First, what is the soft start of the motor? Dalan Motor tells you!
During the starting process of the motor, a specific device is inserted into the stator circuit of the motor, so that the voltage of the motor terminal is gradually increased from small to large to a full pressure within a certain period of time, thereby realizing the starting process of the motor.
Second, the benefits of soft start
1. Reduce the starting current of the motor, reduce the voltage drop of the grid, and reduce the cost.
2. Reduce the torque shock of the motor and the impact on the speed of the load equipment, and prolong the service life of the motor load equipment.
Third, the development process of soft start
Soft start is a soft start device that gradually develops from the earliest solid state autotransformer and reactor to liquid water resistance and thermal resistance and then to solid state thyristor, magnetron, reduction and frequency conversion.
Fourth, the water resistance soft start
1, working principle
a. Winding asynchronous motor: a water resistance soft start device is connected in the rotor circuit of the wound motor. During the starting process of the motor, the distance between the two plates in the resistive liquid is uniformly changed to make the resistance value from large to small. The electrodeless reduction causes the terminal voltage of the motor to gradually increase from small to large to full pressure, thereby realizing the starting process of the motor.
b. Synchronous motor, squirrel cage asynchronous motor, water resistance soft start device is connected in the stator circuit of synchronous motor and squirrel cage asynchronous motor, and the distance between the two plates in the resistance liquid is uniformly changed during the starting process of the motor. The resistance value is reduced from large to small, so that the terminal voltage of the motor is gradually increased from small to large to full pressure, and the starting process of the motor is realized.
2, disadvantages
a. Poor safety; the water resistance box of the device is welded. Long-term use will lead to corrosion and aging, resulting in serious safety hazards caused by leakage of the resistor fluid.
b. Maintenance troubles; the temperature of the resistor liquid will rise and evaporate during the starting process of the motor. It is necessary to add water regularly to replenish the resistor fluid, and the maintenance amount is large. At the same time, the steam generated will also affect the high-voltage lines, posing a safety hazard.
c. The controllable adjustability is poor; the adjustment of the starting current is realized by changing the concentration of the resistive liquid and the initial distance between the two plates, which is very troublesome.
d, poor start stability; water resistance is greatly affected by the ambient temperature, resulting in different starting performance before and after.
Five, thyristor solid state soft start
1, working principle
The trigger pulse is issued by the trigger screen to control the conduction angle of the thyristor, and the conduction angle is adjusted to gradually increase the voltage of the motor terminal from small to large to a full pressure within a certain period of time to realize the starting process of the motor.
2. Disadvantages: a. Low safety and reliability; during the startup process, a large number of series-parallel thyristors are subject to individual differences due to temperature changes, so that the current sharing and voltage equalization will cause individual thyristors to burn and have low reliability. At the same time, low voltage triggering high voltage will cause the trigger board to be broken down and the safety is low. b. The maintenance cost is high; during the use process, the thyristor is often burned, and the large replacement of the thyristor increases the maintenance cost. c. Harmonic pollution is serious; the high-order harmonics generated by the thyristor during the chopper process will have a serious impact on the power grid.
Sixth, solid state magnetic control soft start
1, working principle
In the stator circuit of the motor, a magnetron reactor whose impedance can be changed smoothly is connected. By controlling the magnitude of the direct current in the winding, the impedance of the magnetron reactor is gradually reduced from large to small in a certain period of time, so that the voltage of the motor terminal is reduced. From small to large, gradually increase to full pressure to achieve the starting process of the motor.
2. Advantages: a. Safe and controllable; no hidden troubles. b, good start stability; not affected by ambient temperature. c. Controllable adjustability is good; the startup parameters are directly set through the man-machine interface, and the starting current is arbitrarily selected between 1.5Ie and 4.5Ie, and the adjustment is simple. d, maintenance-free; e, no harmonic pollution; set up a special filter winding to filter out the higher harmonics generated by the magnetron reactor. f, basically no magnetic leakage; set a special closed magnetic channel, so that the alternating magnetic field generated by the alternating current forms a closed loop in the magnetic channel, and the leakage magnetic flux is controlled within 1%.
Seven, self-excited magnetic control compared to the other excitation type magnetic control:
1. The tight coupling structure of each of the AC windings with DC windings is adopted, which increases the adjustment range of the magnetron reactor.
2. Self-excited magnetic saturation technology, self-excited DC current regulation impedance, no need to provide large-capacity low-voltage power supply.
----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant
Copyright http: / (Dalan Motor) Reprint, please indicate the source
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