Sharing a Rotary Phase Converter

[Little Bill]

A customer has a rotary phase converter (RPC) that runs only one machine. The RPC is connected directly to the machine via a SO cord. Now he has another machine and wants to run both machines off the RPC, but only one at a time. The two machines are very close in ampacity requirements. What would be the simplest, cheapest way to set up a way to switch from one machine to the other?
Do they make a 3-pole, double throw, switch? Maybe with a center off position?

 

[ptonsparky]

A customer has a rotary phase converter (RPC) that runs only one machine. The RPC is connected directly to the machine via a SO cord. Now he has another machine and wants to run both machines off the RPC, but only one at a time. The two machines are very close in ampacity requirements. What would be the simplest, cheapest way to set up a way to switch from one machine to the other?
Do they make a 3-pole, double throw, switch? Maybe with a center off position?

Yes, they do. In some cases it's called a transfer switch. Others use them to reverse mills ever month or so to get full use of the blades.

 

[ptonsparky]

Are they small enough just to feed a receptacle?

 

[MSU_Electrician]

A customer has a rotary phase converter (RPC) that runs only one machine. The RPC is connected directly to the machine via a SO cord. Now he has another machine and wants to run both machines off the RPC, but only one at a time. The two machines are very close in ampacity requirements. What would be the simplest, cheapest way to set up a way to switch from one machine to the other?
Do they make a 3-pole, double throw, switch? Maybe with a center off position?

I have hard wired them to a 125amp main lug with breakers for each machine.


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[Little Bill]

Are they small enough just to feed a receptacle?

A receptacle would most likely have to be a pin/sleeve type and would be expensive for two sets of them

 

[brantmacga]

Do they make a 3-pole, double throw, switch? Maybe with a center off position?

I had to buy a 60/3 double-throw switch earlier this year and it was $1k. Just FYI. And every manufacturer has had multiple price increases this year since I bought that.

 

[winnie]

Depending on the machines and the sizing of the RPC the system might work better with both machines operating but only one under load.

If the machines are large spinning loads such as saws, and the RPC not really properly sized for starting, then once one load is spinning it will act as an additional RPC for the other.

A panel with some form of interlocked breakers is probably the cheapest approach.

Jon

 

[ptonsparky]

IDR how you set it up.

Can you add DP contactor(s) and have a simple toggle switch select which one?

 

[retirede]

A receptacle would most likely have to be a pin/sleeve type and would be expensive for two sets of them

What HP are we talking about? Twist-locks might suffice.

And you don’t need two sets, just one receptacle and two plugs.

 

[oldsparky52]

A panel with some form of interlocked breakers is probably the cheapest approach.

Jon

I agree with this approach.

 

[electrofelon]

I wouldn't think twice about doing as MSU said and using a MLO and just having a breaker for each without any sort of interlock.

 

[Little Bill]

I found a 1-0-2, three position cam switch that I think will work.

 

[DrSparks]

IDR how you set it up.

Can you add DP contactor(s) and have a simple toggle switch select which one?

I like this solution. Contactors are cheap, just make sure they have adequate HP rating.

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