Installation
by BALJEET VASEER
Installation should be carried out by qualified and experienced personnel. The following points should be noted before installation and commissioning of motors:- The motor foundation must rigidly support all four feet of the motor in the same plane. Shims should be placed under the motor feet, as required, so they will not be pulled out of plane when mounting bolts are tightened.
All wiring to the motor and control must be in accordance with the Electricity codes Before energizing the motor, inspect and tighten all covers, hardware and accessories, which may have become loosened during transport and handling.
Turn the shaft of the motor by hand to be sure that it rotates freely.
If the motor has been mishandled sufficiently to break external parts, the end shields should also be removed to check for internal damage, unless the motor is explosion proof.
Examine the outside of the motor carefully for damage with particular attention to conduit box, fans, and covers. Energize the motor momentarily to check that the direction of rotation is proper. For direct connected loads accurate alignment should be carried out. Any change in shims, requires rechecking alignment. When installing V-belt sheave, spur or helical pinion or chain drives, be certain that they are within the Indian standard specifications.
OPERATION BEFFORE COMMISSIONING: 1) It is important to note that repeated trial starts can overheat the motor and result in motor burnout. If repeated trial starts are made, allow sufficient time between trials to permit heat to dissipate from windings and rotor to prevent overheating. Starting currents are several times running currents, and heating varies as the square of the current. 2) After the installation is complete, but before motor is put into regular service, make an initial start as follows:-
a) Check motor connections against wiring diagrams. b) Check voltage, phase, and all load drive parameters against motor name plate. c) Special consideration must be paid to ensure that the motor is operating within recommended guidelines. For torque and speed for the type and size of motors being commissioned. d) Under no circumstances should the motor be operated at speeds beyond the safe mechanical limits. e) If load is disconnected, run motor at no load long enough to be certain that no unusual conditions develop. Listen and feel for excessive noise, vibration, clicking or pounding. If present stop motor immediately, investigate the cause and correct before putting motor in service. f) If load is not disconnected, interrupt the starting cycle after motor has decelerated to a slow speed. Carefully observe for unusual conditions as motor coasts to a stop. g) When checks are satisfactory, operate at a minimum load and look for unusual conditions. Increase load slowly to a maximum. Check motor for satisfactory operation. h) Electric motors operating under normal conditions become quite warm. Although some places may feel too hot to touch, the unit may be within temperature rise limits. Use a thermocouple to measure winding temperature when there is any doubt. i) Insulation resistance of the stator and rotor windings should be checked before commissioning, both between the windings and between each winding and earth. This insulation resistance at 75oC should not be less than the value calculated by the formula:-
Insulation resistance in mega ohms = R = rated voltage in volts 100 rated power of motor in KW 100
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