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| VS-I electro-hydraulic hybrid system of special synchronous servo drive is synchronous servo drive w |
| Through the series of soft starter is connected between the power supply and the controlled motor, its internal control thyristor conduction angle, so that the motor input voltage from zero to a preset function gradually rise, until the end of starting motor, gives full voltage, namely soft start, soft starting process, the electric machine starting torque increases gradually, speed increase. Soft start is starting the following several ways.
Slope boost soft start: start the most simple, does not have the current closed-loop control, only adjusting the thyristor conduction angle, so that a certain function relation with the time increasing. The drawback is, because do not limit flow, in the starting process of motor, sometimes to produce impulse current to make the thyristor is damaged, a greater impact on the power grid, rarely practical application.
Current ramp start: start mode that is in the initial stage of starting of the motor starting current increases gradually, while maintaining constant current reaches a predetermined value (T1 to T2), until the start. The starting process, the rate of change of current rise is according to the motor load adjustment setting. The current rise rate is large, large starting torque, short starting time. The starting method is the most widely used starting mode, starting is especially suitable for the fan, pump load.
Step: starting, starting with the shortest time, so that the starting current quickly reaches the set value, namely step starting. By adjusting the starting current setting value, which can achieve fast starting effect.
Pulse start: at the start stage, let the thyristor in a very short period of time, with a large current through a period of time after the fall, then according to the original set value increased linearly, even into the constant current start. The starting method, in general the load used, suitable for heavy load and the need to overcome larger static friction starting. Y-q starter, starter, autotransformer reactor starting, starting cage motor traditional decompression. The starting method belong to the class starting, has obvious disadvantages, namely starting two impact current appears in the process.
The soft start and the traditional way of starting the difference is:
1, without shock current. Soft starter when the starter motor, by gradually increasing the thyristor conduction angle, so that the motor starting current rises linearly from zero to the set value.
2, the constant current start. The soft starter can be introduced into the current closed-loop control, keep the motor current during the starting process of motor, to ensure the smooth start. According to the load and the power grid relay protection feature selection, can be freely adjusted to the best starting current. Suitable for heavy load and the need to overcome larger static friction starting.
Dual voltage ramp start: in the process of starting, the output torque of the motor with the voltage increase, providing an initial start voltage Us at startup, Us according to the load can be adjusted, will Us to greater than the static friction torque load, so the load can immediately start to turn. When the output voltage from Us began to rise in a certain slope (slope adjustable), motor accelerating. When the output voltage reaches up to speed the voltage of Ur, the motor is basically reach the rated speed. Soft starter in the starting process of automatic detection of speed, voltage, when the motor reaches the rated speed, the output voltage reaches the rated voltage.
Current limit starting: limit the starting current does not exceed a certain set value is the starting process of motor soft starting mode (Im). The output voltage from zero start growing rapidly, until the output current reaches the current preset limit Im, then the advantage of starting the output current is I this is a small starting current, and can be adjusted according to. Little effect on the grid, it is difficult to know the starting voltage drop, can not make full use of space. | | | author: Published at: 2013/4/28 16:10:00 |  |
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