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Timer circuit for start capacitor contactor on a 600V RPC

TRC

Aluminum
Joined
Jun 22, 2022
I made a 600V RPC to power my 575V paper weight of a mill. It's struggling to start the mill motor when it's not in the mill (i.e. not connected to the transmission and the spindle).

Actually, I'm using a 0.25 hp motor to start the idler. I also need to keep this 0.25 motor running if I want to start the mechanically disconnected mill motor (my load motor). otherwise the whole RPC slow down and stop. Once the load motor is up to speed, I can stop the 0.25hp motor and every thing run correctly.

However, when I put the motor back in the mill, I can do the same to get the spindle rotate a bit, but the breaker jump before the mill get up to speed. After a some thinking, I came to the conclusion that I would need more power to start the mill. I think a few start capacitor would help. Which lead me here.

I need a starting circuit for the RPC. A standard Steveco potential relay won't do it since my circuit is 600V. I can find a bunch of 600V contactor, I just need a way to open the circuit after 1 or 2 sec to avoir damaging the start capacitor. I've looked a bit around, and there really isn't any magic box that do it for you at this voltage. Can anyone help with that?
 
You can swap the coil in your contactor for whatever voltage you like. You do not need 600V everywhere. I myself use 24Vac coils in a 240V RPC.
 
For the steveco type, you may be able to add a resistor in series with the coil..... it might also not work as desired. There are some alternate types that use an electronic circuit instead of the coil for sensing, and those could work, if the electronics can deal with the 600V

But the realproblem is that the Steveco (and the others) is not rated for 600 on the contacts, and the contacts are connected with the coil inside, so no separating them.

The "600V" contactor is the contact rating. Never seen a 600V contactor coil, but they probably exist..... no need in the US.
 
Wouldn't use a steveco if it was a freebie.
My method is a Allen-Bradley FSA3 delay timer and a 60A mercury relay with a 12v coil.


You don't have to do things just like all the internet articles. Wonder how many of those steveco guys rant and rave whenever a RPC guy buys one.
 
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Nice thing about a time-delay, is that if anything bogs the RPC, the start circuit will NOT come back on and pop the caps by staying connected too long.
 
You can swap the coil in your contactor for whatever voltage you like. You do not need 600V everywhere. I myself use 24Vac coils in a 240V RPC.
Sound like a great plan B.
How about a small step-down transformer and a 120v time delay relay?
I got this thing, I'll try to use a 2sec delay with a 120V contactor that will connect three 250V start cap in series.

But the realproblem is that the Steveco (and the others) is not rated for 600 on the contacts, and the contacts are connected with the coil inside, so no separating them.

The "600V" contactor is the contact rating. Never seen a 600V contactor coil, but they probably exist..... no need in the US.
I may go for something else then. I just need to make sure the start caps don't blow up with some sort of delay.
 








 
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