The influence of the no-load current of the motor on the motor
Electric motors are widely used in factories and enterprises. They are electrical equipment that is often in contact with electricians. When the motor is running at no load (without load), the current flowing through the three-phase stator windings is called the motor's no-load current.
The vast majority of the no-load current is used to generate a rotating magnetic field, called the no-load excitation current, which is the reactive current component of the no-load current.
A small part of the no-load current is consumed by various power losses such as friction and core loss when the motor is running at no load. This small part is the active current component, but the proportion is small or even negligible.
Therefore, the no-load current basically does not make a reactive current of useful work. From this point of view, the no-load current should be small so that the motor's power factor is increased. Thus, it plays a role in the energy-saving of the power grid and reduces the maintenance cost of the circuit.
Conversely, if the no-load current is large, since the cross-sectional area of the stator winding is constant, and the current allowed to pass is constant, you can only reduce the active current flowing through the wire, and the load that the motor can drive is When the motor output is reduced, the load is huge, and the winding is prone to heat or even burn the motor.
However, the no-load current should not be too small. Otherwise, it will affect the other performance of the motor, making its performance worse. Therefore, the no-load current of the motor should not be too large or too small. Generally, the no-load current of a small motor is about 35%-50% of the rated current, and the no-load current of the large and medium-sized motor is about 20%-35% of the rated current. It is more appropriate.
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