480v motor

[puckman31]

I left some stuff out of my last post I ment to ask about.
In some pm's they ask about voltage on lines 1, line, 2 line 3, does anyone think that is the best way or would l-1 to l-2 than l-1 to l-3 and l-2 to l-3? IS there a size of motor in hp where you would start with pm's?

 

[rhatcher]

puckman31, I would not advise for you to check motor terminal voltages or any other voltages without proper training. To answer your question, the pm's are probably referring to the line-line voltage since this is what matters for a motor. Like you said, this would be measured L1-L2, L1-L3, L2-L3.

 

[puckman31]

I want to thank the person for his reply to my post, but I think he was assumming a little to much. I ask an opinion on a subject that I don't that much about [ pm on motors ]. Please be assured that i am an electrician. Thanks for your reply

 

[cjhut]

puckman, I am also an electrician. I work in a steel foundry with just about every type of motor you could encounter. I didn't see your last page, but to answer your question about a certain size hp you would start with PM's. For the most part, we don't do alot with small 3 phase squirrel cage motore under 3 hp. A typical off the shelf price could be 150-200 dollars. However, I guess it could depend on the type of motor, and the importance of it to the machinery or downtime problems. No matter how small, a motor with brushes should get checked periodically for obvious reasons. Greasing of the bearings is also something you could do. How often depends on the type of bearings in the motor. Some say to never grease because it is a sealed bearing, but rather to change the bearing every 20,000 hrs.It depends on the manufactuter. How about using a megger? This is a good measure of showing that the insulation is breaking down on the windings. We only megger 100 HP motors and up typically. Although we should do smaller ones. Motor's with brakes, need PM'd, no matter the size. That brake is ther for a reason.

 

[puckman31]

Cjhut, sounds like good advice and infomation . Thanks