Motor control

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Most of the "bad press" for magnetic wedges comes from rewind shops, actually. Either the incorrect material is used (ranging from a poor magnetic profile to one that is not magnetic at all), or a bad match regarding mechanical strength is made (shape is wrong, or grain orientation is incorrect leading to poor retention of the coil, or the magnetic properties are damaged by the machining process, etc.)
Altitude Standard motors are designed to operate below 3300 feet. Air is thinner and heat is not dissipated as quickly above 3300 feet. Most motors must be derated for altitude. The following chart gives typical horsepower derating factors, but the derating factor should be checked for each motor. A 50 HP motor operated at 6000 feet, for example, would be derated to 47 HP, providing the 40°C ambient rating is still required.
If a guarantee is involved with stiff liquidated damages, then lots of testing and certification on each serial numbered unit is likely to be necessary. (not to mention the cost of law suits....). Like the supply of a nuclear reactor: the reactor is free, it is the paper work that costs billions.
What motor rating is used is determined by the amount of torque required to move the load. Horsepower does not move the load, torque moves the load. A 1-hp, 6-pole motor will develop 50% more torque than a 1-hp, 4-pole motor If the manufacturer of the agitator is provided with the density of the material beforehand they should determine what torque is required and supply a motor to suit.
The real facts which determine the usability of anti-friction or sleeve bearings: low coast over a long period; cheaper periodic maintenance and/or reduced noise. Another important reason for the application of sleeve bearing is the rotor dynamic design.
Most important is the starting torque of the motor, with the major difference, high starting torque motor or a normal starting torque motor. Depending on the type of load you need to accelerate you will select the motor accordingly. Compressors for example are normally a high starting torque application that will require the high starting torque motor.
Clarke and Park Transformation are "simply" matrix of transformation to convert a system from one base to another one:
- Clarke transform a three phase system into a two phase system in a stationary frame.
- Then Park transforms a two phase system from a stationary frame to a rotating frame.
Which method is better to drive this motor?
Trapezoidal control was discarded because of the ripple that affects motor torque (smooth movement desired). Now, is it sinusoidal control good enough or FOC control? Sinusoidal control has some problems with high rotation speeds, but, what is considered a high rotation speed?
Common mode currents are motor bearing killers. 1) use as low a carrier frequency as the VFD will allow. 2) make sure that one bearing is grounded and the other is insulated 3) use a dv/dt filter 4) make sure that the bearings installed are proper for the load, roller or ball bearings 5) Use an Aegis or Hedwig shaft grounding device.
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service VSD blog: A deep observation of automation control industry, especially in AC motor variable speed drive for industrial motor controls.

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