Temp power with 3 phase generator

[ultramegabob]

Does anyone have a tip on how to tell if you are connecting a three phase generator in the correct rotation without climbing up on the roof and looking at which way the motors are spinning?

 

[masterinbama]

I use one of these. Of course you have to be able to test utility power before it's shutdown.

http://www.globaltestsupply.com/c/152/AEMC_PR-1_Phase_Rotation_Meter.html

 

[ultramegabob]

I have been calling all the suppliers in my area, and none of them stock phase rotation testers, and I need one before Saturday.... I was hopeing there was another trick to figguring it out. I may have to make some calls and see if I can find someone to borrow one off of....

 

[winnie]

The following are potentially 'jack leg' ideas, as I have no direct experience with what you are doing.

1) Use a small three phase motor temporarily connected as a phase rotation meter.

2) Build a set of 'synchronizing' lights, such as are used to parallel generators with the grid (of course you won't have the big switch to actually parallel the generator with the mains, just the lights). If your phase rotation is correct, then you should be able to get _all_ the lights off at the same time, indicating synchronization. If the phase rotation is correct but the frequencies are slightly off (most likely the case), then the lights will flash, but _all_ will be off at the same time when they flash off. If the phase rotation is not correct, then only one light will be off at a time.

3) A search for 'phase sequence indicator circuit' quickly finds: http://www.edn.com/contents/images/6347253f3.pdf

Seriously, McMaster lists a "phase-sequence meter", item 7264K4, as in stock for $80. If they have it in stock, they can get it to you yesterday I have not used this meter, but have dealt with McMaster when I need items quickly.

-Jon

 

[zbang]

The instructions for a Fluke T+Pro tell how to do phase rotation checks, although I haven't tried them. I'll bet the T+Pro is easily available, and they're a great tool.

 

[ultramegabob]

thanks for the responces, but I got lucky and a buddy of mine has one that he will lend me. I am going to order one so this wont be an issue again

 

[masterinbama]

thanks for the responces, but I got lucky and a buddy of mine has one that he will lend me. I am going to order one so this wont be an issue again

I would get one of these then. At least I think this is the one I have.It will tell you the correct connection of a motor before termination and energizing.

http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=5770117&gclid=CI6rorbpip0CFRtO2godOSXq3g

 

[SPARKS40]

I have been calling all the suppliers in my area, and none of them stock phase rotation testers, and I need one before Saturday.... I was hopeing there was another trick to figguring it out. I may have to make some calls and see if I can find someone to borrow one off of....

The big orange stocks the Ideal #61-31, which will meeasure phase rotation. It retails for around $99

 

[hillbilly1]

Don't use the condensor fans as a guide, they are usually single phase, even the 480 volt ones, the air handler though is usually three phase. If you have a Grainger industrial supply nearby, they are pretty good at having one in stock or can have it next day for no more cost. If the store your working on has a cardboard bailer, it is easy to check rotation there, instead of climbing on the roof. If you have a couple of Fluke 87's laying around, take the positive lead from one to "A" phase on the utility, with the negative lead going to "B" phase on the generator side, with the other meter, go to "B" phase utility with the positive lead, go to "C" phase on the generator side with the negative lead. With the meters on ac, watch the bar graphs on the bottom of the displays, if they scroll the same direction, they have the same rotation, if they scroll opposite directions, rotation is opposite.