The starter is divided into manual and automatic according to the operation mode. AC motor manual starter in the more commonly used star - triangular starter, it belongs to the buck starting mode. At start-up, the alternating current three-phase motor winding connected to the star, Jump Starter so that each phase of the winding voltage is reduced to phase voltage to reduce the impact of the starting current.
The starting of the motor is an important part of the motor control, to improve the starting performance of the motor is a continuous research and discussion of a problem, Jump Starter and continue to achieve new results.
The start-up mode of the motor can be divided into full-voltage start (ie, direct start) and buck start.
Full pressure start is one of the simplest starting methods. Start, the entire power supply voltage directly to the motor stator winding, when the starting current is large, up to 5 to 8 times the rated current. Often start the motor, too much starting current will cause the motor heat, affecting the motor life; while the motor winding in the role of electric power, will be deformed, may cause a short circuit and burn the motor; Jump Starter too large starting current, will make the line The voltage drop increases, resulting in a significant decrease in the grid voltage and the operation of other motors connected to the same grid, and sometimes even stopping them or failing to work properly.
"Civil Building Electrical Code" in the provisions of 10,2,1,5: "by the public low-voltage network power supply, the capacity of 11kW and below, can be full pressure start; by the residential substation low-voltage power supply device, The capacity of 15kW and below can be full pressure start. Jump Starter Capacity greater than the above provisions, it should be used to start the buck.
The traditional step-down starting mode is the autotransformer step-down start, the star delta tripping step-down start, the Yanbian triangular step-down start. However, these starting methods have their own advantages and disadvantages, and each way the structure of the motor, the nature of the load has its special requirements, so the practical application of many restrictions. Jump Starter Thus the soft starter came into being. Commonly used soft starter and digital control and two kinds of in this only talk about starter.
1, the working principle of the starter and the characteristics of the squirrel-cage motor soft start technology, successfully solved the AC motor start caused by the larger starting current on the supply voltage quality and power supply line power consumption and the impact of mechanical equipment And other issues. Currently widely used is the full starter. It is the traditional Y-△ start, autotransformer start, Yanbian triangle start ideal replacement products.
Starter is the use of SCR power module dual microcontroller for the control of the core of the new motor starting device, its working principle is as follows:
Three pairs of anti-parallel thyristor in series with the motor on the three-phase power supply circuit, the use of thyristor electronic switching characteristics, by controlling the size of its voltage to achieve the control of the motor soft start process. When the motor starts to complete and reach the rated voltage, Jump Starter three-phase bypass contactor KM pull, so that the motor directly cast network operation. As a result of dual-chip control, according to the load characteristics of any set of various starting parameters, it has a strong load adaptability.
1.1, start mode
The more common starting mode is current limiting type, voltage ramp start mode, torque control type and so on.
1.1.1, current limit type
Can make the motor at the start of the maximum does not exceed the pre-set current limit Im, Im can be based on the user's network capacity and motor load conditions. The setting range of this value is between 1.5 and 5.0 times the motor rated current Ie.
1.1.2, voltage ramp start mode
Voltage ramp start mode is to set the motor input voltage rise rate to complete the motor starting process. Since the voltage from the initial value to the rated value is a linear change (the initial value can guarantee the maximum starting torque of the motor), Jump Starter so the whole start-up process to ensure a smooth start of the motor. The setting range of this value is between 30% and 80% of the motor rated voltage Ue.
1.1.3, torque control type
By controlling the starting torque, the starting characteristics of the motor are improved, the surge torque is cleared and the inrush current is reduced.
1.2, parking mode
(1) free parking: by load inertia free parking;
(2) soft stop: in some cases, do not want the motor suddenly stopped, such as pumps, if the sudden stop, there will be water hanging phenomenon, and then as the industrial belt machine, lifts do not want to suddenly stop. With the soft stop mode, when the shutdown signal is issued, the motor terminal voltage is gradually reduced to achieve the purpose of soft stop.
1.3, the characteristics of soft starters
Soft starter due to the use of computer technology, more traditional way of starting the unmatched advantages:
(1) 16-bit single-chip all-digital automatic control, flexible and diverse control;
(2) starting torque current, voltage, Jump Starter time can be set according to different flexibility, to obtain the best current impact and the best torque control characteristics;
(3) provides a smooth and gradual start-up process for the motor, reducing the impact of the starting current on the grid, reducing the vibration and noise of the equipment, extending the service life of the mechanical transmission system and improving the worker's working environment.
(4) Convenient external control interface has a variety of functions: digital delay start control, soft stop control input, start delay relay output, fault relay output;
(5) with a comprehensive LED display, friendly man-machine dialogue interface, green environment-friendly control unit, power range covering 5.5kW ~ 800kW, can be widely used.
2 starter application
As the soft starter has many advantages, has recently been more and more widely used in the application of civil buildings are also more and more. In general, as long as the motor capacity is greater than or equal to 11kW, in order to ensure that the building of other load power quality, you can use soft starter. With the digital soft starter as the core, supplemented by input circuit breaker, soft starter bypass contactor, and the secondary circuit composed of motor control cabinet, you can complete the two control, a variety of control options. In addition, can display current, voltage and fault operation, working status and other signals.