The asynchronous motor and does not need the characteristic by its fine performance which maintains, obtains the widespread application in all the various trades and occupations. However because time its starting must produce the bigger surge current (generally is Ie 5-8 time), simultaneously because the starting stress is bigger, causes the load equipment loss of life. The national department concerned starts to the electrical machinery early has explicitly stipulated, namely the electrical machinery will start when the electrical network voltage will not be able to surpass 15%. Solution has two: (1) Increases the power distribution capacity; (2) Uses the limit electrical machinery initial firing current the trigger, if merely increases for the starting motor matches the electric capacity, said from the economical angle, obviously cannot take. Therefore, the people often need to provide the limit electrical machinery initial firing current the trigger, in the past the people used the Y/ �? transformation, fell the pressure from the lotus root, the magnetism controlled falls presses and so on the way realizes. These methods although may certainly play limit flow the role, but fundamentally has not solved the problem. Along with the electric power electronic technology fast development, the intelligence 软起�?obtains the widespread application. The intelligence 软起�?is one kind of collection 软起�? softly stops, 轻载 the energy conservation and the multi-purpose protection to a body novel electrical machinery control device, also is called Soft Starter. It not only realizes in entire starting process does not have the impact but the smooth starting motor, moreover may adjust in the starting process according to the electric motor load characteristic the parameter, like limits the flow value, the starting time and so on. In addition, it also has many kinds of to the electrical machinery protection function, this fundamentally solved the tradition to fall presses the trigger many malpractices.

2 软起�?performance comparisons

West of the peaceful cubic science and technology limited company produces the CTS series alternating current machine 软起�?for regularly explains the principle of work and the movement characteristic: Three phase ac asynchronous motor starting moment Ma directly with adds the voltage quadratically related, in other words, so long as reduces electrical machinery binding clamp on the voltage to be able to affect these values. 软起�?the principle of work is with is controlled by the series connection to the power source between the electrical machinery three opposite parallel crystals thyratron to carry on moves the pressure, the passable adjustment crystal thyratron has led passes the angle to cause the electrical machinery 端子 the voltage from the value which establishes in advance to rise to the rated voltage. Chart 2 showed the CTS series 软起�?control system diagram which the cubic science and technology company produced.

3 startings ways have (1) the voltage double pitch starting: Like chart 3 shows, in the starting process, the electrical machinery output moment of force increases along with the voltage, when starting provides initial starting voltage Us, Us may move according to the load, adjusts Us is bigger than the load static friction moment of force, enables the load to start to rotate immediately. By now the output voltage started from Us according to the certain slope rise (slope to be possible to move), the electrical machinery unceasingly accelerated. When the output voltage achieved when reaches fast voltage Ur, the electrical machinery also basically achieves the rated speed. 软起�?the automatic detection reaches the fast voltage in the starting process, when the electrical machinery achieved when rated speed, enables the output voltage to achieve the rated voltage. (2) limits flows the starting: Is in the electrical machinery starting process limits its initial firing current not to surpass some as soon as supposes the definite value (Im) 软起�?the way. Its output voltage starts from zero rapidly to grow, until the output current achieved establishes in advance electric current limiting value Im, then the maintenance output current I this kind of starting way merit is the initial firing current is small, also may according to the need adjustment. Affects slightly to the electrical network, its shortcoming is in the starting critical moment knew the starting pressure drop, cannot fully use the pressure drop space. (3) 突跳 starting: In the starting initial stage, lets the crystal thyratron all lead after the extremely short time passes recedes, again presses the original hypothesis the value linearity rise, enters 恒流 the starting, this starting technique is suitable to the heavy load and must overcome the bigger 静摩�?starting situation. Like chart 4 shows 软起�?the movement characteristic: (1) can cause the electrical machinery starting voltage by the constant slope steady rise, the initial firing current to be small, to the electrical network non- surge current, reduces the load the machinery impact. (2) the starting voltage rise slope might move, had guaranteed starting process smoothness, the starting voltage might rest on the different load (Ue is rated voltage) in the scope continuously may move in 30% ~ 70%Ue. (3) may act according to the different load hypothesis starting time. (4) the starter also has the silicon-controlled rectifier to short-circuit the protection, lacks protects, the hot protection, has owed presses the protection.

4 软起�?applications situations

Now the market has the many kinds of models 软起�?to be possible for the user choice, a different product function not only is also same, the choice is the suggestion follows the following principle. In principle, asynchronous machine every does not need to modulate velocity each kind of application situation all may use, is suitable pumps a kind of load or the air blower class load to each kind, needs 软起�?with softly to stop (solution 水锤 effectiveness) regarding 变负�?the operating mode, the electric motor is in 轻载 the movement for a long time, only has short now and then instantaneous is in the full load movement situation, the application 软起�?(does not bring bypass contact device) to have 轻载 the energy conservation effect.

5 软起�?MCC control cabinet

MCC (Motor Control Center) controls the cabinet, namely motor control center. 软起�?controls the cabinet to be composed by the below several parts: (1) the input end circuit breaker, (2) 软起�? (3) 软起�?the bypass contact device, (4) two sides control circuit (completes manual starting, remote control starts, 软起�?and function and so on direct-on starting choice and movement), 有电�? electric current demonstration and breakdown, movement, active status equisignal demonstration. 软起�?the MCC control cabinet further performs to combine or with the PLC logic control, may realize the many kinds of compound functions. Uses in the building fire prevention system with to spray pumps, the life pumps and so on the system. May realize the fire extinguishing pump fixed time automatic detection, fixed time automatic shut-off; Adds on the corresponding control logic, then may cancel pumps and each system revolves whether normally, the implementation usually examines time, fixed time low speed low hydraulic pressure movement; When fire fighting, then implements the full speed full load movement. Certain Taiwan Telegraphic Transmission motive control logic combination, may compose the life to pump the system or other special-purpose systems, gradually starts each Taiwan Telegraphic Transmission machine according to the required quantity, also may gradually reduce the electrical machinery, the realization best efficiency movement. Also may realize the multi- Taiwan Telegraphic Transmission machine automaticswitching movement, causes various electrical machinery all to be in the same level movement life.

6 concluding remark

The CTS series 软起�?widely applies to all the various trades and occupations and so on metallurgy, steel and iron, oil field, along with the our country economy fast development, the high-rise construction, business trade building, the recreation center modernized construction are more and more many. Its air conditioning and the fire request is more and more high, but the tradition falls presses the trigger as a result of the inherent weakness, has been unable to satisfy the modernized construction the need, therefore the choice intelligence electric motor trigger, is the inevitable development direction.