Respectfully RE: 3 phase six lead two speed motor burnning down the house! Problems with the contactors may show up as high and unbalanced currents. High, balanced currents may indicate a mechanical problem. Something dragging, or a lack of lubricant.Ĭheck the currents. I would check the circuit to see if the push button may be bypassing something that is in the circuit when the PLC is controlling. I have found that information such as "It works on the push button" to often be misleading.ĭon't let this information distract you from complete trouble shooting. Any voltage across a closed contactor is a sign of contact failure. As a matter of course, I would check across each pole of the energized contactors with a voltmeter. The next thing is to verify that the PLC outputs are getting to the contactors. The first thing to check is to see if a contact has welded closed in one of the contactors. It was only when they switched the machine into auto did it fry itself.ĭo you see any other ways this motor could self destruct? RE: 3 phase six lead two speed motor burnning down the house! waross (Electrical) 8 Sep 06 22:31 I was told tonight that the motor ran fine on the slow setting using my push button controls. The next idea I have is that mabe the short contactor has a bad contact in it and one of the legs is not getting connected durring the fast run cycle. If the slow contactor sticks or shorts across a contact while the motor is in fast operation it would introduce 480 into the windings that should be shorted. I've set here and looked at the drawing, It appears to me that there are a couple of combinations that could cause the motor to burn up. A lift contactor, a lower contactor, a fast contactor, a short contactor that shorts U1,V1,W1 when the fast contactor is energized, a slow contactor that puts voltage to U1,V1,W1 and finally a brake contactor that releases the brake.Ĭombinations to run the motor are as follows, (Lift, slow, brake lift, fast, short, brake ) exchange lower for lift in the above two for lowering the pallet.
this particular motor utilizes 6 contactors. So old that you cannot go online with it to trouble shoot (It needs a ram chip to replace the eprom to do so) The machine has no home run program and about a year ago I put in a push button station to manually fire the contactors to get parts of the machine back to basic position. This motor moves a pallet lift up and down and utilizes both speeds. It has six post to connect wires to and they are labeled U1, V1, W1, U2, V2, W2. This motor is an SEW gear drive motor, 4.5/5.0 hp. I have a motor that my electricians have managed to burn up three times in the last week. Last year I moved more into a managment role and have started working on my EE. I have worked as an elecrician for the last 17 years, primarily in industrial maintenance.