Electric motors imbalance

Electric motors are susceptible to a variety of forcing functions that cause instability or imbalance. The narrow-bands established to monitor the fundamental and other harmonics of actual running speed are useful in identifying mechanical imbalance, but other indices also should be used. 

Change in the position of the sorption front, which is in the part of the column positioned between electrodes, results in bridge imbalance that is registered by a potentiometer. Divergence of the needle, as a result, breaks the contact and a relay reacts. Resistance is increased if the sorption front has risen. If the front has lowered, resistance is reduced. Response of the electric motor of the proportional pump controlling solution flow in response to such signaling with respect to sorption front... 

The sample in a cell or tube is placed in an aluminium or titanium rotor, which is then driven by an electric motor. Although it is relatively uncommon, these rotors, when placed under high stress, sometimes break into fragments. The rotor chamber on all ultracentrifuges is covered with protective steel armour plate. The drive shaft of the ultracentrifuge is constructed of a flexible material to accomodate any wobble of the rotor due to imbalance of the sample. It is still important to counterbalance samples as carefully as possible. 

Mineral-insulated, metal-sheathed (MIMS) cable is suitable for use in most environments, but it is not so suitable for use where there may be vibration. In an old paint spray booth which predated the Highly Flammable Liquids and Liquefied Petroleum Gases Regulations, a spider-frame-mounted, electrical extractor fan had been positioned at the mouth of the extract duct and connected by MIMS cable. The fan motor was totally enclosed and explosion-protected as the paints used were flammable. The maintenance was poor and paint accumulations were allowed to build up on the fan blades causing an imbalance and vibration. This led to embrittlement of the copper sheath of the cable, which cracked and broke. Then one of the conductors fractured and sparking occurred between the ends. Ignition of the spray started a fire in the paint accumulations on nearby surfaces and the factory was burnt down. 

Energy cost can be minimized in many industrial applications by reducing the additional motor watts loss due to voltage imbalance. Uniform application of sin e-phase loads can ensure proper voltage balance in a plant s electrical distribution system used to supply polj hase motors. 

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