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Potential relay wiring.

Don Gitzel

Aluminum
Joined
Jul 25, 2017
I am trying to wire a potential relay into my rotary Phase Converter for remote starting. I am not having success. Here is the wiring diagram that I found on the web. Any ideas. 4DDA9652-8E10-4B2C-964D-F20F1CFBC157.jpg
 
Try uploading a pic thats readale if zoomed, and preferrably the correct way.
Any ways, the simple way the relay will have a Normally open contact 11/14 or similar marked.
That where you connect the wires going from it's source(11) and the wire to the start (14).

A1 /A2 you suplly with your reference potential to A2, and you take the + to the coil through the switch and into A1 to start it.

That's a completely basic way to do it, be sure to have the correct voltage and current capacity through the relay.
 
All of the potential relays I have seen have seen are for single phase hard start applications have normally closed contacts. The emf generated by the start winding fires the relay associated with the n/c contacts dropping out the start capacitance. Trouble is I cannot get the common connection of the three phase motor generating the third phase. Potential relays are marked 5-2-1. (Can she run—-common,start,run). There must be a way cause commercially manufactured rotary Phase Converter’s use potential relays.
 
The diagram you show is one that is out on the web, a standard setup.

Are you doing differently as far as remote start?

Are you sure you are wiring as it shows?

What are your voltages?

What voltage is the relay set for?

If you are wiring it in for "remote start", how was it wired before that did not need that?

The diagram should work. 2 and 5 are the coil, the NC switch is between 1 and 2. As the motor comes up to speed and the back EMF rises, at some point the relay is pulled-in, disconnecting the start capacitor.

If your setup is not working, the coil may not be wired across the correct points. I am assuming from what you wrote that the relay is performing the start, but is not pulling in, That may be due to a wrong connection, but is may also be due to a voltage setpoint that is too high, so that the pull-in voltage is never reached.

Some relays are all electronic, and require component changes to adjust voltage. Older mechanical ones may have a screw type adjustment to set voltage. You should see if your mains voltage is sufficient to cause the relay to pull in and open the circuit. Back EMF will be lower than mains voltage, so the relay needs a set point that is sufficiently lower to guarantee it will release the capacitor circuit at 70% or 80% of mains voltage as a back EMF. That should indicate sufficient speed for the motor to to pull-in to normal speed without more help.
 
Your reply to my problem encourages me to not give up on on this venture. I have been wiring my converters so that the relay that brings in the start capacitor stays energized as long I have the start button pushed in. As soon as the idler comes up to speed the button is released and the start capacitance drops out. Simple. No need for a potential relay. This converter will be started remotely and needs a means to disconnect the start capacitance. If I can’t get the potential relay wired I may use timers. Thanks for your help.
 
I checked the wiring and tried to start the converter again. It started and then growled ferociously. I quickly pulled off the wire from the coil of the starting relay. The converter settled down and ran smoothly. I then reattached the wire to the coil and the converter continued to run smoothly. I think I will find a time delay relay instead of the potential relay.
 
Sounds like a problem with the voltage, or at least as if the relay is not pulling in and releasing. Might be voltage, or might be that the relay is welded. Running a contactor it should not be welded shut, so maybe the voltage is not appropriate. The exat part number should indicate the voltage range. If too high, it will never pull in and will keep the start capacitors in-circuit. That can cause the growling.
 
Found a better version of the diagram in the first post.
RotaryPhasePotentialRelay.jpg
I checked the wiring and tried to start the converter again. It started and then growled ferociously. I quickly pulled off the wire from the coil of the starting relay. The converter settled down and ran smoothly. I then reattached the wire to the coil and the converter continued to run smoothly.

If the starting relay you pulled the wire off is labeled power contactor in the diagram, this indicates that there is not enough voltage to energize the potential relay while the start capacitors are in circuit, but there is once the they are out. So when you disconnected the wire, the potential relay pulled in, and disconnected the start capacitors in such a way that they were still disconnected when you reconnected the wire.

This indicates that the potential relay is good, and is wired correctly. Just needs to be adjusted to energize at a lower voltage, or a lower voltage one installed instead.
 
RustySparks. I think you have diagnosed the problem accurately. The only relay I was able to find was labeled “universal” but obviously does not work for me. What do you think about using a timer to disconnect the start capacitance?
 
I have used timers for a few things, I like them. But then I also make microcontroller controlled things and write programs for them in C. If I was doing this, a potential relay would be the way I would do it. More elegant engineering solution. Try making a quick AC voltage measurement across the potential relay coil while the growling is going on. See if you can find a potential relay rated for the voltage you get. An adjustable one would be best.
 








 
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