The hottest thyristor soft starter will gradually

Thyristor soft starter will gradually replace the traditional self coupling compensator

Abstract: as an energy-saving controller, soft starter has been widely promoted in China since the early 1990s. After years of practice, it has been proved that thyristor soft starter is superior to the traditional self coupling compensator. With the promotion of localization, the traditional self coupling compensator will be phased out

key words: thyristor soft starter; Energy saving controller; Self coupling compensator; Introduction in intelligent soft starter

1

in 1977, Frank nole engineer of NASA obtained a patent for economizer, which was initially called "power factor controller". Since then, many companies and individuals have developed more than a dozen kinds of economizers. In 1982, franknole made two further improvements, one was to monitor the voltage at both ends of the thyristor instead of the sampling resistance, and the other was to adopt the feedback control technology, so that the motor voltage was further reduced under no-load, and the power saving rate was greatly improved, which was officially named "powersaver". Is the friction force too large? China has also developed energy-saving appliances, but the actual use effect is poor, and it has not been widely used. After 1983, Shanghai successively introduced a series of energy-saving products. On the basis of digesting and absorbing the introduced energy-saving products, Shanghai, Xi'an and other places developed new energy-saving products, whose performance reached and exceeded that of the introduced similar products, creating conditions for further promotion of energy-saving products. Since the 1990s, soft starter has been the preferred product for motor energy conservation in the domestic market

2 as a soft starter for energy-saving applications

the economizer realizes voltage reduction through bidirectional thyristor or anti parallel thyristor phase control. Its main circuit principle is shown in Figure 1

see Table 1 for the measured data of thyristor soft starter (refer to the measured data of 30kW motor). It can be seen from table 1 that

1) the economizer has a good power saving effect

benefit for some specific loads. Therefore, it should be popularized and used in the corresponding range, and it should not be used regardless of the object

2) for constant loads (whether full load or load rate of 30% ~ 40%), continuous and long-term operation, it is not suitable to use the economizer, but should choose high-efficiency motors

3) for variable load conditions, if the minimum load rate is ≥ 30%, it is of little significance to use thyristor soft starter

3 technical and economic comparison between soft starter and self coupling compensator

traditional self coupling compensator has been playing a major role in the field of motor starting devices since it was applied in the early 1950s. Since the 1980s, foreign solid-state starting devices have been gradually popularized and used in China's industrial field, which has had a great impact on the traditional compensator. Table 2 compares the technology and economy of the two devices, and gives the correct application range for readers' reference

4 technical characteristics and application scope of soft starter

1) machinery with short-term repeated work

long-term no-load (light load 40%) operation and short-term heavy load. For example: cranes, belt conveyors, metal material calenders, lathes, punches, planers, shears, etc

2) frequently started working machinery

some machines are often in the start and stop state. If light load starting is allowed, soft start technology can be used. The following is a list of the characteristics of some soft start actuators that strive to continue to improve their market share. a) Linear soft start

this starting method is the most commonly used. First, the motor rises to the initial torque value, which can be adjusted between 5% and 90% of the rated torque. Then, the motor voltage rises gradually during the rise time of the acceleration ramp, and the rise time of the acceleration ramp can be adjusted between 2 ~ 30s. As shown in Figure 2. b) Soft start with selectable jump start

this starting mode provides jump start and boost. It can provide current pulse of 500% full load current, and the adjustable time range is 0.4 ~ 2S. Add an additional torque when the motor needs to be boosted to start due to load. As shown in Figure 3

NVIDIA: both heat aging resistance and excellent processing performance C) pump control

this function reduces the surge in the pump system by smoothly accelerating and decelerating the motor during the start and stop of the centrifugal pump. The microcomputer analyzes the motor variables and sends out control commands to control the motor in a way that reduces the possibility of surge in the system. The starting time can be adjusted between 2 ~ 30s, and the stopping time can be adjusted between 2 ~ 120s. As shown in Figure 4

d) intelligent motor braking

the control system can realize the occasions where the motor needs to stop faster than free parking, that is, fast braking. It is a microcomputer based braking system, which provides three-phase braking current to the standard squirrel cage induction motor. Braking is completed without additional contactors or power supply equipment, and automatic zero speed parking is implemented without timers, sensors or tachometers. The strength of braking current can be adjusted between 150% and 400% of full load current. The compensator cannot complete this function. As shown in Figure 5

e) low speed braking

this function is mainly used for the forward low-speed positioning and braking of the motor

Table 2 Comparison of three step-down starting performance step-down starting methods autotransformer star delta conversion thyristor soft starter

starting voltage K · UE (0.3 ~ 1.0) ue

starting current K · ied how should we choose? Next, our technicians will introduce the classification of spring fatigue testing machines and how to choose suitable equipment? (0.3 ~ 1.0) ied

starting torque K2 · MGD (0.3 ~ 1.0) MGD

characteristics and advantages and disadvantages of various starting methods. When starting under light load, the starting impulse current is small and the starting torque is large, but frequent starting is not allowed. The secondary impulse starting current is small when switching, and the starting torque is small. It is only suitable for small capacity below 20kW. The starting current can be arbitrarily specified from (20 ~ 400)% to limit the starting torque and protect mechanical safety, Light load can save energy

the price of the self coupling compensator and its copper and silicon steel consumption and the corresponding soft starter price control motor power/kw self coupling starter ABB soft starter price/yuan

price/yuan consumption copper/kg consumption silicon steel/kg

15 ~ 223900 00

20～374050.. 00

455500.. 00

556400.. 00

756700.. 00

908700.. 00

.. 00

.. 00

.. 00

180～.. 00

220～.. 00

280～.. 00

occasion of automatic control parking. The slow modulation speed is 7% of the rated speed (low) or 15% of the rated speed (high). The low-speed acceleration current (within 2S) can be adjusted between 50% and 400%. The braking current can be adjusted between 150% and 400%. Jump start is not allowed. Low