Why does the motor choose a magnetic wedge?
The motor slot wedge mainly includes 3240 epoxy cloth plate wedge, lead groove wedge, magnetic groove wedge, silicone groove wedge, 4330 molded groove wedge and diphenyl ether groove wedge, etc. Among them, the magnetic groove wedge is special and widely used. On high voltage or high efficiency motors. Today, Ms. will talk to you about the characteristics of magnetic wedges.
Magnetic wedge and motor loss
The magnetic wedge can be magnetically guided as literally. The magnetic flux wedge can be formed by adding a magnetic conductive material (such as a magnetic conductive metal material such as steel wire, steel sheet, or iron powder) to the material of the wedge.
An asynchronous motor is an electromechanical conversion device that converts electrical energy into mechanical energy, causing losses during the conversion process. These loss ratio relationships are related to motor capacity, type, pole number, etc.: mechanical losses of the motor with a small number of poles (high speed) account for a large proportion, and the no-load stray loss increases with the number of poles of the motor, and the load stray loss The number of poles of the motor increases and decreases.
The motor does not have a load, and the motor's iron loss measured at the rated voltage and rated frequency is applied to the motor, which is called no-load iron loss. It consists of base wood loss and additional iron loss. The basic iron loss is mainly the hysteresis eddy current loss generated by the main magnetic flux in the stator core teeth and in the stator turns. Since the rotor frequency is extremely low during normal operation of the motor, the hysteresis and eddy current losses caused by the main magnetic flux in the rotor are negligible.
The no-load additional iron loss is generated in the stator and rotor core by the harmonic flux caused by the cogging effect in the motor. The high frequency additional iron loss induced by the stator and rotor in the core is called the pulse vibration loss. Further, the stator and the rotor tooth portions are sometimes aligned and sometimes shifted, and the tooth surface of the tooth surface is changed, and eddy current can be induced in the tooth surface line layer to cause surface loss.
Test data statistics, pulse vibration loss and surface loss are called high frequency additional loss, they account for 70~90% of motor stray loss, and the other 10~30% is called load additional loss, which is generated by leakage flux.
Magnetic wedges are used to reduce losses
The use of magnetic wedges reduces surface loss and pulse loss, and surface loss and pulse loss are the main losses in no-load iron losses. The larger the width of the motor slot, the smaller the average length of the air gap and the greater the surface loss. The pulse amplitude value of the air gap magnetic density using the magnetic slot wedge is significantly reduced, so the motor surface loss is reduced. In addition, since a part of the magnetic flux passes through the magnetic slot wedge, the magnetic density in the teeth is reduced, and the pulse vibration loss is also reduced.
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