Do you or your company have a PdM program, yet blindly accept motors from either the vendor or the rewind shop? How do you know what kind of motor they’re sending you and what kind of shape it’s in? Do you know if the motors you’re receiving are within your facility’s PdM specs? Does your facility have PdM specs?

One of the great advantages of having a PdM program is being able to determine if the equipment and materials coming into your facility are going to work when needed. Most PdM programs are very good at finding problems with running equipment, after it’s been installed. But how many times has a “new” motor given the maintenance department problems?

Motor Circuit Evaluation (MCE) can weed out motors that do not meet basic specifications. Especially if there have been specifications dictated to the vendors and rewind shops. Any functional PdM program that utilizes Electric Motor Testing (EMT) will have minimum and maximum values that a motor cannot exceed or fall below. These values include: resistance to ground, resistance phase to phase, induction inductive imbalance, capacitance to ground, and voltage and current; but we’re talking about receiving acceptance testing and commissioning of new motors, not testing on operational motors.

Receiving acceptance testing is exactly what it says; before you accept a motor, test it to ensure that it meets your requirements. If it doesn’t, refuse delivery and send it back. Stand firm on this! If you send the unacceptable motors back, the vendor may raise a ruckus but you’re saving yourself from paying for equipment that doesn’t meet your requirements. There are a lot of motors out there that will start and run, but they may have been one of those Friday afternoon or Monday morning motors where attention to detail was…. well, lacking. They may meet minimum requirements according to IEEE, but are not the best examples of what we call “top of the line.” Don’t feel bad about sending them back, all the vendor is going to do is put you on a list to get the better motors, because you check the motors before they come off the truck. What happens to the returned motors?

With rewound motors, there is a whole other variety of ways things can go off track. If the motor shop is one of the “good” ones, they will test the motor before they accept it to ensure it doesn’t have more problems than just the ones reported. If they are not one of the “good” ones, they may just conduct a “burn out” and tear it down. After the windings have been removed, they may conduct a core loss test to determine if the core is worth rewinding. Very often burn out and removal of the windings causes damage to the core if not done correctly.

If this happens, the motor shop may not admit that they damaged your motor, they may just tell you that the core was damaged and is not worth rebuilding and then offer to sell you a different motor. They may change the method of how the coils are wound because it is easier for them to not change the setup of the machine or to change the type and size of the wire used. Think about it this way; if the OEM spec calls for a total of 60 turns per coil, with the spec being 6 strands, 10 turns. Is that coil going to behave the same as a coil that is made with 5 strands, 12 turns, or 4 strands, 15 turns? Advise the rewind shop that you will test the motors before you accept them and to what specifications you expect the motor to meet.

All of this can, and should, be negotiated when entering into a contract with a motor shop to repair your motors. You may also want to audit the motor repair facility as well as create a mutually agreed upon repair specifications. This can also be used with vendors of new motors as well (very often it is the same location or shop). The Snell Group has helped other customers do these things in the past, so if you need any help, please don’t hesitate to contact us.

Bottom Line: If you are not testing your incoming motors, how do you know what you’re getting?