Power output of a RPC with 10 HP idler

If I have an RPC with a 10 HP idler, what is the maximum amount of power that I can draw from it, safely? I am interested in numbers for a resistive load and a motor. Resistive load could include some bad ass garage heater that could be much cheaper in 3 phase.

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Reply to
Ignoramus27279
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I would consider the idler to be good up to perhaps a 7-1/2 HP motor load. If you plan to plug reverse the motor, perhaps go down t a

5 HP motor load.

As for the resistor load -- you can re-wire the resistive heating elements to put all three on the same 240V single phase (if your breaker can handle that -- if it can't, it won't be able to handle the rotary converter driving that anyway.

Enjoy, DoN.

Reply to
DoN. Nichols

Thanks.

Well, the fan in the 3 phase heater may have a 3 phase motor...

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Reply to
Ignoramus27279

I used an RPC with a 10 HP idles that would start the 10 HP DC motors in my CNC lathes with the slow start function set real low. I now use an RPC with a 15 HP idler and it starts the 10 HP DC spindles with the slow start function set to the highest acceleration. BTW, this RPC will start any machine no matter how many other machines are running. The output from the RPC is wired into a separate panel. This panel has three phase breakers in it for each machine. And the mill with the

5 HP spindle has heaters in it for motor overload protection. ERS
Reply to
Eric R Snow

O.K. Run the *fan* from the RPC. The rest would be a lot more efficient run from single phase after rewiring. ("efficient" as in "cost you less to run".)

Enjoy, DoN.

Reply to
DoN. Nichols

Thanks. That's encouraging. I heard that extra 3 phase motors in the circuit only improve the 3rd leg -- as long as you can start them. Did you make that RPC or buy it?

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Reply to
Ignoramus27279

I bought this one. At the time, 8 or 9 years ago, I didn't know where to find the info that is so widely available today about building your own RPC. It is a good unit and has been trouble free except for a contactor that failed prematurely. It was the coil that failed, not the contacts. That was 7 years ago and the thing has been used at least 50 hours a week since I bought it. I have built two phase converters since, using info gleaned mainly from RCM, and both work very well. Eric

Reply to
Eric R Snow

Reply to
RoyJ

Thanks, that's very impressive!

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Reply to
Ignoramus27279

If the RPC is in the space being heated the efficiency isn't going to make any real difference in the cost of electricity. But it just doesn't seem right to run a phase converter to power a heater, does it?

Ned Simmons

Reply to
Ned Simmons

The first thing that came to my mind was three plastic buckets of brine and an ammeter.... One bucket for each phase to phase. The brine solution should be the same between buckets. Just sounded like a good idea, I'm no expert in that respect!

Reply to
carl mciver

there should also be enough surface contact, and also if the idler overloads due to too much current, it could burn up... the electicity that comes out of the wild leg, goes all the way through the idler.

Anyway, I experimented today and started a 7.5 HP motor. It started easily and the main idler did not even hiccup. That's my 200V 7.5 HP motor that I picked for $20.

I just had a thought, that if I start that 7.5 HP 3 phase motor after starting my phase converter, it will be a second idler in the system. With these two motors, started in sequence, I could conceivably run even larger pieces of equipment!

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Reply to
Ignoramus27279

What load was the 7.5 HP motor driving? IOW, how many horsepower was it actually developing?

R, Tom Q.

Reply to
Tom Quackenbush

There was no load, but I suppose that it did require a lot of juice for spinning up.

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Reply to
Ignoramus27279

Fuhgeddaboudit. Electric resistance heat is far and away the most inefficient way to heat a room. If you want to heat the garage you can rewire the elements in a 3Ph heater to run on single phase, but you are still going to eat it in the (posterior) big time when the electric bill arrives.

Buy a gas-fired or oil-fired unit heater, hang it from the rafters, punch a hole through the roof for the vent stack, and you are done.

Or get the long pipe style vented radiant heaters, hang one over the workbench and one in front of any machinery you will be working on for long periods. Again, note the word 'vented', you do not want to go offing yourself with Carbon Monoxide. And you want the appliance up off the floor, because gasoline fumes tend to pool down there.

If you have access to large quantities of used motor oil, you can build a Babbington Burner for an oil-fired heater, and run waste oil for your heat. Runs surprisingly clean.

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Reply to
Bruce L. Bergman

Bruce, can you educate me about these furnaces. How much do they cost and what's their size? I would rather not vent anything through the roof. I'll check their legality by calling our village zoning dept.

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Reply to
Ignoramus27279

Three incandescent lamps are good for this. Choose sizes that match the desired load. One HP = 746 watts. Relative brightness of each "phase" could be used for balancing - although most prefer a voltmeter.

Reply to
Robert Swinney

You will get a whole lot further with the Village's Powers That Be with a vented unit, trust me on this one. Unvented heaters are usually explicitly Verboten for residential use.

The Modine "Hot Dawg" Unit Heater is a low-profile unit that works in garages with only an 8'ceiling, without you banging your head into it - horizontal design hung off the ceiling or rafters, 1" clearance. And they say it's approved for residential use, meaning the PTB shouldn't have any complaints.

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24,000 to 60,000 BTUH Output, 27" wide, 22" deep, 13" or 18" high.

3" flue, and I'll bet it's a forced-draft burner since they say you can vent it horizontally through the wall.

Works just like a regular gas furnace, except no ducts. Just vanes to direct the hot air where you want.

And I have no idea about price, they play the "Call For Pricing" game. One website has the various sizes from $450 to $560, but as always a bit of shopping around can save a LOT.

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Reply to
Bruce L. Bergman

Be cautious with the Incandescent lamps - they run 10x current until hot !

That is short, but you are drawing 7000 watts or 10 HP -

Remember - when you flick on the lamp - that is when the bulb flashes and burns out. Most stressful time.

Go ahead, but keep it in mind. It might blow fuses.

Mart> Three incandescent lamps are good for this. Choose sizes that match the

Reply to
Martin H. Eastburn

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