A three-phase winding of a motor is connected end to end in reverse.
, what happens when you start? How to find it?
Answer: The first-phase winding of the three-phase winding of the motor is reversely connected, then when starting:
(1) Difficulty starting.
(2) One-phase current is large.
(3) Vibration may cause loud sound.
The general way to check me is:
(1) Carefully check the three-phase winding head and Nepal mark.
(2) Check the polarity sequence of the three-phase windings, if it is not N and S staggered distribution, it means that one phase winding is reversely connected.
6
Why can't one phase of the stator winding of the induction motor start?
Answer: For the three-phase star-connected stator winding, when one phase is disconnected, the motor is at the line voltage where only the two-phase line is terminated with the power supply, forming a series circuit.
become single-phase operation.
During single-phase operation, the following phenomena will occur: the original stopped electric motor cannot be started, and it makes a "hmm" sound. Pull the rotor shaft by hand, and it may be able to slow down.
Turn slowly. The speed of the original rotating motor slows down, the current increases, the motor heats up, and even burns out.
7. What are the abnormal phenomena of broken rotor bars during star-type induction motor operation?
Answer: The rotor of the most hall-type induction motor is fresh in operation, the speed of the motor will become slower, the stator current will fluctuate periodically, and the fuselage will vibrate.
movement, possibly with a rhythmic "humming sound.
8.
What are the abnormal phenomena of single-phase grounding in the operation of three-induction motor stator windings?
Answer: For a 380-volt low-voltage motor, it is connected to a neutral and point grounding system. When a single-phase grounding occurs, the current of the grounding phase increases greatly, and the motor
Vibration and abnormal noise occur, the motor heats up, the fuse of the phase may be blown at the beginning, or the winding may be damaged due to overheating.
Bad.
9.
What is the effect of frequency semi-ampere motion on the operation of induction motor?
Answer: When the deviation of the lead is more than 1% of the rated current, the operation of the motor will be changed, which will affect the normal operation of the motor.
When the motor voltage is unstable, the magnetic flux is inversely proportional to the frequency, so the change of the frequency will affect the magnetic flux of the motor.
The starting torque of the motor is inversely proportional to the cube of the frequency, the maximum torque is inversely proportional to the square of the frequency, and the maximum torque is inversely proportional to the square of the frequency.
Therefore, the change of the pre-rate also has an impact on the motor torque.
The change of frequency will also affect the speed and output of the motor, etc.
