Testing the brushless DC motor test, mainly introduces the structure, principle, parameters and performance of the motor; and briefly introduces several commonly used measurement methods.
1: Overview of brushless DC motors DC brushed and brushless are relative, as can be seen from the name. Brushed means that the armature windings are connected in a star shape through resistance, while the brushless motor does not have such a coil, which directly connects the stator poles to the rotor poles.
Since there is no coil, there is no loss problem. Brushless DC motors fall into two categories:
One type is series excitation and the other type is parallel excitation type. The series type is characterized by high rotor speed but low power; the parallel type is characterized in that it can obtain greater power but the rotor speed is generally lower than 3000r/min.
Two: motor structure and working principle:
1. The working principle of the motor The basic working process of the DC motor is as follows:
(1) Before power-on, discharge through a startup capacitor c1 to reduce the voltage across the capacitor to below zero potential.
(2) The starting capacitor c2 supplies power to the rotor excitation winding in the charged state to form a rotating magnetic field.
(3) The rotor rotates.
(4) The current in the main circuit flows through the commutator to achieve commutation.
(5) The large-capacity filter capacitor in the stator plays the role of smoothing the current.
(6) The rectifier bridge rectifies the output power.
(7) The output voltage becomes a pulsating voltage with a higher frequency after inversion.
(8) The pulsating voltage is applied to the terminals of the load.
Three: the basic parameters and detection of the motor:
1. Rated value.
2. Efficiency.
3. Rated output power.
4. Maximum continuous running time.
5. Maximum ambient temperature.
6. The highest ambient humidity.
7. Insulation resistance.
8. Leakage current.
9. Temperature rise.
Fourth, the commonly used measurement methods:
1. No-load test method The voltage value and current value of each point are measured at no-load, and the deviation from the standard value should be less than ±5%.
2. Short-circuit inspection method The method of short-circuiting any two or more points under specified conditions to determine whether the armature winding of the motor under test is short-circuited is called short-circuit inspection method.
(1) Use the ohm gear of the multimeter to take the resistance value between the measured points as normal;
(2) When the resistance value at a certain point is found to be infinite, it means that the number of turns at that point is infinite.
(3) When the resistance value at a certain point is found to be 0 or close to 0, it means that there are few or no turns at that point.
(4) If there is a disconnection of a certain phase, the test piece should be connected to the position of the disconnection of this phase and tested again;
(5) For the three-phase squirrel-cage induction motor using the auto-voltage regulator, the measurement between each phase and the ground and each phase should also be performed at the same time.
