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LAMINATIONS
The steel portion of the rotor and stator cores made up of a series of thin laminations (sheets) that are stacked and fastened together by cleats, rivets or welds. Laminations are used instead of a solid piece in order to reduce eddy-current losses.
LARGE MOTORS
Usually refers to AC motors in 5,000 series frames and above and to 500 series frames and larger in DC.
LOAD
The burden imposed on a motor by the driven machine. It is often stated as the torque required to overcome the resistance of the machine it drives. Sometimes “load” is synonymous with “required power.”
LOCKED ROTOR CURRENT
Steady-state current is taken from the line with the rotor at standstill (at rated voltage and frequency). This is the current seen when starting the motor and load.
LOCKED ROTOR TORQUE
The minimum torque that a motor will develop at rest for all angular positions of the rotor (with rated voltage applied at a rated frequency).
LOSSES
A motor converts electrical energy into mechanical energy and in so doing, encounters losses. These losses are all the energy that is put into a motor and not transformed into usable power but are converted into heat causing the temperature of the windings and other motor parts to rise.
LUBRICATION
In order to reduce wear and avoid overheating certain motor components require lubricating (application of an oil or grease). The bearings are the major motor component requiring lubrication (as per manufacturer’s instructions). Excess greasing can, however, damage the windings and internal switches, etc. (See PLS)