Phase Rotation for Power Inlet

[mkgrady]

I'm looking at putting a Power Inlet Panel (PIP) on a building so it can be powered with a portable generator during an outage. The system is 120/208 and the PIP will be powered by a 60KW portable.

The portable will be delivered and set up by a company that rents, delivers, fuels and sets up the temporary connecting cables between the PIP and the generator.

My question is how do they deal with phase rotation? Other than looking for a three phase motor and bumping it to see if they guess right, is there a better way? Are these guys just used to doing this? When I do a cutover I use my rotation meter and make sure I get it to be the same but with no normal power available that won't work.

 

[jim dungar]

When I do a cutover I use my rotation meter and make sure I get it to be the same but with no normal power available that won't work.

Use your phase rotation meter now. Put a permanent placard on the inlet showing the connections you need to mimic your present rotation.

 

[mkgrady]

Use your phase rotation meter now. Put a permanent placard on the inlet showing the connections you need to mimic your present rotation.

Thanks for that. How do I know the generator crew will connect their meter the same way?

When I check before and after rotation I make sure I put the test leads on the same way before and after the cutover. They will be using a different meter. Are the leads standardized so I could indicate how I connected and they could mimic what I do?

 

[infinity]

Thanks for that. How do I know the generator crew will connect their meter the same way?

If the genny guys are that unsophisticated you will probably have other problems too. :roll:

If you really want to dumb it down you could put a small 3? motor right by the inlet with a clearly indicated direction of rotation. They can try running that motor first without turning on any other loads to see if they got it right.

 

[GoldDigger]

If you label your phase wires A, B, and C and make sure that you label the wires the same way at the PIP, based on the transfer switch connections, you should be OK.


Any (working) phase rotation meter with its A, B and C (or X Y Z) leads attached to the same points will display the same rotation reading.
The standard of the time sequence of the positive sine wave peak is common to all meters.
Remember that ABC, BCA, and CAB are all the same rotation direction and CBA, ACB, and BAC are all the opposite rotation.
The only thing you really need to worry about is that you match the labels on the corresponding inputs to the transfer switch.

Tapatalk!

 

[mkgrady]

If the genny guys are that unsophisticated you will probably have other problems too. :roll:

If you really want to dumb it down you could put a small 3? motor right by the inlet with a clearly indicated direction of rotation. They can try running that motor first without turning on any other loads to see if they got it right.

I actually thought about that and hoped to come up with something better but that sure should work.

 

[GoldDigger]

The nice thing about that method is that the generator crew does not even need to have a meter!
Don't forget protection for the motor wiring though.
For safety you can connect to the PIP side of the transfer switch so that they do not even have to open your other loads before testing.


Tapatalk!

 

[electric_cal]

There are many phase sequence indicators out there. You could mount one on the panel which would verify correct rotation during normal and emergency conditions. This would help prevent a reverse phase situation during emergency power.

 

[mkgrady]

If you label your phase wires A, B, and C and make sure that you label the wires the same way at the PIP, based on the transfer switch connections, you should be OK.


Any (working) phase rotation meter with its A, B and C (or X Y Z) leads attached to the same points will display the same rotation reading.
The standard of the time sequence of the positive sine wave peak is common to all meters.
Remember that ABC, BCA, and CAB are all the same rotation direction and CBA, ACB, and BAC are all the opposite rotation.
The only thing you really need to worry about is that you match the labels on the corresponding inputs to the transfer switch.

Tapatalk!

I get all that but my meter has red white and blue leads. I could give instructions to the genny guys to hook up their meter exactly the same as I have but if their meter doesn't have the same colors or they do but the colors don't correspond to the same reference, I haven't shown them what they need. There is something I am not understanding.

I could just add a meter to the cost of the job and leave it there with instructions on what leads go on what terminals but I doubt it would stay there very long.

 

[mkgrady]

There are many phase sequence indicators out there. You could mount one on the panel which would verify correct rotation during normal and emergency conditions. This would help prevent a reverse phase situation during emergency power.

I'll serif I can find one. Thanks

 

[iceworm]

Slow poster: Adding to electric_cal's response
What are you using for a transfer switch? If it is an automatic transfer switch, maybe a reverse rotation protective relay in the transfer control circuit. They are pretty inexpensive.

http://www.ssac.com/products.php?cat=64


If a manual transfer sw, maybe connect the reverse rotation relay to red/green pilot lights.

ice

 

[iwire]

I get all that but my meter has red white and blue leads.

That is typical but forget the colors, most are labeled L1, L2, L3.

I just use a sharpie and mark the direction on the gear.

 

[kwired]

Slow poster: Adding to electric_cal's response
What are you using for a transfer switch? If it is an automatic transfer switch, maybe a reverse rotation protective relay in the transfer control circuit. They are pretty inexpensive.

http://www.ssac.com/products.php?cat=64


If a manual transfer sw, maybe connect the reverse rotation relay to red/green pilot lights.

ice

Almost got through current posts without someone touching on my idea - any phase monitor could be connected to either simply indicate proper rotation or to lock out transfer if rotation is incorrect.