Zog

I commisioned a 60,000HP motor once, big SOB. Used to suck all the air out of a building they tested jet engines in.

Zog

Suprised it took so long for someone to state the obvious, get a phase rotation meter.

John Valdes

Will not work with a VFD. Also the plant would have to have every panel, disco or lug block phased exactly the same way for the phase meter to be of any help. Personally I have never seen one help anyone. And have never seen a plant that had everything phased exact. Never. Some think they do, but they don't. Rotation on a 3 phase motor is 50/50. No better, no worse.

Set the ramp speed on the VFD to the highest setting possible. Most likely 999 seconds. Determine the correct rotation. Start the compressor. As soon as it starts to move shut it down. Now, you know if the leads must be reversed on the load side of the VFD. Or, you can change rotation in the parameters, provided you can change the interface to match. Meaning if the motor is going in the right direction, the control should not say its going in reverse.

drsparky

If you check rotation before you terminate a motor how do you get a 50/50? more like 100% chance of having it correct.

__________________
"Whatever is felt is within suffering."

Lone Crapshooter

Theway I check 2400 volt is with temporary insulation. I have 2 pieces of 15KV heatshrink that are shrunk on some PVC pipe . I make up 1 lead and eather heatshrink or tape it. Then I slip the temporary insulation over the other 2 leads and use a few quick raps of 88 to hold it on. Now this temporary insulation are about 12" long and our 2400 volt is unshielded.
Also the millwrights leave the coupelings broken when we bump the motors.

John Valdes

You misunderstood my comment. In advance, you must know which way the motor should turn. Some people put an arrow on the machine so they know what direction it should turn. Determining the direction you want it to turn is the first thing you do.

drsparky

A rotation meter will show you the direction the motor will turn. It will also show the phase relationship of the motor leads. 100% chance of making the connections correct the first time.
Without a phase meter, yes it is 50%.

__________________
"Whatever is felt is within suffering."

MDShunk

No, since my name is Marc, my chances increase to about 90% getting it wrong.

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micromind

That's true for guys named Rob too!

Rob

InControl

Yes


Yes



Ahhhh, I see that you haven't met Mr. Murphy! He says otherwise. Mr. Murphy says that there is no such thing as 100%. I tend to agree.

So you're saying that there's a 100% chance that 'YOUR' T1, T2, T3 on the motor will match up with the 'manufacturers' T1, T2, T3 on the VFD.

Good luck with that line of thinking......

drsparky

True, Murphys law can effect anything, a software error or a wiring error in the VFD can make for trouble. The power company can switch phases just before I power up a motor and the magnetic poles on the earth can swap. You can't plan for everything. My point is that with proper use of a rotation meter you can be 99% sure that the rotation is correct. This verses a 50/50 chance without use of a meter. Many terminations are not easy to swap. It can take an hour to change two of the three terminations.

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John Valdes

Dr., Whats a rotation meter? Is it the same as a phase meter? I have never used one if it's different. I can only go by past experience. When starting a 3 phase motor, you have 50/50 chance you will get it right the first time. I have seen people use phase meters with the same success. 50/50. Thats why I have never had any faith in the phase meter. Just never saw one work. I'm old school. If ya can't bump it, uncouple it.

If this is a meter that you are familiar with, I am all ears and would like to know more about it. Maybe point me to one? A link? Thanks John

drsparky

Here is a few links, the first is hardware the second is a “how to” and theory.
http://www.mygreenlee.com/Products/m...c_number=07576
http://ecmweb.com/mag/electric_deter...otor_rotation/

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"Whatever is felt is within suffering."

electricalperson

can you mark the motor leads ABC, trace each wire out and mark the leads feeding the drive ABC?

micromind

As I know them, a rotation meter is a device that is connected to the leads of an unpowered motor, the shaft is turned by hand in the desired direction, and the meter will indicate whether CW (ABC) or CCW (CBA) phase rotation will cause it to turn the same way.

A phase sequence meter is connected to a 3 phase power source, and it reads the phase sequence, or phase rotation. CW (ABC) or CCW (CBA).

Quite a few years ago, I built a rotation meter from a couple of gate chips and some other stuff. It's powered by a 9V battery. It has 3 LEDS, and a pushbutton. One LEDs lights when the button is pushed and the battery is good. When the shaft is turned, one of the other LEDS will light. Either the one for ABC, or the one for CBA, not both.

As far as I know, all phase sequence meters will show the same rotation. If the source is ABC, every meter will show it as ABC.

I've used my rotation meter hundreds of times over the years, it's yet to be wrong.

Here's how it works; first, the rotation of the source is determined. This is best done at the starter. If proper wire colors are maintained throughout the building, then the whole buildings rotation will be the same. Suppose it's ABC.

Next, the rotation meter is connected to the motor leads. This is best done before the wire from the motor to the starter is connected. This meter works at VERY low voltage and current, it doesn't take much to make it not work. Once connected, the shaft is turned by hand. One of the lights will light. Suppose the CBA one does. This means that the source rotation and the desired motor rotation are different. I then know to reverse the rotation at the motor. Suppose the system is 480. I would connect brown to T3, orange to T2, and yellow to T1.

The motor will then turn whatever direction I turned it by hand.

Obviously, there's no point to doing this with a small motor that's turning a fan, and takes 10 seconds to reverse, but a big motor that's a major pain to change.....

Rob

drsparky

Exactly, thank you for your explanation, I was getting tired of beating this dead horse.

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MDShunk

Pretty tricky if you're dealing with primary. Takes a whole other type of phaser.

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InControl

My point is..............ta da.....your ASSUMING that the phase rotation will match that of your VFD. The VFD does not care which way is up, as it does which way is clockwise.....The VFD does as its told, clockwise for one, counterclockwise for the other.

John Valdes

Okay heres what I have learned from this discussion. A rotation meter will enable you to predict with 100% accuracy the direction a motor will turn before you power it up, but only when using across the line starting? If it's going to be connected to a VFD all bets are off? Did I get it or not?

p_logix

With a VFD all bets are off!

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p_logix
"Meggers Don't Lie, Electricians Lie". Go LAKERS!!!!