Typically there are coils wound on the stator; the rotor is installed and fixed on the base via bearings or bushings. There are silicon steel sheets on the rotor. The rotor of the DC motor will also be wound with coils. they are all in working order. Due to the action of the coil, the current will generate a magnetic field on the silicon steel sheets of the stator and rotor, and the magnetic field will cause the rotor to rotate.
The stator of an asynchronous motor is composed of the stator core, the stator windings and the frame
1 Stator core
The function of the core of the stator is. serve as the motor magnet for the circuit and the built-in stator windings. The stator core is made of 0.5mm thick silicon steel sheets. Both sides of the brick steel sheets are coated with insulating paint to insulate the sheets from each other to reduce the core loss caused byr the rotating magnetic field in the stator core. There are several identical slots drilled into the inner circle of the stator core to integrate the stator windings.
2. Stator Winding
The stator winding is the part of the motor circuit. Its main function is to pass current and generate induced potential to achieve electromechanical energy conversion. The stator winding coils are divided into single-layer and double-layer distribution in the stator location. In order to achieve better electromagnetic performance, ABB medium and large asynchronous motors use short-pitch double-layer windings.
3. Stator Base
The main function of the base is to fix and support the stator core, therefore it must have sufficient mechanical strength and rigidity to withstand operation or transportation. of the motor. Alt current motorsMedium and small sized boats generally use cast iron frames. For larger capacity AC motors, welded frames made of sheet steel are generally used.
The rotor of an asynchronous motor is composed of a rotor core, a rotor winding and a rotating shaft.
1. Rotor core
The rotor core is part of the magnetic circuit of the motor. Together with the stator core and the air gap, it forms the entire magnetic circuit of the motor. The rotor core is generally made of 0.5mm thick silicon steel sheets. Most of the rotor cores of medium and small AC motors are directly installed on the motor shaft. The rotor core of a large AC motor is installed on the rotor bracket, and the bracket is sleeved on the rotating shaft.
2. Rotor winding The function of the rotor winding is to induce an electric potentialthat, to circulate the current and generate an electromagnetic torque. Its structural forms include squirrel cage type and wire wrap type.
1. Squirrel cage rotor
The squirrel cage rotor winding is a self-closing winding. A guide bar is inserted into each rotating slot. At the slots protruding from the two ends of the iron core, two end rings respectively connect the two ends of all the guide bars. A6 If the iron core is removed, the shape of the entire winding looks like a "round cage", so it is called a squirrel cage rotor.
2. Wound rotor
The wound rotor is similar to the fixed winding. It is a three-phase symmetrical winding with insulated wires embedded in the rotor core slot and connected to form a star. Then connect the three small ends of the wire to the three collector rings on the shaft,then draw current out through the brushes. The characteristic of the wound rotor is that it can collect electricity through the rings and brushes are connected to external resistors in the winding circuit to improve the starting performance of the motor or adjust the speed of the motor. In order to reduce brush wear, the wound asynchronous motor is sometimes equipped with a brush lifting short-circuit device, so that when the motor starts and there is no need to adjust the speed, the brushes are raised and all three slip rings are short-circuited at the same time.
What is the maximum allowable generator winding temperature? What temperature of the iron core must not be exceeded?
The structure and block diagram of the generator are as follows:
1. The composition of the generator:
A generator is generalement composed of a stator, a rotor, and a generator is generally composed of a stator, a rotor, a generator end cover, a bearing and other components. The stator consists of the stator core, wire windings, base and other structural parts that secure these parts. The rotor is composed of a rotor core winding, a retaining ring, a center ring, a slip ring, a fan and a rotating shaft.
The stator and rotor of the generator are connected and assembled by the bearings and end covers, so that the rotor can rotate in the stator and carry out the cutting movement of the magnetic lines of force, thus generating an induced effect. electric potential, which is discharged through the terminals and connected to the circuit, an electric current is generated.
2. Generator Working Principle:
Synchronous generator works on the basis ofprinciple of electromagnetic induction. It uses the relative motion of the rotor's magnetic field and. the stator winding. Converts mechanical energy into electrical energy.
When the rotor is driven by an external force, the magnetic field of the rotor and the stator conductor move relative to each other, that is, the conductor cuts the magnetic lines of force, so that an induced electromotive force is generated. in the driver, and its direction can be determined according to the right-hand rule. Since the position of the rotor poles causes the conductors to intersect the magnetic field lines in a vertical direction, the electromotive force induced in the stator winding is then maximum.
When the magnetic pole rotates 90 degrees. The magnetic pole is in a horizontal position, the conductor does not intersect the magnetic field lines and its induced electromotive force is zero. When the rotorurn another 90 degrees, the timing stator winding again cuts the magnetic field lines in the vertical direction, making the induced electromotive force reach the maximum value, but in the opposite direction to the previous one.
When the rotor turns 90 degrees, the induced electromotive force becomes zero again. In this way, the rotor rotates once and the induced emf of the stator winding also changes positively and negatively. If the rotor continues to rotate at a constant speed, a periodically changing alternating electromotive force is induced in the stator winding.
How to check the failure of the stator winding of an alternator
The insulation level of the stator winding and the core of iron of the generator is F, and the maximum temperature should not exceed the temperature limit of 105°C.
During nominal operation of the generator, theThe temperature range of stator winding and iron core is 60℃ to 80℃.
Detailed information:
Generator temperature and warm-up requirements:
1. The bearing outlet oil temperature does not exceed 65°C, and the bearing temperature does not exceed 80°C.℃.
2. The air temperature at the inlet of the generator should not be lower than 20℃, the maximum should not exceed 55℃, and the temperature difference between the two sides should not be greater than 3℃.
3. When the generator inlet air temperature is between +40℃ and +45℃, for every 1℃ increase, the allowable value of stator current will be reduced by 1.5% from the rated value . ?
4. When the inlet air temperature is +45℃, the apparent power of the generator should be reduced by 7.5%.
5. When the temperature ofe inlet air is between +45℃ and +50℃, for every 1℃ increase, the allowable value of stator current is reduced by 2% from the rated value.
6. When the inlet air temperature is between +50℃ and +55℃, the allowable value of stator current is reduced by 3% from the rated value for every 1℃ increase.
7. The maximum air temperature at the generator inlet must not exceed 55°C. If it exceeds, measures must be taken to reduce the active and reactive loads of the generator. If that doesn't work, please. consult the chief engineer.
8. When the generator inlet air temperature is lower than the rated value, the allowed stator current increases by 0.5% from the rated value for every 1°C decrease. is also allowed to increase accordingly, but the generator is only allowed to increase until the tempinlet air temperature is +10% lower than the nominal value. If the intake air temperature drops further, the current value should not increase any further.
9. The air temperature difference between the generator outlet and inlet should generally not be greater than 25°C. If it exceeds 25°C, the cause must be found.
10. Under normal circumstances, the water temperature at the inlet of the air cooler should not exceed 20℃ and should not be lower than 5℃, or the air cooler should not contain condensation.
11. The maximum air temperature at the generator outlet should not exceed 70℃.
Baidu Encyclopedia-Insulation level
1, visual inspection. Use your eyes to check the coils for any abnormally discolored areas.
2. Smell, smell if there is an odor of burnt insulation material.
3. Use instruments to detect the state of isolation between the windings and the iron cores.
4. If necessary, use a precision bridge to measure the DC resistance of the winding to ensure that it conforms to the manual value.
Detailed Information:
Common Causes of Alternator Failures
1. Stator core This is usually the case. made of 035~05mm thick fan-shaped silicon steel sheets, with insulating paint film between the sheets. The side is stacked on the pigeon tail ribs. A number of laminated sheets form an iron core segment, and there are ventilation trenches between them. segments. During generator operation, the stator core must have corresponding mechanical, electrical and magnetic properties. Therefore, the defects of the iron core mainly include: loose iron core; damage to insulation between sheets; La partial loss of teeth and burning of pieces of the iron core;
2. Iron core failure caused by manufacturing and installation quality, etc. 21.1 The quality of steel plates is poor. For example, the thickness of the silicon steel sheet is uneven, there are burrs on the edges, and the paint film quality is poor.
3. The pressing pressure of the iron core is inappropriate. Press fitting of the iron core requires an appropriate pressure range. Insufficient pressure will directly cause the iron core to loosen, cause wear between parts, and damage the core. Destroy the insulation between the sheets. Excessive pressure can damage the insulation between the sheets.
4. Pressure finger, pressure plate pressure deviation or uneven pressure: due to factors such as processing and installation quality, core pressure finger, pressure deviationn of the pressure plate or uneven pressure results in partial loosening of the iron core and end steps. Faults such as tooth falling and parts falling often occur, which can seriously cause the parts of the main insulation of the bar to be worn until the main insulation breaks, causing an accident grounding.