More three pahse motor questions...!

Status
Not open for further replies.

dodiho

Member
You guys are great-I have less than an hour for lunch...I want him to pay! So: another "dumb" question from a real rookie...#1: how do u reverse the rotation on a 3 phase motor( I' thought you'd just swap two leads!) #2: when checking a 3 phase motor with a meter-what constants-voltage- should be between A to B,B to C,etc.? I think they should all read the same... still working on the 30 degree formula thing-he wasn't clear--but it had to do with bending EMT....dodiho
 

69boss302

Senior Member
Re: More three pahse motor questions...!

For a typical 3 phase induction motor, yes you reverse any two of the Line leads. Be careful this is a general statement. Some three phase motors are a little different and also make sure it's the line leads. Dual voltage motors and such have more than 3 leads coming out of the motor.

Voltage across phases will depend on incoming line voltage and I don't think I have ever seen them exactly the same, but a rule of thumb is they shouldn't deviate by more than 10%. Generally they will range within 5 to 10 Volts of each other.
 

engy

Senior Member
Location
Minnesota
Re: More three pahse motor questions...!

Just a guess...
Bend the conduit so the end of the conduit is bent up off the floor a distance of 1/2 the distance from the end of the conduit to the bender. =30 degrees

[ January 17, 2006, 04:46 PM: Message edited by: engy ]
 

jbwhite

Senior Member
Re: More three pahse motor questions...!

Originally posted by dodiho:
#2: when checking a 3 phase motor with a meter-what constants-voltage- should be between A to B,B to C,etc.? I think they should all read the same.
I have seen them all read different including phase to ground. The question is how much different.
 

jbwhite

Senior Member
Re: More three pahse motor questions...!

Originally posted by 69boss302: For a typical 3 phase induction motor, yes you reverse any two of the Line leads. Be careful this is a general statement. Some three phase motors are a little different and also make sure it's the line leads. Dual voltage motors and such have more than 3 leads coming out of the motor.
For a drive this will not change the direction of the motor, this is most easily done in the software. It can be done on the load side of the drive. For a standared starter, it can be done anywhere in the circuit.
 

jbwhite

Senior Member
Re: More three pahse motor questions...!

Originally posted by engy:
Just a guess...
Bend the conduit so the end of the conduit is bent up off the floor a distance of 1/2 the distance from the end of the conduit to the bender. =30 degrees
If you dont have a protractor handy, for a hand bender use the marks that the mfg put on the side of the bender. For larger conduit, buy a protractor.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Re: More three pahse motor questions...!

Originally posted by jbwhite:
Originally posted by engy:
Just a guess...
Bend the conduit so the end of the conduit is bent up off the floor a distance of 1/2 the distance from the end of the conduit to the bender. =30 degrees
If you dont have a protractor handy, for a hand bender use the marks that the mfg put on the side of the bender. For larger conduit, buy a protractor.
Or buy one of these:

880indx.jpg
 
Status
Not open for further replies.
Top