Phase Rotation

Join Date
Sep 2008
Location
Alberta
Posts
40
WARNING šŸ¤· ELECTRICAL NOT PLC

I finally got myself a phase rotation meter cause its so hard to tell a well guarded motor's rotation. I also got tired of sticking tyraps in as well when one got grabbed out of my hand.

But at the first place I used it which is where I am quite a bit and use it the most it was always giving me the wring rotation.

Finally dawned on me to check the mains in the building and the whole place is reverse rotation. šŸ™ƒ

Anyone else ever have an experience with a plant with phases reverse rotated? Far as I can tell no harm done but sure explains why the local electricians are always changing rotation on everything that shows up in the place!
 
In the place I usually attend, although I have a Fluke phase rotation meter, I find the tie wrap method better. Half the motors are rewound or messed about with, cables spliced with wrong colours, extension leads with every permutation of connection. Unless I know it's a machine, where damage can occur, I use the tie wrap method.
Haven't seen the mains supply with wrong rotation, in fact that's about the only place I use the meter, is when connecting supplies.
 
I have seen so many mains reversed I began to doubt there was a standard.

The one standard I have seen followed by most shops is buss bars start at the top.
 
WARNING šŸ¤· ELECTRICAL NOT PLC

I finally got myself a phase rotation meter cause its so hard to tell a well guarded motor's rotation. I also got tired of sticking tyraps in as well when one got grabbed out of my hand.

But at the first place I used it which is where I am quite a bit and use it the most it was always giving me the wring rotation.

Finally dawned on me to check the mains in the building and the whole place is reverse rotation. šŸ™ƒ.........

Iā€™m not sure I understand what you mean by the ā€œwhole place is reverse rotation.ā€ In my experience the rotation is what it is. A motor either turns one direction or another. The utility provides the plant with either CW or CCW.
Please help me understand.
 
It will depend on what way you want the motor to go, I was commissioning a rook of conveyors and 22 of the 31 ran the wrong way, they were all wired exactly the same but due to the difference in the construction of the conveyors those 22 did run the wrong way. I could have either changed the rotation on the inverters or the wiring in the panel, however, to make sure there were no oddities I changed the connections on the motors.
 
Iā€™m not sure I understand what you mean by the ā€œwhole place is reverse rotation.ā€ In my experience the rotation is what it is. A motor either turns one direction or another. The utility provides the plant with either CW or CCW.
Please help me understand.
He's saying the leads were swapped at the main incoming to the plant, so there is ACB rotation instead of ABC rotation. Any leads swapped anywhere in distribution will make everything downstream reversed.
 
He's saying the leads were swapped at the main incoming to the plant, so there is ACB rotation instead of ABC rotation. Any leads swapped anywhere in distribution will make everything downstream reversed.

Exactly. ABC clockwise not CBA or ACB counterclockwise (anticlockwise for you other guys (y) ).

Motor manufacturers and rewinders know the difference and wind for clockwise phasing. If you seem to be reversing your phases all the time in incoming equipment, check for the rotation on the mains. You'll need a meter for that but it will clear up a lot of confusion. Most everything else won't care like VFDs, DC power supplies, etc.
 
I have had a Phase rotation meter for many years. I like the AEMC over the Fluke but itā€™s just a personal choice.
The newer meters work better than the older ones.
I donā€™t use it much anymore I let the install electricians take care of wiring the motors I donā€™t normally get involved unless I see something that need my attention.
As for incoming phase of the service I have never heard of any hard and fast rules for that, it is what it is work with it.
I have seen local code mandate the location of the high leg if there is one also the high is to be tagged with red tape or red wire.
I think your confusion is in how to use the meter. Read the instructions
On a disconnected motor connect A B C to T1 T2 T3 and rotate the motor shaft in the direction you want the motor to run . the meter will display rotation ABC or CBA . then connect the meter to motor 3 phase supply interchange the test leads until you rotation is the same as you want , connect the motor.
I always like to think you have a 50-50 chance of getting the correct rotation the first time I was told it is 2 out of 3 times but it never seems that way.
 
Changing incoming phases is a problem as any motor that is directly driven will run the wrong way, those on inverters will not (this is assuming an existing installation).
The one thing is no matter if all motors are built to rotate clockwise or what ever, many conveyor systems will use different methods of drive or mounting of drive for example a motor mounted on the right hand side will run the opposite of one mounted on the left. this was the case on one system I commissioned.
The reason for the different mountings was space. I do remember one guy said lets reverse the incomer then we have less to change. We all fell about laughing, he did not realise that all the drives were driven by inverters changing the incoming will not reverse the drives.
 
Another thing about conveyor motor direction, when a large or long conveyor is driven by 2 motors, is a carry over from railroads I have seen. This system had 2 25HP motors (one at each end) controlled by synch'd servo controllers and the builder purposely put one motor on the other side to run reverse.



When 2 diesel locomotives are coupled together you will see that they are back-to-back and one is always going in reverse. This is done by design as 2 locomotives pointed the same direction give less power to the wheels than when one is reversed, not so if they want to go the other way they move to the other cab.
 
I one did a plant near San Francisco. When I got on site the contractor complained that nothing would run because none of his fourteen solid-state starters worked! I read the error code on the starters. (Him- "Is that what those blinking lights are?"). You guessed it - phase rotation. I had to swap connections on one blower to prove it to him. Swapped the main transformer and all was good.

o_O Then I had to convince him he had to swap back my test motor. Sigh.
 
He's saying the leads were swapped at the main incoming to the plant, so there is ACB rotation instead of ABC rotation. Any leads swapped anywhere in distribution will make everything downstream reversed.

I have had a Phase rotation meter for many years. I like the AEMC over the Fluke but itā€™s just a personal choice.
The newer meters work better than the older ones.
I donā€™t use it much anymore I let the install electricians take care of wiring the motors I donā€™t normally get involved unless I see something that need my attention.
As for incoming phase of the service I have never heard of any hard and fast rules for that, it is what it is work with it.
I have seen local code mandate the location of the high leg if there is one also the high is to be tagged with red tape or red wire.
I think your confusion is in how to use the meter. Read the instructions
On a disconnected motor connect A B C to T1 T2 T3 and rotate the motor shaft in the direction you want the motor to run . the meter will display rotation ABC or CBA . then connect the meter to motor 3 phase supply interchange the test leads until you rotation is the same as you want , connect the motor.
I always like to think you have a 50-50 chance of getting the correct rotation the first time I was told it is 2 out of 3 times but it never seems that way.


No confusion here whatsoever in how to use my Amprobe. I have also as you outlined used it to phase disconnected motors too. 100% success there. Never got one wrong yet. I like the Amprobe because it even works on thick finned motors inductively.

It is also universal (many different specs) that manufacturers deliver motors that run Clockwise when viewed from the drive/shaft end hooked up to an ABC phasing source. So when you connect the motor to the correct colour phasing for your country, it should go CW on DE, CCW on ODE. Makes life simple when everyone know and follows the rules.

In the original case I stated, the contractor who phased the building should get a crack on the noggin for not phasing it correctly or for even thinking that it didn't matter. It does. That's engineering and the lack of it.
 
My uncle gave me this a long time ago. Someday I'll see if it works.


phaseindicator.jpg
 
In the original case I stated, the contractor who phased the building should get a crack on the noggin for not phasing it correctly or for even thinking that it didn't matter. It does. That's engineering and the lack of it.


I have watched electricians installing service for large machines, a 300HP air compressor and production lines pull 3 unmarked black wires from the switchgear (with a green one so that's not the point) that were not marked and whichever one ended up on which terminal at either end didn't matter to them. They figured the phase rotation needed checked when the power arrived in the control panel when it was connected and everything before that was irrelevant, and not their concern.



OT: On the side I worked at a stamping plant where a foreman for the electrical company we used used UniStrut to hold the 250MCM and larger wires back in junction boxes where everyone else in the world uses wood, and was surprised when the UniStrut cut through and made contact with the 480V copper conductors. The owner of his company asked him why he used UniStrut on this job and he replied "I always uses UniStrut" and was fired as soon as he provided a list of all jobs he has worked on.
 
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ā€œIn the original case I stated, the contractor who phased the building should get a crack on the noggin for not phasing it correctly or for even thinking that it didn't matter. It does. That's engineering and the lack of it.ā€
I can see that you have never worked on a new install or you wouldnā€™t say that.
Will I have when it first started out before the PLCā€™s came out. One of my jobs at the time was to layout and install building services and I can tell you that the contractor / installer never makes the final connection. The way it works is that after the installer sets the service panel and metering equipment it has to be inspected before any power can be applied no power company will allow a connection that doesnā€™t have a certificate. At least in the US. At that point the power company will make the final connection. If itā€™s an underground service then they even pull the wire to the metering equipment. The installer has no control over the phase connection. The only exception to that is if the plant is buying the electric at the primary rate. They have their own service transformers in my area the primary would be 13,000, 66,000 or 120,000 the most common for industrial use is the 66,000

As the unistrut holding the wire I donā€™t know where you are but here no electrician would use wood anymore it hasnā€™t been code for many years. Back in the 20-30ā€™s wood handles on disconnects was common. But itā€™s a fire and shock hazard and is now banned in all new equipment. Even using wood supports is frond on. Over time they can break down and collapse. Although I donā€™ know why it would be used it keep the conductors in the disconnect the cover should be able to do that. But Unstrut is the most common materials used to make racks to hold large conductors or to mount electrical panels. I like to use it to hang wall mounted panels it provides air circulation around the panel and on block walls it helps keep the panel from rusting.
 

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