Due to the self-excited effect of the DC motor during short-circuit operation, the armature current will reach a large value, which may damage the motor. In order to ensure the reliable operation of the motor and stable regulation, the DC motor must be short-circuit test, the following in accordance with the provisions of the national standard DC motor test method for DC motor short circuit test introduced.
A short - circuit test method for a motor with a series winding in a generator mode
The motor is connected to the reverse direction (differential excitation). The polarity of the sensor is checked by the induction method. When the motor is stationary, the main pole winding is switched on and off, and the excitation current (not exceeding 20% of the rated value) is switched off. The induction voltage is measured at both ends of the series winding with a DC voltmeter The polarity of the potential, such as in the excitation current instantaneous excitation winding in the induced potential of the voltmeter positive deflection, then the main pole connected to the power supply positive and the series winding voltage meter in the positive side of the same Sex.
The test motor according to the no-load generator mode, the polarity of the excitation power and the same before, with a voltmeter to measure the polarity of the voltage across the armature, and then stop the positive side of the series and no-load generator voltage negative End connected, then the series winding is reverse access.
Second, in the generator mode with a power amplifier to control the excitation of the short circuit test method
Ak1 - control windings, amplifiers of the main excitation winding; Ak2 - control winding, due to the expansion of the remanence of the magnetic circuit is high, to reduce its remanence; Ak3 - control winding, to suppress the role of self-excitation
In the generator mode with the power amplifier to control the excitation of the short circuit method test schematic diagram shown in Figure 2, according to Figure 2 shown in the load test R4 should be shorted.
If there is no power amplifier, can be replaced with a compound DC generator, the series winding instead of Ak3, then into a complex excitation, or with two series (the opposite direction of the potential) of the exciter for the test motor excitation.
Short - circuit Test Method for Three Temporary Winding Crossover Windings
In the main pole on a temporary winding a series winding, the polarity is still determined by induction.
Four half of the main pole winding reverse short circuit test method
(In order to prevent the remanence voltage to make the generator short-circuit when the impact current is too large, the excitation method should be opposite to the direction of remanence), and the other is the same as the remanence A group is connected in parallel at both ends of the armature.