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is this correct?

wippin' boy

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Sep 14, 2005
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being of fairly simple mind and considering everyone draws these pictures there own way
i was ondering about this configuration

assuming high voltage side only and fusing of output ( t1,t2,t3)

and is the breaker or plug you plug into for L1 and L2 external of rpc control box sufficient for means of disconnect?

rpchivoltage.jpg
 
Looks right to me WB. :)

Except maybe potential relay. If it opened you have no feed to middle leg. Does it not open to take start cap out of circuit?

John Oder
 
Last edited:
Whippinboy

You are getting close with your sketch but there are still problems.

First: the potential relay doesnt' not need to be fed through the main contactor contacts. You can save these for something else.

Second: the potential relay has a coil and set of normally closed contacts and there is a common connection between them. The terminals are labled 1, 2 and 5 where 2 is the common connection between the coil and the contacts. Your diagram applies to RPCs of 5 hp or less. In this case you must connect PR terminal 2 to the generated phase, You sould connect terminal 5 to L3, then connect from terminal 1 to your start capacitor and from the start cap to L1. The internal PR wiring has the coil between termianals 5 and 2. the normally closed contacts are between terminals 1 and 2.

Third: All of the run caps and start caps should be before the thermal elements. I have built them with the start caps after the thermal elements and have operated these for many years without problems but I would never put the run caps after the thermal elements and now put all the caps before the thermal elements.

I posted a simplified drawing of a 7-1/2 hp RPC in a response to jminer99er yesterday. It is about two notes below your posting. This diagram shows a start contactor controlled by a potential relay which is necessary for anything larger than 5 hp. It shows how all the components are connected but not where the actual connections are made. Look it over and you can see the relationship of all the working parts. Please note that I put the start capacitor between L3 and the generated phase whereas you have it between L1 and the generated phase. Either method works--just realize my diagram is different.

I have 5 hp plans if you need them.
 
The blue wires are not tied into L1 and L2 on the far left.

The manufacured phase is not fed by L1 or L2 when running, it is manufactured by the idler motor.

If you do not switch the feed to the PR the start caps will be energized all the time and I do not think that would work.

All of the caps should be on the other side of the thermal overload.

-Joe
 
thanks guys
the relay spot was kindof a "metaphisical representation"
i did notice that joe's was "hooked across" the other phases
my pr should be here in the morning so i can have a look at what it's about
were gettin there
it's not just the building
it's understanding


so you can build one out of coconuts on a desert island if need be :D
 
ok
so i got my relay and it is as you describe
this is for a 5 hp converter

i know this seems like pulling teeth
but is this correct
it doesn't appear to me the same as joe's

2ndrpchighvoltage.jpg
 
Joe's instructions do no apply to the Steveco 90-66. He must have used something strange.

Potential relays are connected such that the coil is across one single phase line (after the main contactor) and the generated phase. Whenever the voltage here reaches the pickup voltage, the normally closed contacts open dropping the start cap from the circuit. The coil stays energized as long as the main contactor is energized.

I remember the potential relay having terminal two as the common connection. Please check your instructions and compare to your drawing. You seem to have #1 as the common connection.

The hookup is real simple once you see it. I will try to redline you drawing and repost.

Bruce Norton
 
Here is a redlined version of your drawing showing a Steveco 90-66 potential relay installed correctly. I forgot to erase the existing power factor correction capacitor when I added the red one.

Bruce Norton
 

Attachments

  • 3rdrpchighvoltage.jpg
    3rdrpchighvoltage.jpg
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well this is were we ended up
thanks to all concerned
voltages are actual taken during first run in 5 minutes and no smoke



rpc7-8aa.jpg


have not added power factor correction yet
was thinking 10 µf
any thoughts
 
10 mfd is about right for a first try on the power factor capacitor. I quit using them on the 5 hp models as I could get little improvement but give it a try any way. Be sure to make a table for documenting your capacitor values as you balance it. The values you have are typical of values I use for a 5 hp idler but i have encountered idlers that take more run capacitance. If you have not balanced it yet, just start with about half the caps connected, record, all three phase voltages and put a clamp-on amp meter on the generated leg. Be sure to follow Fitch Williams' technique for balancing. Try not to exceed 100% of the full load amps (FLA) rating in the generated leg. I like them about 90% but if the generated phase voltages get more than 10% above line you will have to settle for less.
 
Toolnut,

I know my diagram is not very clear to read, but it is for a Steveco Potential relay. I actually used two PRs and broke the start caps into 2 banks for my 10 HP converter rather than using the PR to control a separate contactor since it was cheaper to do the former in my case.

In my diagram, the PR coil is across L1 (black line) and the generated leg. (lower blue line) It switches the start caps which are connected to the other utility leg. All of the connections are after the main contactor.

-Joe
 








 
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