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Three Phase Question

I have a three phase one and a half HP Milling Machine, a three HP Lathe and a one HP Surface Grinder . I run them off a three HP Leeson Speedmaster Micro Series Compact Inverter that has an over load capacity of 180% for 30 seconds and a 150% for one minute. The installation electrician told me that he could only install one receptical, so I have to switch plugs every time I use a different machine. I never power more than one machine at a time. Is there a safe way to avoid changing the plug every time I change machines? Thanks .... Al Basham

Reply to
Al Basham
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You might consider hard-wiring the 3-phase machines with drop wiring from the overhead. I have done this in my shop with 3-phase as well as single phase machines.

Reply to
Robert Swinney

I think the issue is whether the inverter is ever on when there are no machines connected. Some inverters are specified for this, some will shut down as an overload, I've heard that some will fry. This is why machines are usually switched from the inverter, not from the machine.

It sounds like you already have that situation if the inverter is wired to the machine via a plug. So either your inverter can deal with an open circuit, or you are already taking care of power sequencing. Either way, it seems like you won't have a problem if you keep doing things the same way.

Steve

Al Basham wrote:

Reply to
Steve Smith

Your electrician may be concerned that he could be criticized for installing more load on the feeder to the inverter than the cable/overcurrent can handle. It's safe enough if you're the only operator and don't ever make any mistakes, to have everthing connected, but he has to be concerned about "the other idiot". You're right up to the limit on that inverter though. Rule of thumb for motor starts is 200% full load current, and the surge may be beating up on the inverter. Be careful not to start that lathe under load.

MadDog

"In the pursuit of Design for Public Safety, the best you can do is to guard against someone doing the stupidest thing you can imagine. Satisfied that you have done this to the best of your ability, you must simply, fearfully, await the inevitable appearence of the fool who does something more stupid than you could have ever imagined."

Reply to
MadDogR75

Hi Al

You have some faulty information. Since the "three HP Leeson

Perhaps the electrician wasnt interested in doing the task you asked him to do. His experiences have possibly made him Very cautious. I'd recommend Bob Swinney's method of building a dedicated 3 phase junction box with breakers for each tool. It is difficult for me to believe you couldnt make all the wiring yourself, without an electrician. I'm sure Bob will give you all the assistance needed to duplicate his shop wiring.

Jerry

Reply to
Jerry Martes

Actually, the Leeson is an inverter, not a rotary converter:

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Steve

Reply to
Steve Smith

I see no reason you can't use the drop method. Just parallel off the Inverter for as many outlets as you like. I assume you merely use the inverter for 60hz 3phase power and don't use the variable speed much. Just remember not to try and plug reverse any machine, it will likely trip the inverter.

Reply to
Marty Escarcega

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