The stator winding series resistance starting is carried out at the sacrifice of starting torque, and is only suitable for starting under light load or no load. Today, Senli Motor Xiaobian will take you to understand about the rotor series resistance or frequency sensitive resistance starting mode of three-phase asynchronous motor.

       When heavy-duty starting is required, the method of three-phase rotor series symmetrical resistance can be used. wire-woundThree-phase asynchronous motorThe rotor winding is connected to the resistance through a slip ring.

       Generally, the starting resistance is graded into a star shape. When starting, all the starting resistors are connected first. With the progress of starting, the motor speed increases, the rotor starting resistors are shorted successively. Series resistance starting increases rotor resistance and reduces starting current. When suitable rheostat resistance value is selected, rotor power factor and starting torque increase significantly.

       If you want to obtain good starting characteristics, generally need more starting stages, more electrical appliances, complex control lines, large equipment investment, maintenance inconvenience, and due to step by step cutting resistance, will produce a certain mechanical impact. Frequency-sensitive rheostat is widely used in industrial and mining enterprises to control the starting of winding asynchronous three-motor instead of starting resistor.

       Frequency-sensitive rheostat is a kind of non-contact electromagnetic element whose impedance value changes significantly with frequency and is sensitive to frequency. It is essentially a three-phase reactor with a very large core loss. When the motor is started, the frequency sensitive rheostat is connected in series in the rotor winding, because the equivalent impedance of the frequency sensitive rheostat decreases with the decrease of the rotor current frequency, so as to achieve the purpose of automatic rheostat. Therefore, only a first-stage frequency-sensitive rheostat can be used to start the motor smoothly.

       The shortcomings of series frequency sensitive rheostat starting: due to the existence of inductance, the power factor is low, and the starting torque is not large. Only suitable for light load start, not suitable for heavy load start.

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