Frequently Asked Questions
1. What is the difference between a NEMA and Above NEMA motor?
A: NEMA motor have standardized dimensions for the critical mounting measures across all the manufacturers. NEMA frame motors are mostly commonly found in motors below 600V. Above NEMA motors have unique dimensions from manufacturer to manufacturer and are normally used in motors with voltages above 600V.
2. We have variable pitch fans and have wondered about fixed blade units with VFD's. How can we determine which will work best for us?
A: Variable pitch fans usually work off a hydraulic system. Because of the extensive linkages and bearings used in this design, preventive maintenance is critical. Lack of maintenance can result in calamitous failure which becomes extremely costly. The use of a VFD eliminates the need for complicated linkage arrangements and allows the owner to either replace the fan hub with a fixed pitch design or, in certain cases, the existing variable pitch fan hub can be permanently locked in the max position so that the VFD can be used to vary the air flow.
3. At what size motor does it make more sense to replace than rebuild?
A: Currently, new motor pricing has rendered any motor needing a rewind under 75 HP as a throw away. If the motor is a TEFC as opposed to an Open design, this rating might come down to low as 50 HP. Of course, motors with special physical characteristics and torque configurations can require motors as low as 1 HP to have to be repaired rather than replaced.
4. How do I know if I have an inverter wound motor or do I really need one so I can install VFDs?
A: Manufacturers will make note if their motors are inverter compatible. This means that the motor can withstand the electrical stress exerted on the motor windings by the VFD.
5. What are these Aegis Rings and how to they protect motor bearings?
A: Aegis Rings are mounted on the outside of the motor, up against the motor endbell. It is designed to channel the shaft currents from the motor shaft through the device safely to ground so that the damaging currents do not pass through the bearings themselves. However, almost all motor manufacturers will not install equipment to protect against shaft currents as a standard. This feature is typically special and there is normally an upcharge to have it installed on the new motor.
6. How much variation from the OEM temperature specs can motors tolerate before it becomes a problem?
A: Every 10 degrees of constant operation above the rated insulation temperature reduces the total insulation life by one half.
7. One of our motors has a vibration, how can I tell what is causing it and how serious it is?
A: Vibrations can be caused by many things such as alignment, worn bearings, an uneven base and even its driven load. Testing the motor for these symptoms will tell you what is giving you a problem and how severe it is.
8. I have two older pumps that I think were oversized for the application when they were purchased. How can I tell if they are proper for the service requirements and what can be done to improve their efficiency?
A: Specifying the right pump for a specific application takes a pump engineer to calculate parameters such as flow, static and dynamic head and specific pump curves compared to your system requirements. At that point, a best operating point can be mapped on the pump curve and can be compared to your current operating conditions. If there is a significant difference, we can discuss what options are available.
9. The switchgear for our plant has been in place for years. How can I tell if it will operate as designed if we have an incident?
A: NO ONE BUT A QUALIFIED TECHNICIAN SHOULD ATTEMPT TO WORK ON OR TEST SWITCHGEAR. NETA (National Electrical Testing Association) certified technicians are trained to safely test your switchgear and make repairs as required. Special attention should be paid to arc flash hazards to insure that the proper personal protective equipment is utilized when operating your switchgear.
10. We have several older motors, pre premium efficiency motors, that are running just fine. How can I tell if it makes dollars and cents to replace them with premium efficiency motors?
A: Either your power company or Longo can provide you with hard numbers on what effect such a changeover would have on your operation. There are costs outside of just the power consumption, such as maintenance, etc. that can come into play. Once you can see for yourself the pay back figures, you will be able to make a knowledgeable decision.