Quick 3 phase Wiring Question

[Bib Overalls]

I just acquired a 3 phase grinder with a 3 horse power motor. The motor is dual voltage 220/440. The tag says 3.8 amperes at 440 but it does not list an amperage for 220. I will be running it off of a 220 volt 3 phase rotary converter.

I'm thinking the amperage at 220 would be 7.6. Is this correct?

The run from my rotary converter is about 30 feet. What gauge wire should I use? #16?

 

[930dreamer]

Yes, double the 440 amperage.

 

[wyliesdiesels]

I just acquired a 3 phase grinder with a 3 horse power motor. The motor is dual voltage 220/440. The tag says 3.8 amperes at 440 but it does not list an amperage for 220. I will be running it off of a 220 volt 3 phase rotary converter.

I'm thinking the amperage at 220 would be 7.6. Is this correct?

The run from my rotary converter is about 30 feet. What gauge wire should I use? #16?

Yes, current doubles when voltage is halved.

#16? #16 is WAY too small and isnt even available as a building wire. How do u plan on wiring this? Via conduit or NM-B(aka Romex)?

#14 NM-B would work since its rated for 15a. You would need 14/3 NM-B since its 3 phase!

 

[Bib Overalls]

Yes, current doubles when voltage is halved.

#16? #16 is WAY too small and isnt even available as a building wire. How do u plan on wiring this? Via conduit or NM-B(aka Romex)?

#14 NM-B would work since its rated for 15a. You would need 14/3 NM-B since its 3 phase!

Thanks,

The circuit will start in a short length of conduit (2') then transition to NM cable for the majority of the run and end with conduit (4') to the outlet box.

I have a roll of #16/3 W/Ground oil resistant (black rubber casing) cable and I was hoping to save a few bucks by using it.

 

[Norcal]

Thanks,

The circuit will start in a short length of conduit (2') then transition to NM cable for the majority of the run and end with conduit (4') to the outlet box.

I have a roll of #16/3 W/Ground oil resistant (black rubber casing) cable and I was hoping to save a few bucks by using it.

Flexible cord cannot be used in place of permanent wiring.

Flexible cord is listed by the # of conductors, so 16/3 means there are 3 conductors, no "with ground like NM cables.

 

[Bib Overalls]

After posting my 1st reply I did a bit of searching and found this useful calculator.

http://www.jandlelectric.net/motorcalc.html

It gives me #14, which confirms wwyliesdiesels recommendation.

You guys are great! Thank you for the help.

 

[wyliesdiesels]

One more thing: The motor probably isnt 3hp because a 3hp 3phase motor at 460v will draw 4.8a! But the required wire gauge should be the same.