Test characteristics of wound rotor three-phase asynchronous motor
The main feature of the wound rotor three-phase asynchronous motor is that its rotor winding can be connected in series with the applied resistor, and the total resistance of the rotor winding loop is changed by changing the resistance of the applied resistor, thereby changing its starting current and starting torque. When the applied resistance is large, the starting current is small and the starting torque is large. According to its characteristics, such motors are mainly used in applications where the power supply capacity is small and high starting torque is required. Because the external resistance of the rotor can be adjusted within a certain range, there are applications in some devices that require a small amount of speed regulation. .
Unique general test items and test methods
● Determination test of stator and rotor voltage ratio
The stator and rotor voltage ratios are an evaluation index given in the technical conditions of the wound rotor three-phase asynchronous motor. The test for determining the stator-to-toror voltage ratio of a wound rotor three-phase asynchronous motor is also referred to as measuring the open-circuit voltage test of the rotor.
(1) Test method. Before the test is energized, in order to prevent the rotor from rotating due to the torque generated by the induced current in the rotor core during energization, the rotor should be blocked by the instrument beforehand. Before blocking the rotor, first turn on the power to see the direction of rotation of the rotor, and then install the jamming device. For smaller capacity motors, higher strength planks can be used to support the keyways of the motor shaft extension.
During the test, the three-phase winding of the rotor was opened. The rated winding voltage U1N of the rated frequency is added to the stator winding. The induced electromotive force generated by the three windings (commonly referred to as rotor line voltages U21, U22, U23) is measured between every two collector rings. When measuring, use a voltmeter and a test pen with insulation requirements, and take care to prevent electric shock.
●Measurement of DC resistance of rotor winding
The three-phase rotor windings of the three-phase wound rotor asynchronous motor are generally connected in a star shape and sealed inside the motor, without drawing a neutral line. Therefore, only three line resistances can be measured outside the motor. If there are no special regulations, measurements should be taken between the three collector rings.
●Measurement of temperature rise of rotor winding
Test method and thermal test for calculating the same stator winding. It should be noted that in the process of measuring the thermal DC resistance during the steady rise of temperature rise, the two resistance measuring instruments connected to the stator and rotor windings cannot repeatedly turn off the respective power sources, otherwise the induced electromotive force will be affected by the windings. measuring.