A motor is a machine that uses the interaction between the magnetic field in its windings and the electric current to generate forces in the motor, which convert electrical energy into mechanical energy. If we do reverse this process, then the mechanical energy is converted into electrical energy, which is done by the generator. Electromagnetism is the main phenomenon used in electric motors.
The ratio of the output of a motor to its input is called efficiency and is expressed by the symbol "η". This is the factor that describes the performance of the motor. It is the ratio between the output power and the input power on the shaft and can be written as:
Motor efficiency = motor output power / motor input power
or efficiency = η = output / output + losses.
There is no such thing as a machine without losses. Therefore, the output value of a machine is always less than the input value.
Electric motors incur losses during the conversion of electrical energy into mechanical energy, including resistive losses, mechanical losses due to friction, losses due to the dissipation of magnetic energy in the core and different losses depending on the type of material used. The following are some methods or techniques that can be used to improve the efficiency factor of a motor.
The function of the motor frame is to provide mechanical protection for the windings. It is also responsible for the interface through which the feet are mounted. The motor frame plays a vital role in its thermal performance as it is responsible for transferring the heat generated inside the motor to the surface of the frame where the air blown by the fan will promote heat dissipation. This will reduce heat loss.
The stator, which is the main component of a synchronous motor, is responsible for 60% of the losses, so to reduce these losses the mass of the stator winding must be kept large, as the increase in mass will reduce the resistance. High efficiency motors contain 25% extra copper compared to motors designed for standard efficiency models.
Rotor losses are also considered to be a secondary source of losses caused primarily by the degree of slip displayed by the motor. In order to reduce these losses, the slip must be reduced, which is achieved by increasing the electrical conductivity of the rotor. Copper must be used in large quantities because of its high electrical conductivity. But the copper must be die-cast, as processes have recently been developed for die-casting copper.
The lubrication interval is a function of the rated speed of the motor installation, the bearing size, the type of grease and the temperature rise. Therefore care must be taken when applying the lubricant. Do not mix grease types, even if they use the same elements. If another type of grease is used in the application, this will directly affect the performance of the PM motor.
Reduce the effect of hysteresis and saturated steel by using steel with a small amount of silicon in the laminations instead of low cost carbon steel. In this way, core losses can be eliminated. Flux density and core losses can be minimised by reducing laminations thickness and increasing laminations length.
ZCL GROUP sells a wide range of motors, including synchronous motors, asynchronous motors, permanent magnet motors etc. If you have a requirement please send us a message.
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