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-   -   Power to the wall question about Huangyang RFD (http://www.mechmate.com/forums/showthread.php?t=5675)

Diplocaulus Thu 01 November 2018 08:51

Power to the wall question about Huangyang RFD
 
Hello, basic question but just trying to be sure I'm barking up the right tree. We are installing a 2.2kw spindle with the Huangyang VFD, and I am almost there on parts but want to make sure I am running the power to the VFD correctly. We have a 220 amp breaker with a 3 prong 50A dryer outlet in the wall. Most of the videos I'm seeing show people connecting their VFD to 10 wire gauge from their 220 outlets, explaining that the VFD doesn't actually draw as much power as the 220 outlet will provide. Can I make a plug with the arrangement to the 50A draw pattern (where it looks like a giant version of a 120A plug), and attach 10-3 SO cable to it to make a pigtail from the wall without frying the VFD? I kind of see how this doesn't cause any problems because the VFD will only draw what it wants, but also don't want to overload it. The install guy is coming Tuesday and I have to be ready by then, let me know if pictures will help. Thanks again for the help.

Richards Sat 03 November 2018 22:06

I would suggest that you hire an electrician to wire things up properly. As far as I know, a disconnect box is required for 240VAC circuits. Fuses or circuit breakers in the disconnect box are sized to keep the current low enough to keep the wires from overheating. Then, assuming that the wires are routed through your control box, you would normally separate the incoming power from the outgoing power by using a contactor. To protect the wires gong to the contactor, I always recommend using the proper circuit breaker in the circuit. Here in the United States, that means using a double-pole breaker so that both 120 legs of a 240V circuit are opened by the breaker if either leg has a surge.

An licensed electrician knows the applicable laws. Trust him and do exactly what he tells you.

bradm Wed 07 November 2018 20:03

No, you cannot reasonably use 10-3 SO with a 50A breaker.

Asking to do that does raise some alarm bells, although perhaps not out to electrician level.

The rule of thumb here is essentially to imagine a short circuit. Will a 50A breaker see that as a short, or as a 10 gauge heating element to keep supplying power to?

There are lots of wire gauge references online that will let you know the safe wire sizes from various purposes, and you should also be able to find the National Electric Code referenced in your area.

If you aren't comfortable with those resources, then yes, get someone comfortable like an electrician to look at it.

I note that while you gave the max amperage of the dryer outlet, you did not actually give the amperage of the breakers feeding it, or the gauge of the wire. That is also a hint of that there's more investigation to be done here.

Diplocaulus Wed 26 December 2018 13:09

Alrighty, I was reading diy threads and specs and getting confused about exactly which way to approach this. I'm replying now just in case someone searches this thread later. I was handed the spindle, a "phase converter" that turned out to just be a giant capacitor in a box, and the vfd and started from there. I didn't have specs for amperage on the vfd but eventually found some clues and installed a double pole 20amp breaker with a 10/3 rat tail to the vfd and skipped the phase converter entirely. I didn't wire it into the vfd but there are plenty of manuals out there by people who did.

bradm Wed 26 December 2018 19:29

( 20 amps into 10/3 is just fine! Under some circumstances, 30a would be okay; and 20a into 12/3 would be okay. Well done.)


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