CN2268340Y

CN2268340Y - Electricity-saving starting compensator for ac. asynchronous motor

Info

Publication number: CN2268340Y
Application number: CN 96235670
Authority: CN
Inventors: 容明芳
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-05-06
Filing date: 1996-05-06
Publication date: 1997-11-19
Anticipated expiration: 2006-05-06

Abstract

The utility model relates to an electricity saving starting compensator for alternating current asynchronous motors. The utility model comprises an air switch which is connected with three phase power supply, the make contact of an alternating current contactor, a starting control circuit and a capacitance compensator. The make contact of the alternating current contactor is connected between the capacitance compensator and the connecting end of the three phase power supply. A starting circuit is provided with a sequence control circuit which carries out the sequential control on the movement of the make contact. The utility model has the advantages that the starting current is reduced, the starting torque and the running power factor are improved, the side effect caused by compensation is avoided, and the problems of large starting current and much running energy consumption of the motor are better solved.

Description

AC asynchronous motor economize on electricity starting compensator

The utility model is a kind of economize on electricity starting compensator of AC asynchronous motor.

AC asynchronous motor (hereinafter to be referred as motor) is low because of simple structure, production cost, be convenient to advantages such as maintaining is widely adopted.But because motor belongs to inductive load, the phase place of voltage and electric current asynchronous (phase place of voltage is ahead of electric current), make it in alternating current circuit, exist intrinsic defective, promptly be power factor low, start the shortcoming more than reactive current big (be about rated current 5～7 times) and the operation power consumption.Big starting current externally can cause power transmission and transformation system voltage to reduce, and the equipment that has less voltage protector is stopped transport, and the lighting apparatus of high-intensity discharge is extinguished etc.; Internally can cause the startup of the motor of bringing onto load startup that difficulty (as driving the motor of air compressor) takes place.Because big starting current can cause the decline of supply voltage, and the terminal voltage of the detent torque of motor and motor square is directly proportional, so the decline of supply voltage also makes the torque of motor decrease, when the detent torque of motor during less than load resistance, system just can not normally start.Simultaneously, make the starting current of system and start-up time all above electrical network or overcurrent value and overcurrent time that system limited the start-up time of the corresponding again increase of the reduction of motor start-up torque system, trip protection then occurs, make system be difficult to start.In order to reduce the starting current of large and medium motor, adopt usually in the prior art to add autotransformer or starting drives such as reactor or resistor at the motor power end.Though these starting drives can reduce starting current, and eliminated substantially and started big electric current harmful effect that electrical network caused, but also make supply voltage on starter, produce pressure drop, the low situation of detent torque is worsened more, and said system starts the problem of difficulty and fails to improve and solve.Moreover the operation power consumption of motor greatly also is major issue anxious to be solved.Want head it off, must do from two aspects.Should improve the power factor of motor self on the one hand, at present, homemade power of electric motor factor has brought up to 0.82～0.86.Should improve the power factor of motor operation on the other hand.The operate power factor of motor and the power match of contained load are closely related, normal conditions, owing to will consider factors such as the fluctuation of line voltage and motor be supporting, the power output of actual institute employing motor often all is the power greater than contained load, that is to say the situation ubiquity of the low load with strong power that is commonly called as.If motor uses in this case, its power factor does not reach himself power factor, and the operate power factor of the motor through examining the overwhelming majority is between 0.7～0.8.When the operate power factor of motor is 0.8, its no work factor is 0.75, this means that the plant capacity to the motor power supply must be to increase 25% than motor power (output), compares with the motor that the reactive power full remuneration is fallen, meritorious electric weight will consume 56.25% more, and electricity wasting is serious.In order to address this problem, common way is that shunt capacitor carries out reactive power compensation on motor.Though this way is very effective, two drawbacks have been brought, first, capacitor increased the impulse current of motor in start-up course again, because when starting, need fill appearance, the starting current that can cause filling capacitance current and motor produces simultaneously, causes instantaneous large-current.The second, when motor cut out, capacitor can send electricity to give motor, and motor causes motor and building-out capacitor breakdown because of the coherence rotary electrification produces instant high-voltage easily.In sum, up to the present, the starting current of high power motor reaches operation power consumption problem greatly and does not still obtain the good comprehensive processing.

The purpose of this utility model provides and a kind ofly can make the startup of motor and the motor electricity saving starting compensator that the power consumption problem is well solved.

The utility model solution is as follows: it comprises the make contact (2) of the air switch (1) that is connected on the RST three phase mains end, A.C. contactor and is used to control the start-up control circuit (3) of this make contact (2) and is connected in parallel on capacitive compensator (4) on the RST three phase mains end, its key structure is: be connected to the make contact (5) of A.C. contactor between the parallel connected end of capacitive compensator (4) and RST three phase mains, be provided with the sequential control circuit that the action of make contact (2), (5) is carried out sequencing control in start-up control circuit (3).

In above-mentioned solution, the utility model adopts is the method for utilizing electric capacity leading current to be provided, reactive power is compensated for motor supply line, power factor during with raising startup and operation reaches the reduction starting current, improves detent torque and moves the purpose of economizing on electricity.Because the power of electric motor factor is to rise gradually along with the raising of rotating speed when starting, when motor did not reach rated speed, power factor was very low, only was 0.32.At this moment, need carry out relatively large compensation, promptly open all capacitive compensators reactive power.But, producing simultaneously for fear of the starting current that fills capacitance current and motor of capacitor, present technique utilizes sequential control circuit that separated the turn-on time of capacitor and motor, and then capacitor fills appearance earlier, starts behind the motor.Like this, when motor start-up, capacitor can compensate reactive power, improves the power factor when starting.According to

, under active power P and the changeless situation of line voltage U, electric current I and powerfactorcos are inversely proportional to.So, having improved power factor, starting current will decrease, thereby eliminates the influence of starting current to line voltage.Simultaneously, the compensation of capacitor also can improve the terminal voltage of motor, makes the corresponding raising of detent torque, and corresponding reducing started difficult problem and be resolved start-up time.When electrical motors when rated speed enters normal operating condition, be that power factor reaches at 0.7～0.8 o'clock, for the compensation rate that makes capacitor suitable, sequential control circuit can automatic disconnection part compensation condenser, power factor when making operation brings up to 0.9～0.95, reaches the purpose of operation economize on electricity.When motor cut out, sequential control circuit made capacitor break away from power supply and motor earlier, and then closes motor, and capacitor and motor disconnect mutually, have avoided the generation of instant high-voltage.

In sum, superiority of the present utility model is to have reduced starting current, has improved detent torque, shorten start-up time, improved the operate power factor, simultaneously, also avoided because the effect of paying that compensation produces, preferably resolved the problem of the big and operation power consumption of motor start-up electric current.

Describe its operation principle in detail according to embodiment below.

The functional-block diagram of Fig. 1 motor electricity saving starting compensator.

The circuit diagram of Fig. 2 small power motor economize on electricity starting compensator.

The circuit diagram of Fig. 3 middle low power motor electricity saving starting compensator.

The circuit diagram of Fig. 4 high and medium power motor electricity saving starting compensator.

Referring to Fig. 2, for small power motor, its starting current is less, and power supply facilities is not constituted harm, so present technique adopts the mode of quantitative compensation, promptly adopts single group capacitor compensation, starts with operation shared.Concrete structure is as follows: this starting compensator comprises air switch (1), A.C. contactor make contact (2) and the thermal relay (6) that is connected on the RST three phase mains end, wherein air switch prevents the motor short circuit electric current, contact (2) is controlled the operation of motor or is stopped, and thermal relay (6) prevents the overcurrent of motor operation; It also comprises the make contact (5-1) that is connected on the A.C. contactor between air switch (1) and the make contact (2), single group capacitive compensator (4-1) and the piezo-resistance (7) in parallel with building-out capacitor, wherein capacitive compensator (4-1) is used for the compensation of reactive power, the switching of contact (5-1) control compensation device (4-1), piezo-resistance (7) prevents the overvoltage of compensator (4-1); It also comprises a start-up control circuit, and this start-up control circuit is connected and composed by start button ON, stop button OFF, test button OF, the moving disconnecting point (8) of thermal relay, A.C. contactor KC1, KM1 and auxiliary relay JZ1, JZ2.This control circuit utilizes to be controlled motor the pickup time of JZ1, JZ2, KM1 and lags and start in capacitive compensator, and its time of lagging is 40～60ms.Because the appearance time of filling of capacitor is about 34ms, if the time interval of putting into operation of capacitor and motor is less than 34ms, can cause filling capacitance current and the motor start-up electric current produces simultaneously, cause instantaneous large-current, if this time interval is long, can cause overcompensation, supply line's voltage is raise, and idle refluence.So the accumulative total with JZ1, JZ2 and KM1 limits the time of lagging pickup time.The cumulative time of having utilized simultaneously JZ1, JZ2, KM1 to disconnect again can make motor lag and stop in capacitor 15～20ms, prevents that capacitor from send electricity to cause motor to produce instant high-voltage because of the inertia rotary electrification for the motor winding.The course of work of this starter is as follows: when needs start, lift ON, the control power supply enters the KC1 coil through break contact (8), button OFF, OF, ON and forms control loop, then KC1 energising, (9) adhesive of its break contact and self-insurance, its make contact (5-1) adhesive makes capacitor fill appearance, and its make contact (10) adhesive makes JZ1, JZ2, the KM1 adhesive of switching in proper order, motor is lagged start in capacitor 40～60ms.When needs stop, lifting OFF, KC1 coil elder generation dead electricity disconnects, and makes capacitive compensator break away from power supply and motor earlier, and then JZ1, JZ2, KM1 order dead electricity disconnect, and motor is lagged stop in capacitive compensator 15～20ms.Current transformer CT and ammeter A constitute Current Display among the figure, are used to show the motor start-up and the operating magnitude of current.Voltmeter V is used for display power supply voltage.

Referring to Fig. 3, for middle-size and small-size motor, can adopt two groups of compensation condensers (4-1), (4-2) to carry out compensation at regular time and quantity, (4-1) be the operation capacitive compensator, (4-2) for starting capacitive compensator, and in the start-up control circuit, be provided with a time relay JS1, lag and start by controlling motor the pickup time of JZ1, JS1, KM1 in capacitor.When starting, contact (5-1), (5-2) are closed simultaneously, capacitor (4-1), (4-2) are together dropped into start compensation; When normal operation, the time-delay break contact (11) of the time relay disconnects, and makes the KC2 dead electricity disconnect capacitor (4-2), only moves compensation by capacitor (4-1).Other the course of work is identical with Fig. 1.

Referring to Fig. 4, for large and medium motor, the way of output of motor itself is star-like startup triangular form operation, is connected into star-like output when promptly starting, and changes triangular form output during operation into.Therefore, corresponding again A.C. contactor KM2 and KM3 and the time relay J S2 of having set up on the basis of Fig. 3 is by the motor capacitor that lags is started.During startup, KM1, the KM2 adhesive of switching on makes the motor winding be connected into star-like output; When normal operation, time-delay make contact (12) adhesive of JS2, its time-delay break contact (13) disconnect, and then KM3 energising adhesive, KM2 dead electricity disconnect, and make the motor winding be connected into triangle output.For the ease of grasping the variation of electric motor system power factor in service, in Fig. 4, also be provided with the electric current and the power factor display circuit that are connected into by current transformer CT, ammeter A, power factor detector (15) and power factor meter (14).Other course of work is identical with Fig. 3.

Measure the curve checking by experiment, this starter can make the starting current of motor obviously reduce, and detent torque obviously increases, and obviously reduce start-up time.Simultaneously, the operate power factor can bring up to 0.9～0.95, economize on electricity 10～20%.

Claims

1, AC asynchronous motor economize on electricity starting compensator, comprise the air switch (1) that is connected on the RST three phase mains end, the make contact (2) of A.C. contactor and the capacitive compensator (4) that is used to control the start-up control circuit (3) of this make contact (2) and is connected in parallel on RST three phase mains end, it is characterized in that:

A, between the link of capacitive compensator (4) and RST three phase mains, be connected to the make contact (5) of A.C. contactor,

B, in start-up circuit (3), be provided with the sequential control circuit that the action of make contact (2), (5) is carried out sequencing control.

2, motor electricity saving starting compensator as claimed in claim 1, it is characterized in that: described capacitive compensator (4) can be provided with single group (4-1) or many groups (4-1) ... (4-n), and the make contact of A.C. contactor corresponding (5) with it can be single group (5-1) or many groups (5-1) ... (5-n).