How is the temperature resistance of insulating materials divided?
Answer: my country is now divided into six levels, but A.E, B, F, H.C.
(1) The maximum allowable working temperature of Class A insulating material is 105°C
<2) The maximum allowable working temperature of the three-level insulating material is 120c
(3) The maximum allowable working temperature of Class B insulating material is 130C
(4) Class F insulating material has a maximum working temperature of 1559
(5) The maximum allowable working temperature of sheet-level insulating material is 180°C
(6) The maximum allowable working temperature of Class C insulating material is above 180°C
2.
Briefly describe the structure and working principle of induction motor.
Answer: The working principle of the induction motor is like this, when the three-phase stator winding passes through the three-phase symmetrical alternating current, a rotating magnetic field is generated,
This rotating magnetic field de-rotates in the stator, and its magnetic field lines cut the number lines on the rotor, inducing currents in the rotor wires. Mounted on the stator magnetic field and
The rotor current interaction force produces an electromagnetic torque, and the rotating magnetic field of the stator rotates the rotor with the current-carrying wires.
3
-Why is the current large when the induction train starts? And after starting the current public security is small?
Answer: When the induction motor is in a stopped state, from the perspective of the electromagnetic angle, it is a musical instrument, and the stator winding connected to the power supply is equivalent to a transformer
The primary coil, the closed-circuit rotor winding is equivalent to the tertiary line where the sub-voltage transformer is short-circuited; there is no electrical connection between the stator winding and the rotor winding
There is only a magnetic connection, and the magnetic flux forms a closed circuit through the stator, air gap, and rotor core. When the switch is closed, the rotor has not yet rotated due to inertia, and the rotating magnetic field is
Maximum cutting speed one
A synchronous speed cuts the rotor winding, so that the rotor winding induces the highest potential that can be reached. Therefore, at the rotor number
A large current flows through the body, and this current generates magnetic energy that cancels the field of the stator, just like the secondary acid pass of the alternator needs to cancel the effect of a magnetic encounter.
Sample.
In order to maintain the original magnetic flux that is compatible with the power supply voltage at that time, the stator automatically increases the current. Because the current of the technology is very large at this time, it is necessary to
The current also increases very much, up to 4-7 times of the rated current, which is the general reason for the starting current.
Why is it small after starting: With the increase of the motor speed, the cutting speed of the stator magnetic field is smaller than that of the sub-body, and the induced potential in the conductor of the transfer hall is smaller;
The current in the rotor conductor is also small, and the part of the current in the stator current that is used to cancel the influence of the magnetic flux generated by the rotor current is also reduced.
Therefore, the stator sink is from large to small until it is normal.
