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Experts

Motors and Drives

Tom Bishop, P.E., is a technical support specialist with Electrical Apparatus Service Association (EASA), St. Louis, Mo. He joined EASA’s staff in 2002 after having had over 30 years of hands-on and engineering experience at electrical machinery manufacturing and service firms. He is a graduate of the New Jersey Institute of Technology with a BSEE. He has authored dozens of technical articles and papers and frequently gives seminars and other talks about rotating electrical apparatus.

Chuck Yung is a technical support specialist for EASA. He worked in the electrical machinery repair industry for 25 years before joining EASA’s staff in 1998. He received his BBA from the University of Houston He is the author of more than 75 technical articles and papers. In addition, he frequently lectures on technical topics.

How can I avoid smoking the motor at startup?
I have a 12.25-inch disk when loaded with components equals about 8 pounds. Others in the same field have a problem of smoking the motor during startup. I want to run at a variable speed to 3600 rpm.

It is important to keep the motor as small as possible, and long life and extremely low maintenance are important.
Category: Motors Drives

How can we increase the speed of an electric motor?
How can we increase the speed of an electric motor by a VFD system supplying energy to a pump? Suppose the motor power is sufficient enough to prevent overloading the motor?
Category: Motors Drives

What would be the power of 2950 rpm-VFD drive to yield 3650 rpm 90 kW output?
I need to supply 90 kW power and 3650 rpm for running a pump. The highest available electric motor would be 2950 rpm. I have to use a variable frequency drive (VFD)-motor system for raising the speed. What would be the power of 2950 rpm-VFD drive to yield 3650 rpm 90 kW output for the pump?
Category: Motors Drives

How do you correctly test the motor after repairing or overhauling?
How do you correctly test the motor after repairing or overhauling? Is there any fixed procedure for taking measurement value? When testing without load, everything is OK. But when I put the load/taking online with rotating equipment (example: pump), it becomes trip overload. Why did this happen?
Category: Motors Drives

How can I connect a new motor to same old motor connection?
I have a pump motor start 660 run 380 volts and power supply is 380 and control for 380. If I purchase a new pump motor 380 start run 220 volts in panel there is timer and two contactor how can I connect new motor to same old motor connection?
Category: Motors Drives

Formula For Selecting A Motor
I want to select a motor for a 120T/hr screw conveyor. Please help with the formula and other requirements.
Category: Motors Drives

How To Calculate Pump Horsepower
If I know the available head of tank or the depth of tank from which some chemical is to be pumped at some particular distance (let’s suppose 1km) and the pipe diameter is 10 inches, then how do I select the adequate horsepower motor for optimum performance? The pump is centrifugal and the flow rate is known.
Category: Motors Drives

High efficiency motor ratings
On premium efficiency motors, the FLA is higher on IEEE841 motors than on standard high efficiency motors. Yet the efficiency is higher on 841. More amps is more watts. What makes a premium efficiency motor more efficient? I'm looking at a 50-hp, 1,800, 3/60/460 motor; (a) 841 motor, FLA: 59.9, Efficiency: 94.5% and a (b) High efficiency motor, FLA: 55.9, Efficiency: 93.6%.
Category: Motors Drives

Pump shaft size and driver relation
What would a general rule of thumb be for pump shaft size related to driver horsepower? I have used the following rule: The minimum pump shaft diameter would be 1 in. for every 100 hp. The minimum pump shaft for a 300 hp driver would be 3 in. to avoid shaft issues. This seems to indicate when a mismatch may occur. Is there another rule of thumb to use that may be better at indicating potential pump issues?
Category: Motors Drives

Partial discharges, condition monitoring
Considering partial discharges related to condition monitoring in electrical equipment: On which type of equipment is this technology applied?; What are the parameters monitored?; What are the equipments/sensors used to monitor partial discharges?; What about indicators/statistics of that monitoring?
Category: Motors Drives

Motor horsepower equation
I have to select a motor for a mixing tank. The tank is 7-ft in diameter and 4-ft high. Two-thirds of the tank will be filled with polymer slurry. I expect the impeller diameter to be 3 ft with a rotational speed of about 300 rpm. Can you please tell me how to calculate the horsepower requirement of the motor? I would appreciate if you could quote a formula.
Category: Motors Drives