3 Phase Breaker Tripping

Status
Not open for further replies.
I

INphil

Member
Location
Indianapolis, IN
I recently installed a new 400A service in order to power some new woodworking machinery. 3 Phase service isn't available in this location, so I've installed a phase converter to generate my 3rd leg of power. I have installed the new service, wiring, and machinery but now I'm having an issue when starting one machine.

All voltages are testing as expected (2 legs are reading 120V and the 3rd leg from the phase converter is reading high when it's not under a load - about 270V).

The machine I'm having problems with is a 7.5HP industrial dust collector. The nameplate states the max current draw as 21 amps so I used a 30A breaker with #10 wire. When starting the dust collector, the motor will start and run for about 15 seconds but then the breaker trips. It doesn't ever seem to reach full RPM. I tried another 30A breaker but I'm getting the same results. Does anyone have any recommendations? I'm a total rookie when it comes to 3 phase power...
 
Is the phase converter wired correctly? Also I would probably change the breaker to a 40 amp as long as the motor has overload protection.
 
converter wiring

converter wiring

Yes, I believe the phase converter is correctly wired. I have another 3 phase machine that runs perfectly from it. The motor does have overload protection so I suppose I can try a 40A breaker. I doubt I'll be able to get a 3 pole breaker over the weekend though... I don't think any of the home centers stock them...
 
Amp Draw

Amp Draw

I have not measured the amp draw. Where would I measure this? I assume between the 3 phase panel and the motor? Or would I test between the motor and the thermal overload protector?
 
INphil said:
I have not measured the amp draw. Where would I measure this? I assume between the 3 phase panel and the motor? Or would I test between the motor and the thermal overload protector?
Click to expand...


Test it either at the breaker on each phase or at the motor. What voltage do you get between phases?
 
Testing

Testing

Ok - I'll test the amperage at the breaker. I need to borrow an amp meter because mine is only a 10A multimeter...
On the voltage testing, I'm getting 120.5V between L1 and Ground, and L2 and Ground. Between L1 and L2, I'm getting 241V. L3, from the phase converter is reading high (about 270V) which I'm told is normal when there is no load applied.

I suppose I could turn on the my other 3 phase machine so that there's a load on L3? I'm not sure what that would accomplish though. I assume the high leg should read about 208V?
 
Testing Amp Draw

Testing Amp Draw

When I test the Amp Draw, you said to test each phase. I assume you're saying to test each phase individually? Should I also test them combined?
 
Sorry I see now that you are not an electrician

I am closing this thread, in accordance with the Forum rules. This Forum is intended to assist professional electricians, inspectors, engineers, and other members of the electrical industry in the performance of their job-related tasks. However, if you are not an electrician or an electrical contractor, then we are not permitted to help you perform your own electrical installation work.


If I have misjudged the situation, if for example this project is related to your work, then send me a Private Message. If you can show me that I am wrong, and that you are a licensed electrician (or at least a licensed apprentice), then I will reopen your post, and offer an apology for the delay and inconvenience.

A reminder to all members, if you see a questionable post, feel free to report it by clicking the
report-40b.png
button at the bottom left corner of the post.
 
Status
Not open for further replies.
Top