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Can I use a 3 phase breaker panel instead of a fused disconnect at each machine?

catch22

Aluminum
Joined
Sep 23, 2006
Location
CANADA
I am going to be using a rotary phase converter to power my machines with 230v 3 phase power, can I use a 3 phase breaker panel instead of a fused disconnect at each machine?
So I would be running my 1 phase power to the RPC then running out to the 3 phase panel then from there to each machine.
Not sure if this will work with the phase coverter or not?

Thanks Mike
 
In this case, the three-phase panelboard and breakers would provide feeder protection, not disconnections, unless each load was 2 HP or less and the panel was with 6 feet of every machine.

I still think you have to provided a disconnection means at each machine. Perhaps only a non-fused disconnect switch. A cordset, if 2 HP or less.

Each machine must, of course have its own motor controller means and motor overload protection means.

The code is quite cryptic because it assumes the worst case which is a multi-motor machine which is, in the sum, more than 2 HP, and a feeder which is an indeterminate distance, but presumably begins very long distance from the machine.

Perfectly reasonable for a 1,000,000 square foot factory in a great many spaces, where no one can see the panel and there are hundreds of operators, but perhaps overly complex for a 200 square foot shop in one space, where the panel can be seen from everywhere in the shop and there is only one operator.
 
That is how I did it. Just feed the panel where the main would normaly go. I fed the wild leg to the middle buss. It makes it easy to keep track of it as it matters where it goes on some machines.
 
That is how I did it. Just feed the panel where the main would normaly go. I fed the wild leg to the middle buss. It makes it easy to keep track of it as it matters where it goes on some machines.

Sorry but I am a bit lost, If you dont mind could you explain how you did it in a little more detail?
Just starting out with this stuff.

Thanks Mike
 
The three busses must be A, B and C, left to right or top to bottom.

A and C correspond to L1 and L2, the real phases.

B is always the manufactured phase, and is always the middle bus, no matter what the orientation of the panelboard.
 
I still think you have to provided a disconnection means at each machine. Perhaps only a non-fused disconnect switch. A cordset, if 2 HP or less.

Each machine must, of course have its own motor controller means and motor overload protection means.

Peter, does a start/stop switch qualify as a disconnect? Or does it have to completely disconnect all electricity from the machine?
 
"Peter, does a start/stop switch qualify as a disconnect? Or does it have to completely disconnect all electricity from the machine?"

It can.

The drum switch controller on a small lathe qualifies as a disconnect and as a motor controller as in the OFF position all power to the motor is removed.

However, I usually use a cordset as the disconnect, if 2 HP and under, and I use a safety switch, if over 2 HP.

A problem with a drum switch is it seldom can be locked-/tagged-out. A safety switch can almost always be locked-/tagged-out.
 
The three busses must be A, B and C, left to right or top to bottom.

A and C correspond to L1 and L2, the real phases.

B is always the manufactured phase, and is always the middle bus, no matter what the orientation of the panelboard.

So can I use a 3 phase breaker panel with flip breakers with the RPC and use the proper amp breaker so that the motor will be protected, or is this with a disconnect fuse panel?

Sorry Im really new when it comes to 3 phase.

But thankyou for your help!

Mike
 
A panelboard receives power on a feeder and then it distributes power to other feeders.

Feeders are protected at their source by a breaker equal to the capacity of the feeder.

There are allowances for hard-to-start loads, in which case the breaker may be oversized by one increment (20 amps instead of 15 amps, etcetera).

Nothing prevents one from installing, say, a 15 amp breaker for a 12 AWG feeder which would normally be protected by a 20 amp breaker.

Within reason, small capacity breakers may be used to control loads, particularly if of lower capacity, say, 20 and 15 amps, and particularly if within eyesight and six feet from the load.

Some panelboards and their breakers have lock-out/tag-out adapters available for them, and that could obviate the need for such on a load machine.
 
A panelboard receives power on a feeder and then it distributes power to other feeders.

Feeders are protected at their source by a breaker equal to the capacity of the feeder.

There are allowances for hard-to-start loads, in which case the breaker may be oversized by one increment (20 amps instead of 15 amps, etcetera).

Nothing prevents one from installing, say, a 15 amp breaker for a 12 AWG feeder which would normally be protected by a 20 amp breaker.

Within reason, small capacity breakers may be used to control loads, particularly if of lower capacity, say, 20 and 15 amps, and particularly if within eyesight and six feet from the load.

Some panelboards and their breakers have lock-out/tag-out adapters available for them, and that could obviate the need for such on a load machine.


Ok thanks Peter
I think I will go with the disconnect fuse panel at the machine!

Thanks Mike
 
I think you have made the right decision, but to back it up think of it this way:

If someone is working on a tool and gets their sleeve caught, do you want to have to run to find the breaker panel and figure out which one to flip? Even if you flip them all, Murphy's law says it will be the LAST one. The alternative is that a fused disconnect local to the machine is easily identified and very easy to operate to kill power. You typically have a big red or orange handle that can be operated with a broom handle if necessary. In addition when you are working on that machine, don't you want to be able to glance over and SEE that the power is off and a padlock is in place before you start sticking your hands in it?

That's why they call them "Safety Switches".
 
Mike,

It sounds like you have it figured out, so to speak. My question is, how are you controlling or starting each motor on each machine. You have the circuit protected and the motor, sort of! What device are you using to start the motor across the line, at the machine.

It doesn't sound like you're using a motor stater with overloads so you must be using a switch. Whatever you're using to control the motor must also be horsepower rated to that motor. Don't expect to flip a breaker on and have the machine spring to life, you will need a drum switch or something. Does this make sense.

Maybe I missed this in the thread and it has already been addressed.:)

Stuart
 
"The alternative is that a fused disconnect local to the machine is easily identified and very easy to operate to kill power."

Exactly, precisely! ... to quote Charlie Chan, the mythical Chinese detective.

I typically look for three-phase fusible safety switches at electronics/computers flea markets and then buy them for cheap.

New, well that costs SERIOUS cash.

Used, well that costs perhaps $5 ... $10 at the most. Perhaps three for $10.

I prefer three-phase switches, even for my single-phase machines with VFDs, as I can wire the line side of the VFD to the load side of the safety switch as if it were three-phase, and then wire the line side of the switch as if it were single-phase.

This method allows for almost instant conversion to three-phase line power with almost no changes to the machine.
 
peterh5322,

I must not be clear on your last post. Are you indicating that you switch your lathe or drill press or whatever ON and OFF with a safety switch, a knife switch!

This is the device that turns the machine on, then off when the task is done!:confused:

Stuart
 
Mike,

It sounds like you have it figured out, so to speak. My question is, how are you controlling or starting each motor on each machine. You have the circuit protected and the motor, sort of! What device are you using to start the motor across the line, at the machine.

It doesn't sound like you're using a motor stater with overloads so you must be using a switch. Whatever you're using to control the motor must also be horsepower rated to that motor. Don't expect to flip a breaker on and have the machine spring to life, you will need a drum switch or something. Does this make sense.

Maybe I missed this in the thread and it has already been addressed.:)

Stuart

After I come out of the disconnect I will wire into a switch with forward,reverse and ofcourse off also. Now you are probably right and I will use a drum switch unless there is something else that I could use for this.

Thanks Mike
 
Heres another question for you guys.
Can I use a 3 POLE 100 AMP 240V DISCONNECT SWITCH and just change the fuses to whatever I need,or say it was a 660V disconnect could I still run 220V into it and use 220 fuses or am I way out of line here?

Thanks Mike
 
Mike,

Yes you can do that! If the device is rated for more than your intended use, and you can find appropriate size fuses, you are all set.

Stuart
 
And you can buy adapters that slide onto the ends of smaller fuses so that they will fit the larger clips in the bigger disconnect.
 
A reversing drum switch, or a pushbutton station is not a means of disconnect, a safety switch, or a breaker lockout permanently installed on a circuit breaker is, the breaker lockouts are avail. for most major brands of circuit breakers, search for accessories on the site of what ever manufacturer of breaker one is using.
 
Mike,

Where is all this activity taking place...in your garage or home shop? This NEC stuff can be loosely interpreted if you aren't in a large industrial setting with lots of employees and OSHA people crawling around. You can be electrically safe and sane without getting anal about it.:crazy:


Stuart
 








 
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