The test is carried out when the engine is empty. Except for the following provisions, the external voltage (motor) or induced electromotive force (generator) during the test is 130% of the rated voltage. For synchronous motors whose no-load voltage exceeds 130% of the rated voltage at rated excitation current, the test voltage should be the no-load voltage at rated excitation current, the test voltage of hydroelectric generators should be equal to 150% of the nominal voltage; tension ; for DC motors with four or more poles, the voltage between adjacent collector slices should not exceed 24V during testing; For three-phase wound rotor asynchronous motors (except large 2 and 4 pole motors) and alternating current collector motors, the test must be carried out when the rotor is stopped and in open circuit. Except for the following motors, the short voltage rise time term is 3 minutes; for hydrogenerators and steam turbine generators, the test time for single-turn coils is 1 minute, for multi-turn coils, the test time is 5 minutes; ; for turbogenerators with windings of 130% nominal. For motors whose no-load current exceeds the rated live current, the test time can be reduced by 1 minute. When the test voltage is increased to 130% of the rated voltage, the frequency and speed can be increased at the same time, but they shall not exceed 115% of the rated speed or the speed specified in the test overspeed. For generators with relatively saturated magnetic circuits, when the speed increases up to 115% and the excitation current has increased to the allowable limit, if the induced voltage still cannot reach the specified test voltage , the test can be carried out at the highest possible voltage. .
The specific test steps are as follows: (1) Disconnect the generator output oil circuit breaker. (2) Start the generator and leave it unchanged after reaching the rated speed. (3) Close the excitation switch, then gradually adjust the resistance Rn to increase the excitation current. At this time, the terminal voltage Vo also increases until the terminal voltage reaches approximately 1.25 times the rated voltage. When setting Rn, 9 to 10 points should be selected, and Vo, Il and the corresponding rotation speed should be recorded at multiple points at the same time. Pay attention to the number of points that should be close to the face value. (4) Adjust the resistance Rn to reduce the excitation current until it reaches zero, and record the corresponding Vo and Il values according to each point in (3). When the excitation current falls to zero, the value of the voltageResidual magnetization ion should be read. . (5) According to the recorded Vo and Il values, the general ascending curve and descending curve can be drawn, and then the average value can be obtained to obtain the no-load performance curve of the generator.