电动机启动方式

电动机启动方式 By increasing the turn-on angle of the thyristor, the starting current of the motor rises linearly from zero to the set point. (2) constant current starting. The soft starter can introduce the current closed loop control, so that the motor keeps constant current in the starting process, and ensures the smooth starting of the motor. (3) according to the load and the characteristics of the relay protection of the power grid, it can freely stepless adjust to the best starting current. 4. what is the soft parking of the motor? When the motor is shut down, the traditional control methods are completed by instantaneous power failure. But there are many applications that do not allow the motor to be switched off instantaneously. For example: high-rise buildings, building water pump system, if the instantaneous stop, will produce a huge "water hammer" effect, so that pipes, and even pumps were damaged. In order to reduce and prevent "water hammer" effect, it is necessary for the motor to stop gradually, that is, soft parking, and soft starter can meet this requirement. In the pumping station, the application of soft parking technology can avoid the damage of the flap door, reduce the maintenance costs and maintenance workload. The soft stop function of the soft starter is that the thyristor gradually reduces the turn-on angle from the full conduction to the full shutdown after the stop instruction is stopped. Parking time can be adjusted from 0 to 120s in accordance with actual needs. 5. how to realize light load energy saving for soft starter? The squirrel cage induction motor is an inductive load. In operation, the current in the stator coil winding is lagging behind the voltage. For example, when the working voltage of the motor is constant, the power factor is low when the light load is in, and the power factor is high when the load is heavy. The soft starter can be realized in the light load, by reducing the motor terminal voltage, improve the power factor, reduce the electrical copper loss, iron loss, achieve the purpose of energy-saving light load; when the load is heavy, can improve the motor terminal voltage to ensure the normal operation of the motor. What protection functions does the 6. soft starter have? (1) overload protection function: soft starter introduces current control loop, so it can track and change the current of motor at any time. By adding overload current setting and anti time limit control mode, the overload protection function is realized, and when the motor is overloaded, the thyristor is switched off and an alarm signal is sent out. (2) lack of phase protection function: when working, the soft starter detects the change of the three phase current at any time. Once the stop current occurs, the phase protection reaction can be made. (3) overheating protection function: the temperature of the thyristor radiator is detected by the internal thermal relay of the soft starter. Once the radiator temperature exceeds the allowable value, the thyristor is automatically turned off and an alarm signal is sent out. (4) other functions: through the combination of electronic circuits, but also in the system to achieve other kinds of interlocking protection. 7. what is a soft start MCC control cabinet? MCC (Motor, Control, Center) control cabinet, that is the motor control center. MCC soft start control cabinet consists of the following parts: (1) the input end of the circuit breaker (2), soft starter (including electronic control circuit and three-phase thyristor), soft starter bypass contactor (3), (4) two secondary side control circuit (complete the selection and operation of manually starting, remote start soft start and direct start function), voltage and current display and fault operation status indicator. 8. why are soft starters fitted with bypass contactors? Most soft starters have bypass contactor contacts on both sides of the thyristor: (1) the control cabinet has two kinds of starting modes (direct start and soft start). (2) the end of the soft start, bypass contactor is closed, the soft starter is out of operation, until the stop, once again put into, so that prolong the life of the soft starter, but also to avoid network harmonic pollution, but also can reduce the thyristor soft starter in pipe heat loss. 9. what are the extended functions of the soft start MCC control cabinet? The soft start MCC control cabinet can be further assembled so as to realize a plurality of composite functions. For example: the two control cabinet plus control logic, you can form a "one use, one standby" program for the building's fire fighting systems and spray pumps, pumps and other systems. If equipped with PC (programmable logic controller), can achieve the fire pump timing (such as half a month) automatic detection, automatic timing shutdown; the corresponding control logic plus, can the fire pump and the system is functioning properly implement the usual detection, timing of low water pressure (no water) operation; at the time of the fire, the implementation of full load operation. A plurality of motors are combined with a control logic to form a living pump system or other special systems, and each motor is opened successively according to the required quantity, and the motor can be reduced successively to achieve the optimum efficiency operation. Also according to customer requirements, the realization of multiple motors each automatic conversion operation, so that all the motors are in the same operating life. 10. what are the soft starter applications? In principle, squirrel cage induction motors are applicable to various applications where speed regulation is not required. The current range of applications is AC 380V (also 660V), with motor power ranging from several thousand watts to 800kW. Soft starter is especially suitable for all kinds of pump load or fan load, and needs soft starting and soft parking. Similarly, for the variable load condition, the motor is in light load for a long time, only in short or momentary heavy load situation, the application of soft starter (without bypass contactor) has light load energy saving effect. The soft starting of motor mainly adopts the following ways: 1. Lower the power supply voltage to start 2. Lower power frequency start 3. Reduce excitation current start The soft starter mainly adopts silicon controlled phase shift to reduce the motor voltage and realize soft start. The so-called soft start motor, motor starting to slow current is low, so the impact on the grid, at the same time can reduce the load margin of transformer and a control circuit, and improve the service life of the equipment. When the AC motor is started directly, the starting current is 6~10 times of the running current, and the soft start technique is used to reduce the starting current to 1~3 times.