Electric Motor no-load:
generally refers to the electric motor is not connected with the dragged equipment, in the rated voltage, rated frequency conditions of operation.
No-load test is an important item of the electric motor manufacturing factory test, from the motor no-load current and no-load loss, to determine certain performance indicators of the electric motor.
Its essential role is to evaluate the efficiency, power factor, and temperature rise of the electric motor through the correlation between no-load data and load data, and also to check whether there is mechanical stalling and other undesirable conditions of the electric motor.
In order to determine the accuracy of the data, the electric motor should be no-load rotation for a long enough time (generally not less than 30 minutes); no-load state generated losses, mainly core loss, copper loss and mechanical loss.
it is an important component of the electric motor loss, the size of the loss, which directly affects the efficiency level of the motor, no-load loss is large, the corresponding efficiency level is low, conversely, the no-load loss of high-efficiency motors should be relatively small.
For any of the specifications of the electric motor, the no-load loss value should be within an appropriate range, when the loss value exceeds the corresponding range, the cause should be analyzed, especially when the no-load loss increases, the relevant checks should be carried out.
The size of the no-load loss can likewise be judged somewhat from the size of the no-load current, and the specific reasons can be analyzed with reference to the reasons for the large no-load current.
Possible causes include:
(1) Insufficient effective iron length of the electric motor.
Causes of the problem include stator and rotor axial misalignment, core lamination is not solid, core there is a serious horse shoe or pop open, etc.
(2) Motor stator and rotor air gap is greater than normal.
The most common reason for this result is that the rotor diameter is less than the normal value, which occurs in the machining process of the rotor surface.
(3) The material of the electric motor core does not match.
The possible cause is the use of low-grade silicon steel sheet;
for repairing the electric motor, if the winding is reworked, if the original winding is dismantled by incineration, it will largely lead to the deterioration of the magnetization properties of the silicon steel sheet, resulting in increased iron loss.
However, all of the above problems can be found in the factory test stage of the motor, customers in use when the motor no-load current increase, should be analyzed from the mechanical properties, rated voltage, and the electrical properties of the winding.
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single phase motor: YC, YCL with cast iron body and ML , MY motor with Aluminium body
Three phase motor : IE1, IE2, IE3 motor for both cast iron body and Aluminium body
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VFD motor : frequency variable drive motors.
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