Single Phase but 3-wires to motor
Single Phase but 3-wires to motor
(OP)
Looking for interpretation of the attached drawing. Power source is 2-wire, single phase. Wondering if the pump motor is 3-phase (hence the 3 wires going to the motor) using the capacitors for start and run phase shifting, or ??





RE: Single Phase but 3-wires to motor
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RE: Single Phase but 3-wires to motor
RE: Single Phase but 3-wires to motor
RE: Single Phase but 3-wires to motor
RE: Single Phase but 3-wires to motor
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If we learn from our mistakes I'm getting a great education!
RE: Single Phase but 3-wires to motor
RE: Single Phase but 3-wires to motor
No three phase.
No phase conversion.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Single Phase but 3-wires to motor
Look at the diagram again more closely. Why would you have the resistor in a cap-start single phase motor with an external start circuit? It's not there on a centrifugal switch version is it? In some SPC designs, they use the resistor to cause a slight delay in the output of that starting cap which creates a phantom rotation to start the motor spinning.
The only thing about that diagram that bothers me is the R, W, B terminal numbers, which looks like Red, White and Black. That seems on the surface to indicate single phase. But that may just be some home-made concept because they planned on using SO cord for the connections and those are the colors you would find in something like 12-3 W/G cord, Black, Red, White and Green.
By the way, I had a brain fart and had to use the term "voltage relay" in my earlier post, I meant "potential relay".
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Single Phase but 3-wires to motor
RE: Single Phase but 3-wires to motor
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Single Phase but 3-wires to motor
RE: Single Phase but 3-wires to motor
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Single Phase but 3-wires to motor
RE: Single Phase but 3-wires to motor
The capcitors are labeled SC and RC, which might suggest stand for cap and run cap as I think was suggested.
But look at RC1 for example. It is connected (in series with relay coil) between terminals R and B. But R and B are connected to the input power. So we have RC1 and the relay in parallel with the input power. Does not seem like a run cap which should be in series with a motor winding. Maybe I'm missing something... someone can explain in more details what the heck that circuit is supposed to accomplish?
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(2B)+(2B)' ?
RE: Single Phase but 3-wires to motor
"The capcitors are labeled SC and RC, which might suggest stand for startcap and run cap as I think was suggested."
=====================================
(2B)+(2B)' ?
RE: Single Phase but 3-wires to motor
Look at the connection from the junction of the relay coil and RC1 which goes to motor terminal W. I am pretty sure that W is the start winding. It's a really goofy drawing, it could have been drawn a lot more clearly.
I withdraw my earlier remark about it being a current-sensing relay. I blame the goofy drawing affecting my eyes.
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Single Phase but 3-wires to motor
As I read the diagram W is the start winding.
The relay is across the start winding and operates when the back EMF comes up.
The run capacitor is in circuit with the start winding to increase the HP somewhat.
Motor capacitors are generally discharged through the motor winding. The resistor may be a discharge resistor (or not).
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Single Phase but 3-wires to motor
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(2B)+(2B)' ?