phase rotation testers

[shanky887614]

anybody use them.

my jtl training advisor wants me to check phase rotation of motors for portfolio.

i don't see the point. the only motors we use are for fans and vsd driven so you can see what way they spin.

i thought fair enough if there not expensive ill have a look but at £100 ill pass

 

[shanky887614]

So once you’ve checked rotation how are you going connect the motor?

40 years of dealing with motors and I’ve never used a rotation indicator.

so it spins in the right direction

ill be honest with you guys, i need one more for completing nvq list becauae the idiots give a long list off loads of things you need to do.


usually i connect cross fingers that o dont have to swap a phase over in isolator

 

[Marvo]

You connect the rotation tester to the motor and turn the motor by hand in the desired direction. The analogue needle settles in either the positive or the negative side of the scale. You then rotation test your supply with the other 3 leads and it will also indicate positive or negative. You make sure your supply rotation corresponds with your desired motor direction.

My tester can be a bit vague on very small motors <2HP. Above that size it's always worked well. We use it mostly on large screw compressors where reverse rotation destroys them.

I see the Fluke one I linked above detects the magnetic fields by proximity rather than being connected directly to the windings so they obviously improved them over the years. They're also about a tenth of the price I paid 2 decades ago so having seen this I'm tempted to get one.


**Edit** I'm almost in tearsat how cheap the Amprobe version is It's obviously using the older technology because you connect to the motor with leads and not just magnetic proximity like the Fluke. At the price though it's rude not to buy two of them if you ask me. http://za.rs-online.com/web/p/phase-rotation-testers/6655909/

 

[Knobhead]

Shanky, see PM.

 

[shanky887614]

Shanky, see PM.

yeah ive checked pm. we usually connect
l1 to u
l2 to v
l3 to w

but because we dont usually run a supply to our panels we don't know if the rotation will be correct

the direction it spins depends on the phase rotation if i remember what my tutor was telling me, (poles usually 120o apart if 3 poles)

:edit

phase rotation not angle as i was quite rightly picked up on.

getting my terminology mixed up lol

 

[Marvo]

If you're machine isn't rotation critical then you can just test run to visually check direction. If it's a fan and it's difficult to physically see it then obviously with an axial you can check if it's sucking or blowing. If it's a centrif or mixed flow it could move air in the same direction regardless of rotation depending on the blade-set but 98 times out of 100 it will have a lower running current in the correct direction plus it will be quieter in the correct direction.

 

[Silly Sausage]

yeah ive checked pm. we usually connect
l1 to u
l2 to v
l3 to w

but because we dont usually run a supply to our panels we don't know if the rotation will be correct

the direction it spins depends on the phase angle if i remember what my tutor was telling me, (poles usually 120o apart if 3 poles)

Eh?

What happens if you swap L2 & L3 say?

 

[shanky887614]

Eh?

What happens if you swap L2 & L3 say?

if reverses direction

it gets pushed/pulled by the poles.

if you swaped them then it would be affected by l3 before l2 so spin in the opersit direction.

 

[davesparks]

There you go then, direction of the motor depends on the phase rotation, not the phase angle

 

[ipf]

yeah ive checked pm. we usually connect
l1 to u
l2 to v
l3 to w

but because we dont usually run a supply to our panels we don't know if the rotation will be correct

the direction it spins depends on the phase rotation if i remember what my tutor was telling me, (poles usually 120o apart if 3 poles)

:edit

phase rotation not angle as i was quite rightly picked up on.

getting my terminology mixed up lol

What if it's 4 pole ?:laugh3:

 

[ipf]

So once you’ve checked rotation how are you going connect the motor?

40 years of dealing with motors and I’ve never used a rotation indicator.

Same here....more money making unnecessaries, IMO.

 

[shanky887614]

What if it's 4 pole ?:laugh3:

wouldnt come across one here mate, 3phase off vsd or built in vsd

 

[davesparks]

I thought poles always came in pairs in motors?

 

[shanky887614]

I thought poles always came in pairs in motors?

nah we have 6 pole motors

 

[davesparks]

Maths not your strong point then shanky?

6 poles is 3 pairs of poles!

 

[Knobhead]

The sensible method is spin the motor before the coupling is fitted.

Get the rotation wrong on some pumps and compressors your going to be changing the unit.