Wiring up a 30HP rotary phase converter

[Oscar]

Decided to use metallic flex conduit to encase the wiring. Got a good deal (naturally, lol) on 1.5" and 1". Not here yet, it's on it's way. You can see the wire bundle on the left consisting of two 2/0 hots, one 4awg ground, and one 8 gauge neutral.

The set-up (for now), which is obviously not physically set-up. Not all breaker's are in place though. Just saying this is what I will be integrating into the cart for the RPC.

The top-right is the 240V 1-Φ disconnect box for everything, with an Eaton BR2125 (on it's way)
Bottom-right is a 240V 1-Φ subpanel that will power the RPC panel (BR2100), and provide power for my other machines via another BR2100 (it will feed my Texas Power Strip)
Bottom left are the RPC panel obviously (which can only accept 4awg at it's input terminals unfortunately), and the 3-pole breaker for the welder.





but the most important thing in all of this are these parts which none of it will work without:














































Now I just have to make the cart for it all. Back to work!

[danielplace]

You can or should probably use EMT and connectors or I guess even PVC on short nipple type connections that do not need to be run in flex. I do not care for flexing between equipment that is mounted on the walls. Guessing some of the runs will be like that on your installation. Even the ones needing flex you can run EMT or I guess PVC(don't love it) and change over to the flex with changeovers if using EMT or female adapter if using PVC. EMT in that size you sometimes use EMT connector then a threaded coupling then you flex connector if you can't source changeovers easily.

[Oscar]

You can or should probably use EMT and connectors or I guess even PVC on short nipple type connections that do not need to be run in flex. I do not care for flexing between equipment that is mounted on the walls. Guessing some of the runs will be like that on your installation. Even the ones needing flex you can run EMT or I guess PVC(don't love it) and change over to the flex with changeovers if using EMT or female adapter if using PVC. EMT in that size you sometimes use EMT connector then a threaded coupling then you flex connector if you can't source changeovers easily.

Makes sense, but like the 2/0 wire that I "stole", I got the aluminum flex conduit ridiculously cheap. So cheap, it wouldn't make sense not to use it, lol.

[danielplace]

Makes sense, but like the 2/0 wire that I "stole", I got the aluminum flex conduit ridiculously cheap. So cheap, it wouldn't make sense not to use it, lol.

By the time you buy the good flex straights and 90°'s there won't be as much savings. It just looks horrible when stationary items are wired with the stuff. I can't do it. Looks like do do and just screams amateur.

[Oscar]

Good, because that works for me! I ain't buying no flex straights nor 90°'s nor nothin. Just the minimum to get by to conceal/protect the wires.

[danielplace]

Good, because that works for me! I ain't buying no flex straights nor 90°'s nor nothin. Just the minimum to get by to conceal/protect the wires.

Huh. Oh sure flex and no connectors. Seriously. I hope you are kidding. Aluminum flex is crap protection but without connectors is just insanity.

Your going to put the wire in flex but no terminations on the flex. What the heck is going to protect the conductors going into the cabinets ? What's going to keep the sharp end of flex from cutting conductors. Duct tape !!! LMAO !!!

Step away from the project and rethink your idea on that one. Lol.

[Oscar]

Huh. Oh sure flex and no connectors. Seriously. I hope you are kidding. Aluminum flex is crap protection but without connectors is just insanity.

Your going to put the wire in flex but no terminations on the flex. What the heck is going to protect the conductors going into the cabinets ? What's going to keep the sharp end of flex from cutting conductors. Duct tape !!! LMAO !!!

Step away from the project and rethink your idea on that one. Lol.

Yes I'm kidding. Remember, this isn't a production shop. It will be just fine for me. I appreciate the concern.

I'll find some fittings at Home Depot/Lowes to obviously route the conductors into the boxes.

[danielplace]

Yes I'm kidding. Remember, this isn't a production shop. It will be just fine for me. I appreciate the concern.

I'll find some fittings at Home Depot/Lowes to obviously route the conductors into the boxes.

Oh thank God. That was a frightening visual.

Aluminum flex I could live with. No connectors or all run in flex are about tie for a epic fail.

[danielplace]

Oscar,
Check out the offset nipples. If some of your panel are going right up close to each other surface mounted they work good as the different cans will always have a little different distance from the wall to center of the knockouts. Where rigid, PVC or EMT straight nipples may not look so hot because of that depth difference.

[Oscar]

Oscar,
Check out the offset nipples. If some of your panel are going right up close to each other surface mounted they work good as the different cans will always have a little different distance from the wall to center of the knockouts. Where rigid, PVC or EMT straight nipples may not look so hot because of that depth difference.

I did, but I didn't like them.

[danielplace]

Yea I don't love them either but when using factory concentric they may help align things. Especially if you may don't have a knockout set to get straight shots where you want them. Sometimes you get lucky and find appropriate factory ones but they are often a compromise from how you would like to set the cans.
A knockout set can often make the job a lot simpler when you need matching larger sized holes where there aren't the proper factory concentrics. You don't have that much going on so may be fine getting them tied together nicely.

[Oscar]

Finally got time to revisit this. Built up the cage.



Using 1/8" sheet for the caster mount plates.

[Oscar]

added casters, then had to flip it over. I need to work out some more, it was a chore to flip over this 400lb behemoth. :lol:

[metalman21]

Please excuse me if it was mentioned previously but what amps at 240 volts (three phase) are required for the Invertig 400?
If I read the specs right the 400 unit outputs 350 amps on single phase 50 amp input which is quite good so should be very efficient on three phase.

[Oscar]

Please excuse me if it was mentioned previously but what amps at 240 volts (three phase) are required for the Invertig 400?
If I read the specs right the 400 unit outputs 350 amps on single phase 50 amp input which is quite good so should be very efficient on three phase.

36A on 230V 3-Φ input power. So at 240V 3-Φ input power should be just tiny smidge less, perhaps 34-35A, for the full 400A welding amperage output.

[scsmith42]

That cage looks pretty stout!

I went the cheap route and just installed the casters directly to the converter frame. In my instance, it's installed in my generator room so there is not much traffic near it.

[Oscar]

Finally getting some more time to finish this darn thing. I know I keep saying that

By the way, does anyone know what purpose this timer serves? I believe it is for the capacitors. I haven't messed with it, but just curious since I did get this thing 2nd hand, so I don't know where it is supposed to be at. Vendor has not returned my emails.

[William McCormick]

Oscar,

Do you have any idea the size and number of houses on the transformer you are getting power from? A number of power companies have a stipulation in residential service about starting any motor over 10HP without calling them.

It is 5hp near me.


Sincerely,


William McCormick

[William McCormick]

Oscar,

Do you have any idea the size and number of houses on the transformer you are getting power from? A number of power companies have a stipulation in residential service about starting any motor over 10HP without calling them.

Is Oscar going to use a smaller 120-volt motor to bring the larger 3 phase motor up to speed? That is what we used to do to avoid the inrush current. God help you if you forgot to get it up to speed.

Sincerely,

William McCormick

[Oscar]

Is Oscar going to use a smaller 120-volt motor to bring the larger 3 phase motor up to speed? That is what we used to do to avoid the inrush current. God help you if you forgot to get it up to speed.

Sincerely,

William McCormick

Isn't that what the starting caps help accomplish, in a way? Besides, there is no visible/protruding shaft on this motor. There is only a cover plate where the shaft would be visible, so there is nothing to "grab onto".

[Willie B]

Isn't that what the starting caps help accomplish, in a way? Besides, there is no visible/protruding shaft on this motor. There is only a cover plate where the shaft would be visible, so there is nothing to "grab onto".

Industry would use a soft start, or a Variable Frequency Drive to ramp up frequency & voltage to start more gently.

[Oscar]

Industry would use a soft start, or a Variable Frequency Drive to ramp up frequency & voltage to start more gently.

Thanks, but no industry here in the garage though.

[scsmith42]

Oscar, a lot of my 3 phase equipment has timers on the start circuits. They are designed to trip if it takes the motor too long to spin up to operating speed. This can occur during a low voltage situation - such as when you're first starting the RPC. That may be what the timer you have is for.

I don't have a pony motor on my 30hp Phase-a-matic RPC, but quite frankly it wouldn't be a bad idea. Current inrush when starting is around 150A.

What William and Willy are referring to is the fact that on industrial power services the utility company bills you for a demand charge. Basically they charge you for 15 minutes worth of the maximum current that you pull. If I had that type of service, every time I started my RPC I would have to pay the equivalent of 150A (current inrush) x 15 min of consumption (even though I only consumed 150A for 5 seconds or so). A soft start, VFD or pony motor drastically reduces the current inrush and thus your power bill.

[Oscar]

So that is on industrial power services, but this is residential, but yes I do see your point. I do remember at one point the vendor said that "soft start" is not needed until one gets to a 60HP RPC size, but I don't know where that info is rooted.

I definitely can't use a pony motor on my RPC. No where to attach to.




What would be the simplest way to get a slow-start on this?

[Oscar]

So I just spoke to the tech at North American Electric, the manufacturer of this motor, and he stated that the LRA (locked rotor amps) is what the max in-rush would be. This motor is rated at 217 LRA, but that is on 460V input. Then technically does this mean that this motor would draw an in-rush of 400A+ on 240V 1-Φ input ? Seems excessive!