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Electric motor rotation #170277
10/30/07 08:13 PM
10/30/07 08:13 PM
C
Cinner  Offline OP
Member
Joined: Dec 2004
Posts: 78
Kelowna, B.C., Canada
Is the correct rotation of a motor always marked on the exterior of the motor?

Work Gear for Electricians and the Trades
Re: Electric motor rotation [Re: Cinner] #170279
10/30/07 08:24 PM
10/30/07 08:24 PM
N
NORCAL  Offline
Member
Joined: Sep 2002
Posts: 876
IMO, the rotation should be marked on the equipment powered by the motor.

Re: Electric motor rotation [Re: NORCAL] #170300
10/30/07 10:32 PM
10/30/07 10:32 PM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
In most cases yes.
Provided no-one has modified the connections in the terminal box for you.

Re: Electric motor rotation [Re: NORCAL] #170301
10/30/07 10:35 PM
10/30/07 10:35 PM
L
leland  Offline
Member
Joined: Aug 2007
Posts: 853
Lowell area, Ma. USA
Originally Posted by NORCAL
IMO, the rotation should be marked on the equipment powered by the motor.


Agreed. Motors power equipment.

Re: Electric motor rotation [Re: leland] #170352
11/01/07 12:20 PM
11/01/07 12:20 PM
J
JValdes  Offline
Member
Joined: Jun 2007
Posts: 301
South Carolina
Three phase motors are NEVER marked for rotation. They are designed to go either direction. You choose the direction you need.
Pumps/fans/ect... have an arrow or some marking to allow it to operated properly.

Some applications I have worked on, call for the motor to use both directions on the same piece of equipment.


Re: Electric motor rotation [Re: JValdes] #170472
11/03/07 08:37 PM
11/03/07 08:37 PM
J
jraef  Offline
Member
Joined: Jul 2004
Posts: 101
San francisco, CA, USA
What good would it do to mark the motor? The motor mfgr. has no idea how you are going to hook it up or what the incoming line sequence is at your facility. ABC is relative. For instance, PG&E here in California is A-C-B with relation to other facilities in the US, but that means nothing to everyone local here. It just is what it is.

CBS: Connect it, Bump it, Swap leads if needed


JRaef
Re: Electric motor rotation [Re: jraef] #170482
11/04/07 09:25 AM
11/04/07 09:25 AM
togol  Offline
Member
Joined: Sep 2005
Posts: 421
NW In. USA
yep,

just make sure the load is disconnected before bumping

some things don't like going backwards


Tom
Re: Electric motor rotation [Re: togol] #170483
11/04/07 10:04 AM
11/04/07 10:04 AM
J
JValdes  Offline
Member
Joined: Jun 2007
Posts: 301
South Carolina
jraef,
Correct my friend. When I supervised a motor shop some years ago, some customers would call and ask if we could mark the leads, so the motor would turn in the direction they wanted without "bumping". Of course we could not garranty rotation on three phase.
There are some phase detectors on the market that claim they can do this. But how can you know the complete facility is phased exact at every panel, disco or motor starter. I have even seen some companies try to do this. I have never found any of them to be successful.

Now, DC motors can be wired for a particular direction, but it must be a "shunt wound, compound wound or series wound motor.

Re: Electric motor rotation [Re: Cinner] #170488
11/04/07 10:38 AM
11/04/07 10:38 AM
electure  Offline

Member
Joined: Dec 2000
Posts: 4,264
Fullerton, CA USA
In my experience, 3Ø motors will rotate the way you don't want them to about 95% of the time.

They'll rotate the proper direction the other 5%. laugh

Tom has a good point....some machinery doesn't take well to being rotated backwards.

Re: Electric motor rotation [Re: electure] #170490
11/04/07 11:54 AM
11/04/07 11:54 AM
J
JoeTestingEngr  Offline
Member
Joined: Nov 2005
Posts: 791
Chicago, Il.
On the other hand, some motors work too well backwards. Our bus garages use 5 HP Red Jacket STPs in our underground storage tanks. (USTs) I always tell our electricians to check them both ways after replacement. I ask them to check static pressure and to squeeze off 10 seconds and check the flow rate. More than once, they've told me they didn't bother because it looked fine. I jumped on them about why I would waste my time asking them if I didn't feel it to be important. At least half the times, they've called back telling me that they got higher pressure and flow after switching the leads.
Joe

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