CN101075796A - Flexible starter for electric motor - Google Patents

Abstract

The invention comprises: an electronic controller, a main circuit control unit, and a keyboard. The three-phase power is connected to the motor through said main circuit control unit; the electronic controller is connected to the main circuit control unit; the keyboard is connected to the electronic controller. Said electronic controller is made by making reverse parallel connection for three pairs of thyristors; each phase is connected to two thyristors reversely parallel-connected and after connecting to the stator winding in series, is connected to the AC power.

Description

Motor soft start device

Technical field

The present invention relates to a kind of starting and control device of motor, more particularly it is a kind of motor soft start device.It is specially adapted to the starting and the control of powerful asynchronous motor.

Background technology

At present, the motor of the China and the external overwhelming majority all adopts asynchronous motor, as: blower fan, water pump, electric machines for roller, belt motor etc.And often during these more powerful electric motor startings, electric current is excessive all will to produce adverse influence for power supply network and motor itself.Excessive cranking current pulse will cause the fluctuation of line voltage, and influence hangs over the normal operation of other electric machinery and apparatus on the same electrical network.For motor itself, excessive starting current will make motor itself be subjected to the impact of excessive electromagnetic force, if often starting, also might make overheated the burning out of winding of motor, and starting torque is little, to be prolonged the starting time of dragging system, thereby have influence on the productivity ratio of manufacturing machine.

Summary of the invention

This utility unit provides that a kind of circuit is simple, reliability is high, energy consumption is low, the motor soft start device little to electromechanical shock.

The Electrical Motor principle is told us:

$I_2^{\&prime;}=\frac{U_1}{\sqrt{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="A20071005191300091.png"\; state="\{\{state\}\}">r</figure-callout>}}_1^2+x_1^2}}---\left(1\right)$

I in the formula ₂Rotor current when being motor starting;

U ₁Be applied voltage;

r ₁Resistance for motor;

x ₁Reactance for motor;

As seen from formula (1), rotor current during motor starting is directly proportional with applied voltage, under the big inadequately situation of capacity that motor got access to grid, when not allowing to adopt across-the-line starting, can adopt the way that reduces applied voltage to reduce starting current, soft starter device utilizes exactly

The method is come starting motor.

The operation principle of soft starter device: this device utilizes controllable silicon electronic switch characteristic, by changing trigger impulse, the size of trigger angle changes the conducting degree of thyristor, thereby changes the three-phase voltage that is added to stator winding, reaches the purpose of speed governing and control motor.

The objective of the invention is to reach: motor soft start device by following measure, it comprises electronic controller 1, main circuit control device 2, keyboard 3, three phase mains is connected with motor by main circuit control device 2, electronic controller 1 is connected with main circuit control device 2, keyboard 3 is connected on the electronic controller 1, it is characterized in that described electronic controller 1 is with three pairs of controllable silicon reverse parallel connections, the controllable silicon and the motor stator windings in series of two reverse parallel connections that whenever are connected are received on the AC power.

In technique scheme, the phase sequence that six controllable silicon gate poles on the described electronic controller 1 trigger is: controllable silicon electronic switch VT1, VT3, the triggering phase place of VT5 lags behind 120 ° successively, controllable silicon electronic switch VT4, VT6, the triggering degree of the VT2 VT1 that lags behind respectively again, VT3,180 ° of VT5, triggering phase place is 60 ° from VT1 to VT6 space lag successively, passes through circuits for triggering, form the trigger impulse of six different periods, the size of trigger angle changes the conducting degree of thyristor.

In technique scheme, the control main flow of described main circuit control device 2 is: during startup

Program initialization 01---→ holding state 02---→---→ adhesive bypass contactor 04---→ excision soft starting device 05---→ the return holding state 02 that starts soft starting device 03;

When stopping

Program initialization 01---→ holding state 02---→ excision bypass contactor 06---→ with soft starting device motor is stopped 07---→ excision soft starting device 08---→ return holding state 02.

Soft start motor soft start device of the present invention has following advantage:

(1), starting current rises to set point with certain slope, and electrical network is not had impact.

(2), introduce Current Negative Three-Point Capacitance in the starting process, after starting current rises to set point, promptly keep steady state value, make electric motor starting steady.

(3), be not subjected to the influence of voltage ripple of power network,, when line voltage fluctuates up and down,, regulate the terminal voltage of motor, still can keep the starting current constant, guarantee the motor normal starting by the angle of flow of increase and decrease thyristor because soft start is set point with the electric current.

(4), at the requirement of different loads to motor, can stepless adjustment starting current set point, change the electric motor starting time, realize the control of optimum start time.

Description of drawings

Fig. 1 is the circuit structure block diagram of motor soft start device of the present invention.

Fig. 2 is the main circuit diagram of motor soft start device of the present invention.

Fig. 3 is the flow chart of motor soft start device of the present invention.

Fig. 4 is the pressure regulation machinery performance plot of motor soft start device of the present invention.

Fig. 5 is voltage, electric current, the rotation speed relation figure of motor soft start device of the present invention.

Fig. 6 is dissimilar parking curve chart.

Fig. 7 is for slowing down into slope map.

Embodiment

Below in conjunction with the performance of accompanying drawing detailed description motor soft start device of the present invention, but they do not constitute limitation of the invention, only give an example, simultaneously by illustrating that advantage of the present invention will become clear more and understanding easily.

Consult Fig. 1 as can be known: motor soft start device of the present invention, it comprises electronic controller 1 (electronic controller model: AP8100, for Britain FAIRFORD ELECTRONICS LTD company produces), main circuit control device 2, keyboard 3, three phase mains is connected with motor by main circuit control device 2, electronic controller 1 is connected with main circuit control device 2, keyboard 3 is connected electronic controller 1, it is characterized in that described electronic controller 1 is with three pairs of controllable pair reverse parallel connections, the controllable silicon and the motor stator windings in series of two reverse parallel connections that whenever are connected are received on the AC power.

Consult Fig. 2 as can be known: the phase sequence that six controllable silicon gate poles on the electronic controller 1 of the present invention trigger is: controllable silicon electronic switch VT1, VT3, the triggering phase place of VT5 lags behind 120 ° successively, controllable silicon electronic switch VT4, VT6, the triggering degree of the VT2 VT1 that lags behind respectively again, VT3,180 ° of VT5, triggering phase place is 60 ° from VT1 to VT6 space lag successively, by circuits for triggering, forms the trigger impulse of six different periods, the size of trigger angle changes the conducting degree of thyristor, thereby changes the effective value of output voltage.

When soft device starting motor, regulate phase shifting angle α by circuits for triggering, the output voltage of bidirectional thyristor increases gradually, motor quickens gradually, and when motor speed rose, circuits for triggering made phase shifting angle d=0, this moment, controllable silicon was as diode, make output voltage impose the total head conducting, motor moves with rated current, and this moment, soft device starting motor process finished.

Consult Fig. 3 as can be known: starting process: soft starter powers on, self check, enter holding state after the program initialization, starting order under the operating personnel, soft starter starting, motor begin starting, treat the motor stabilizing operation after, system automatically switches to corresponding bypass operation, and excising soft starter automatically, soft starter is got back to holding state, proceed-to-send.

Docking process: after the cutoff command, system switches to the soft starter operation from the bypass operation automatically under the operator, and motor begins to stop by design curve, and after motor stopped, soft starter stopped automatically, and got back to holding state, stopped to finish the following Fig. 3 of flow chart;

This device is made up of main circuit control device, phase voltage current detecting, electronic controller and keyboard.As figure Fig. 1, shown in Figure 2, the main circuit control device is made up of six inverse parallel controllable silicons, and its conveyance capacity is strong, and switch motion is fast; Voltage current transformer is formed phase voltage current detecting part, and the phase voltage electric current is detected in real time, has protected the main circuit control device not burnt; Electronic controller is made of master control borad, trigger board, and it is the control centre of soft starter device, and the work order of whole device is all sent by it.Keyboard is installed in the device, is connected on the Electronic Control plug-in unit, and it can be provided with and revise parameter, can show the running status of soft starter device simultaneously again.

Consult Fig. 4 as can be known: machine operation is on the mechanical property of rated voltage; the output voltage of controllable silicon soft starter device reduces; guaranteed the unlikely maximum permissible value that surpasses of main circuit current; realize smooth starting; thereby overcurrent tripping when avoiding starting; played the overcurrent protection effect, and the mechanical property during low speed is harder, thereby bigger starting torque can be provided.

Consult Fig. 5 as can be known: the major control mode of AC asynchronous motor soft start has two big classes: the one, by the restriction starting current, control by torque, its purpose all is under the prerequisite that satisfies the load torque demand, enough accelerating torques are provided, the motor that realization has load smoothly accelerates to rated value, realizes soft start by current limliting.Can Fig. 4 explanation.The 2nd, by the control (being that voltage progressively increases by certain slope) of motor terminal voltage, the starting current of motor is limited (little more than direct-on-line starting), and rotating speed of motor increases gently simultaneously, accomplishes electric machine soft starting.Can find out also that from Ben Tu load has static friction torque, for this reason at the voltage given initial stage, need an impact voltage (about 25%～75% is adjustable), we are referred to as starting voltage; This rear motor increases according to a slope, and we are referred to as ramp voltage.By applying starting voltage (less than rated voltage) and ramp voltage, realized the restriction starting current, consequently voltage is the great-jump-forward variation, and the speed as shown in Figure 4 and the relation curve of torque operate on another characteristic curve motor.

Consult Fig. 6 as can be known: for the parking of electric-driving installation as shown in Figure 6, some kinds of methods are arranged, i.e. DC (direct current) braking, free inertia stops, soft stop.Soft stop is to satisfy those demands to the mild plant equipment of docking process requirement.As pump, be to prevent that speed from stopping, cause the rate of flow of fluid sudden change, cause the pressure cataclysm, the bottled drink production line suddenly stops easily causing fragmentation etc. for another example.

Consult Fig. 7 as can be known: stopping has two classes in control: speed prompt drop slope (see figure 7), the braking (DC injection braking) under the torque control.The former is called soft stop.The latter also disposes in the soft start product that has and is selected voluntarily by the user.

Claims (3)

1, motor soft start device, it comprises electronic controller (1), main circuit control device (2), keyboard (3), three phase mains is connected with motor by main circuit control device (2), electronic controller (1) is connected with main circuit control device (2), keyboard (3) is connected on the electronic controller (1), it is characterized in that described electronic controller (1) is with three pairs of controllable silicon reverse parallel connections, the controllable silicon and the motor stator windings in series of two reverse parallel connections that whenever are connected are received on the AC power.

2, motor soft start device according to claim 1, it is characterized in that the phase sequence that six controllable silicon gate poles on the described electronic controller (1) trigger is: controllable silicon electronic switch (VT1, VT3, VT5) triggering phase place lags behind 120 ° successively, controllable silicon electronic switch (VT4, VT6, VT2) the triggering degree (VT1 that lags behind respectively again, VT3, VT5) 180 °, trigger phase place from (VT1) to (VT6) successively space lag be 60 °, pass through circuits for triggering, form the trigger impulse of six different periods, the size of trigger angle changes the conducting degree of thyristor.

3, motor soft start device according to claim 1 is characterized in that the control main flow of described main circuit control device (2) is:

During startup

Program initialization (01) → holding state (02) → startup soft starting device (03) → adhesive bypass contactor (04) → excision soft starting device (05) → return holding state (02);

When stopping

Program initialization (01) → holding state (02) → excision bypass contactor (06) → motor is stopped (07) → excision soft starting device (08) → return holding state (02) with soft starting device.

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