The company supplies Atlas, Ingersoll Rand, Fu Sheng, Kobelco Sullair, Hitachi air compressor filter (computer controller, computer monitors, computer monitors, computer boards, computer control panel air filter, oil filter, oil separator), air compressor parts, air compressor oil, air compressor lubricants, compressor oil, air compressor supplies air compressor sales maintenance 
 ? Voltage soft starter on the load of the compressor design applications 
 ?. Introduction 
 AC induction motor with its simple structure, high operational reliability, a strong environmental adaptability and excellent drag performance in the field of coal, oil, chemicals, iron and steel, power generation, water, cement and building materials, a wide range of applications . But the fatal flaw of the AC induction motor starting impact, would be adversely affected. Main impact is reflected in two aspects: 
 (1) electrical issues: 
 Start up to 5-7 times the rated current, resulting in the motor winding currents caused by temperature, thus speeding up the insulation aging, causing the voltage fluctuation of the supply network, affecting the normal operation of other devices with the power grid. 
 (2) mechanical problems: 
 Too large starting torque of a mechanical shock, driven equipment caused by the large impact, and shorten the service life, the loss of accuracy. Such as the coupling to damage the belt tear. Caused by normal wear and tear and impact of non-mechanical transmission components, accelerated aging, shortened life expectancy to increase the maintenance workload. 
 Encountered this problem, Shougang cold rolling plant nitrogen production line air compressor motor power (10KV/3730KW and 10KV/2250KW), the first in the process of starting the motor and compressor mechanical shock is relatively large, increased the workload for system maintenance; followed by motor direct starting grid drop more serious in the power grid voltage drop to 85% when other equipment will not work. For these reasons the decision to use PowerEasy SCR soft start device. 
 Two. Thyristors in series composition and principles of the high-voltage soft starter 
 2.1 main loop constitutes 
 Thyristors in series soft starter device is a combination of power electronics technology, optical technology, control technology and micro-processing technology and intelligent design of the all-digital starting equipment. Thyristors in series soft starter wiring diagram of the main circuit as shown in Figure 1, mainly composed of high-voltage thyristor series valve and the bypass contactor, in which the high-voltage thyristor series valve block is the power to transform implementation of the components by more than SCR series and parallel composition, supplemented by absorption, pressure clamp circuit to ensure its reliability in the high-pressure environment. When the line side is energized, to achieve by controlling the conduction angle of SCR chopper, AC three-phase power to control the amplitude of the output voltage. And start the process of completion, will bypass contactor is closed, the soft-start device is switched to the bypass state, at the same time turn off thyristor. 

 2.2.1 the main control circuit 
 The main control circuit of the main DSP microprocessor and CPLD large-scale gate array, digital circuit, its main function is to generate the pulse command triggered thyristor, thyristor trigger command issued by the digital signal processor (DSP). The main control circuit can be collected according to the signal acquisition circuit voltage and current signals to adjust the thyristor conduction angle, so as to adjust the motor current, motor closed-loop control, limiting start. It can issue a trigger pulse at the same time the voltage and current temperature feedback signal monitors the motor and soft start device operating status, protecting the entire system to ensure the safe operation of the system. 
 2.2.2 The trigger system 
 The trigger system is the system stable and reliable key part must have the ability of anti-noise, timely and accurate turn-SCR. There are two major technical problems here: 
 A. Timely and accurate trigger pulse to trigger the thyristor 
 The thyristor is a current-controlled bipolar semiconductor components, it requires that the gate drive unit similar to a current source, provide a particularly steep peak current pulse to the thyristor, to ensure that at any moment, be able to accurately and reliably trigger thyristor. SCR gate trigger pulse characteristics of a very strong influence on the normal work of the thyristor. 
 Thyristors used in tandem, we ask each other series of thyristor as much as possible with the conduction, the opening of the slower may be subject to over-voltage damage to the components, when asked the same series of thyristor opening time difference as small as possible. 
 Thyristor opening speed and the gate trigger pulse amplitude and pulse rising edge of the steepness of the relationship. Means that the larger the gate trigger pulse amplitude, pulse rising edge, the steeper the shorter the time of thyristor opening. So, in the field of motor soft starter, most manufacturers are strong trigger to trigger the thyristor. Trigger pulse of the IG current amplitude is greater than or equal to 10IGT pulse rise time tr ≤ 1μs. In short. In order to ensure the reliability of the thyristor valve string, IG is much larger than the IGT,