. 

http://ecatalog.squared.com/pubs/Machine Control/0140CT9201.pdf


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## McClary’s Electrical (Feb 21, 2009)

dronai said:


> The well has a 25 hp pump. It has its own starter, but the pump is three phase, from a single phase source.
> 
> Am I right in this sequence ? I would need to go from:
> 
> ...


Generally when people ask if the control wiring is "right"...the give some type of description on what they want the system to do...


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## dronai (Apr 11, 2011)

mcclary's electrical said:


> Generally when people ask if the control wiring is "right"...the give some type of description on what they want the system to do...



The problem is, by using an RPC, it has to be running, before the pump can be started.

Since the pump is a large back-up seconary pump, it will rarely be used.

So there is no need to leave the RPC running.


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## Jlarson (Jun 28, 2009)

You need a starter to start the RPC. Float switch starts the RPC, and the timer, then the well starts.


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## JRaef (Mar 23, 2009)

Yes you want about 2-3 seconds between starting the RPC and starting the well pump motor. Sounds like you got it figured out. 

But you could also look for a timer that has both timed and instantaneous contacts. So wire the instantaneous contacts to energize the RPC starter, then jump to the timed contact to feed the pump starter. But if you already have these separate parts, that should work fine.


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## dronai (Apr 11, 2011)

JRaef said:


> Yes you want about 2-3 seconds between starting the RPC and starting the well pump motor. Sounds like you got it figured out.
> 
> But you could also look for a timer that has both timed and instantaneous contacts. So wire the instantaneous contacts to energize the RPC starter, then jump to the timed contact to feed the pump starter. But if you already have these separate parts, that should work fine.


Thanks, I will look for the timer you mentioned.


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## JRaef (Mar 23, 2009)

dronai said:


> Thanks, I will look for the timer you mentioned.


If you have trouble finding it, look at using an industrial machine tool relay with a separate time head.


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## Jlarson (Jun 28, 2009)

This is a crappy diagram of how I do it.

Sent from my Droid


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## dronai (Apr 11, 2011)

Well that's one way to get a drawing posted. Starter for RPC has terminals 1, and 3 so I can bypass it.

Here was my rough attempt to make a drawing.


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## Jlarson (Jun 28, 2009)

Yeah graph paper is quicker then CAD lol

Sent from my Droid


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## dronai (Apr 11, 2011)

Line Diagram Before adding TD, and after. Mechanically, I know how to do it, but drawing it, is this right ?


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## Jlarson (Jun 28, 2009)

Oh yeah I forgot the well has it's own starter already.


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## Mike in Canada (Jun 27, 2010)

Before you do this, check the coil voltage on both starters. Just in case.


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## Jlarson (Jun 28, 2009)

dronai said:


> Line Diagram Before adding TD, and after. Mechanically, I know how to do it, but drawing it, is this right ?












This one looks good, I prefer to do the controls in ladder just because it's more organized and easier to t-shoot from.










This one isn't gonna work. You've got pretty much everything in series and you've taken control power from both starters. 

Personally I like to feed all my controls from the single phase starter. You'd take my drawing and just tie the control ladder in to the line side of starter #1.


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## John Valdes (May 17, 2007)

I agree with Larson on the ladder drawing. That's how I was taught to do it. I cannot stand to troubleshoot any system with physical drawings.

They are cumbersome and designed for someone who does not understand how to read a schematic.


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## dronai (Apr 11, 2011)

John Valdes said:


> I agree with Larson on the ladder drawing. That's how I was taught to do it. I cannot stand to troubleshoot any system with physical drawings.
> 
> They are cumbersome and designed for someone who does not understand how to read a schematic.


I guess I have to practice using a ladder diagram. I see things more clearly with the other.

My main work is repetative, and usually doesn't require using any schematic drawings, except architecturals for building. Only encounter it when I get something mechanical, and interesting.


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## kowalekg (Jul 5, 2011)

dronia

Yes, as an overview you have the correct thought process. Just to breifly summarize the phase converter has to be running at full rpm, so as to generate proper output voltage before the pump motor is energized. 

The float switch would have been connected to the pump starter contactor coil. When the coil is energized the contactor closes and voltage is connected to the pump motor. Now adding the step of using an RPC for 3-phase voltage, the RPC must be "turned-on" by the float switch and be upto full speed before the pump motor is started. The time delay function for the RPC (electronic timer & power contactor) delays the output voltage from the RPC being connected to the starter contactor for the pump motor. A typical delay is a five second window. In that time frame the RPC Idler motor is upto full speed.

One other note, the ice-cube relay interface between the float switch and RPC start circuit s/b rated for min. of 240V and 2 amp rating.


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