Motor flexible braking control and zero-speed detecting system based on solid-state soft starter
Technical field
The present invention relates to the dragging of motor, control technology, promptly a kind of motor zero-speed based on soft starter detects and the braking control technology.
Background technology
As many industrial machineries such as lathes, all need be equipped with motor as the power that drives, and need motor to have the function of quick parking.So far, have only the part solid-state soft starter to possess braking function, and it is mainly based on " plug braking ".
So-called " plug braking " when being meant the ac three-phase asynchronous motor braking, changes the phase sequence of any two-phase power supply in its input power supply, and the direction of rotation in motor internal magnetic field is changed, that is, the motor internal FR is rotated.At this moment, produce an opposing torque between opposing magnetic field and rotor, and hinder rotor and load forward rotation, dragging motor retarding braking.
Solid-state soft starter, control antiparallel high-power thyristor (controllable silicon) with single-chip microcomputer as the control core, it can realize the control of voltage magnitude, phase sequence, frequency etc. to its output easily by various algorithms, so solid-state soft starter can be realized plug braking easily.During plug braking, soft starter at first cuts off motor power, and its output survey phase sequence is determined according to the phase sequence of the three-phase alternating-current supply that is checked through in the time-delay back, promptly, make outlet side wherein two phase sequences exchange, and the three-phase alternating-current supply that will change phase sequence puts on the motor.Its principle is: Single-chip Controlling thyristor (controllable silicon) angle of flow increases gradually, its outlet side voltage is increased gradually, and promptly braking moment increases gradually, reach rated voltage to the soft starter output voltage after, it is maximum that braking moment reaches, thereby realized the braking of motor easily.
The soft starter plug braking, simple than the traditional mechanical brake structure, good braking effect, and failure rate is low, however this mode braking procedure mechanical shock is big, and braking procedure control is complicated, is prone to the phenomenon of motor braking process upset.
Summary of the invention:
The objective of the invention is to, overcome the deficiency of prior art, provide a kind of current collection machine zero-speed to detect and dynamic braking in the motor soft starter of one, the braking procedure that makes motor is steadily, fast.
The present invention is based on following design and finishes:
The present invention is platform with the soft starter, is keeping having increased the dynamic braking device on its conventional func basis of invariable, and hardware circuit is taken into account soft starter routine work state and soft starter dynamic braking operating state.This dynamic braking device also can be called the DC injection braking device, it comes down to a direct current power supply is put on the two-phase stator winding of AC three-phase asynchronous motor, make and produce a fixed magnetic field between this two-phase stator winding, this fixed magnetic field of rotor rotation cutting, produce a moment of resistance and stop rotor rotation, thereby realize motor braking.Braking procedure require to possess braking impact little, accurately judge motor speed, braking time is controlled automatically.Adopt the mode of two-phase half-wave controlled rectification in the braking procedure, close the third phase thyristor.The DC power supply of soft starter output slowly increases during braking, to reduce increasing the too fast mechanical shock that causes owing to voltage increases the too fast braking moment that causes.By the detection that third phase stator winding before the motor stall is produced induced electromotive force, accurately judge whether stall of motor.Half second finishes braking procedure after the motor braking stall, thereby realizes the automatic adjusting of braking time.
The present invention is achieved in that
In order to realize the dynamic braking function, the present invention makes improvement from hardware circuit and two aspects of software program.
The hardware circuit of this system is made up of major loop 4 and control circuit.Major loop 4 has many thyristors, contactor KM1 (main normally opened contact KL1, auxiliary normally-closed contact NC1), heavy-duty diode; Constitute a phase valve group after per two thyristor inverse parallels; SCR1 and triggering signal a are electrically connected in the auxiliary normally-closed contact NC1 of contactor KM1 and the valve group, and contactor KM1 master normally opened contact KL1 and is valve group output and heavy-duty diode D1 electrical connection mutually; The heavy-duty diode D1 other end and another valve group output electrical connection mutually; Control circuit is made up of single chip machine controlling circuit 1, man-machine interface 2 and peripheral testing circuit 3, and single chip machine controlling circuit 1 is electrically connected with man-machine interface 2, peripheral testing circuit 3 respectively; Peripheral testing circuit 3 is electrically connected with major loop 4.Major loop 4 has 3 groups of antiparallel thyristors (controllable silicon).Peripheral testing circuit 3 has been set up motor zero-speed testing circuit on each basic testing circuit basis of invariable of the former soft start of reservation, in order under on-position, to detect the operating condition of motor, judge whether stall of motor, and cut off the soft starter braking according to this stop point and export, 3 20K Ω sampling resistors of this motor zero-speed testing circuit are formed the Y type and are connected, and input is electrically connected with the output of major loop 4 respectively; Rectifier DB107 ac input end one end is electrically connected with major loop 4 output sampling resistors that T3 is connected, and the other end is connected common point and is electrically connected with sampling resistor Y type; Optocoupler 6N139 input is surveyed and is electrically connected with rectifier DB107 direct current outlet side, and optocoupler 6N139 outlet side collector electrode C is electrically connected with Schmidt's reverser 74HC14, increases pull-up resistor R at this place simultaneously, to distinguish high-low level.Be electrically connected to optocoupler 6N139 outlet side emitter E and control level; Schmidt's reverser 74HC14 outlet side is electrically connected with single chip machine controlling circuit 1.
The present invention is provided with software program, and control motor braking, zero-speed detect:
One, motor braking control, carry out following program:
A) braking is prepared: cut off bypass contactor, cut off soft starter output, time-delay drops into braking contactor and unloads puts diode.Set the braking procedure initial voltage, for pre-braking is prepared;
B) pre-braking: the highest brake voltage of this stage is for setting 10% of brake voltage, and the braking time is 500mS in advance, and brake voltage begins slow increase by 0V, braking output voltage V=dv*ti/T (dv: set 10% of brake voltage; Ti: current braking time; T: brake time 500mS in advance); If pre-braking time no show and brake voltage has reached when setting brake voltage 10%, braking output voltage are kept 10% to the pre-braking time of setting brake voltage and are arrived; If pre-braking voltage do not reach set brake voltage 10% and pre-braking time is up when reaching, finish pre-braking process;
C) the brake voltage slope increases: the output brake voltage began to increase when this graduated application voltage was finished by pre-braking, the brake voltage that the highest brake voltage is set for the user, the brake voltage slope increase time is set 30% of braking time for the user, braking output voltage V=dv*ti/T (dv: set brake voltage; Ti: current braking time; T: set braking time 30%); During the braking time no show, if the braking output voltage is set brake voltage less than the user, then braking output voltage continue to increase and to set brake voltage until the braking output voltage with the user and equate; If the braking output voltage is set brake voltage with the user and is equated that then braking output voltage no longer increases; When braking time arrives, no matter brake output voltage and whether set brake voltage and equate, all will finish braking, cut off brake voltage and export with the user;
D) braking total head output: before the braking time no show, all will keep the output user and set brake voltage.
Two, the motor zero-speed detects the following program of carrying out: behind pre-braking end and braking beginning 700mS, single-chip microcomputer begins scan module zero-speed testing circuit, and after detecting the pulse that pulse duration reaches 1.5mS, assert the motor stall, no matter be in that process of braking this moment, all will after half second, finish braking, cut off output.
Operation principle of the present invention is as follows:
Under the soft starter routine work state: the major loop of soft starter is made of the antiparallel thyristor of three-phase (controllable silicon), microprocessor is by carrying out phase shifting control to this three-phase inverse parallel SCR, thereby the voltage and current that control is added on the motor changes motor torque smoothly, realizes soft or soft stopping of motor.When soft of motor after reach full speed running; current of electric drops to the current value of normal full speed running by limited current state, and soft-starter control bypass contactor closure makes electric current flow into motor through bypass contactor; soft start is carried out whole process protection as monitoring equipment to motor.
Under the soft starter dynamic braking operating state: dynamic braking is a DC injection braking, and the present invention adopts the mode of half-wave controlled rectification when dynamic braking, and AC power is adjusted is DC power supply, for motor braking provides braking power.The thyristor (controllable silicon) that microprocessor is only controlled in the major loop carries out phase shifting control, just can realize the control to output dc voltage, thereby realizes the control to braking moment.
Thyristor flows through motor windings when turn-offing electric current changes, and just produces the variation that induced electromotive force suppresses electric current as the motor windings two ends of inductive load.The direction of this induced electromotive force is opposite with the direction of braking power, can influence the braking effect of motor.In order to reduce the influence of inverse electromotive force, in circuit, increase suitable leadage circuit this inverse electromotive force is discharged braking effect.
In order to increase work efficiency, must monitor the operating condition of motor.During dynamic braking, motor two-phase stator winding applies DC power supply, makes and produces a fixed magnetic field between this two phase winding.Rotor and loading under the action of inertia is rotated further, rotor coil cutting fixed magnetic field, and on rotor coil, produce the electric current of an alternation.An inductance transformer is formed in the motor stator winding coil of third phase access failure power supply and the equivalence of stator winding coil, so also respond to the induced electromotive force that has produced an alternation on the motor third phase winding.Detect this induced electromotive force by testing circuit, just can effectively monitor motor speed.
By apply a Constant Direct Current power supply to motor windings, the induced electromotive force that discovery third phase winding is sensed when braking test is bigger in braking initial stage amplitude, and frequency is higher, what brake induced electromotive force change in mid-term is not clearly, and can sense one group of AC signal that amplitude is big and frequency is little, the cycle is long in the moment of motor stall.Induced electromotive force can be judged the motor stall more accurately herein, and induced electromotive force herein can be convenient is detected.Therefore after the induced electromotive force rectification that motor can not produced on the third phase stator winding of input DC power, the filtering, input detecting circuit.After testing circuit isolates this induced electromotive force, change, handle, give the detection input of single-chip microcomputer as motor speed with the signal of handling.
For the support circuit operation, and realize dynamic braking function and motor zero-speed measuring ability, must on the basis of former soft starter program, increase the braking control program, and in the braking control program, inlay motor zero-speed trace routine.
In order to realize two-phase half-wave controlled rectification, must be by detecting this two-phase power supply phase sequence, and be benchmark with the zero crossing of a phase power supply wherein, with another mutually the power supply zero crossing compare, thereby sentence the phase order relation of this two-phase power supply.After determining the phase order relation, can by with the reach of the zero crossing of reference power supply or after move the line voltage zero-cross point that 30 degree electrical degrees are made this two-phase power supply.Just can control the conduction position and the conducting electrical degree of thyristor as benchmark after calculating this zero crossing, realize the half-wave controlled rectification.
During braking, in order to reduce the electric and mechanical shock of motor and load, braking procedure comprises pre-braking, and the brake voltage slope increases, three parts of full voltage braking.During pre-the braking, brake voltage slowly increases to sets 10% of brake voltage, so that rotor is slowly slowed down, avoids rotor and load rotating shaft collision, reduces mechanical shock.After braking time to be stipulated finished, soft starter output brake voltage slowly increased in the mode on slope, thereby makes braking procedure more smooth-going.Behind the brake voltage that the brake voltage of exporting equals to set, soft starter will be kept this voltage, make the motor fast braking.
Because motor rotor speed is subjected to load effect in pre-braking process, this moment, spinner velocity changed instability, can produce frequency height and the big fluctuation of amplitude on the motor third phase winding, surveyed in order flase drop not occur, detected so will not carry out the motor zero-speed in this process.Increase and the full voltage output stage on the brake voltage slope, single-chip microcomputer will be assert the motor stall with continuous scanning detecting circuit after detecting the pulse duration appropriate signal, and cut off output behind half second, finish braking.
The present invention has increased flexible braking and motor zero-speed measuring ability for solid-state soft starter preferably keeping on the every conventional func basis of invariable of solid-state soft starter.
Description of drawings
Fig. 1. the schematic block diagram of unitary construction;
Fig. 2. motor zero-speed testing circuit schematic diagram;
Fig. 3. main program flow chart;
Fig. 4. the control subprogram flow process;
Fig. 5. braking procedure schematic block diagram.
Embodiment
Below in conjunction with embodiment of accompanying drawing narration, the present invention will be further described.
Fig. 1 shows the circuit structure of present embodiment integral body.Present embodiment is mainly reached and is formed based on the major loop 4 of thyristor (controllable silicon SCR) by single chip machine controlling circuit 1, man-machine interface 2, peripheral testing circuit 3.
Single chip machine controlling circuit 1 is the maincenter of whole soft starter in order to realize the fuzzy control and the correlation computations of soft starter.2 of man-machine interfaces realize the control of people to equipment in order to finish human-computer dialogue.Peripheral testing circuit 3 is in order to detecting power phase, the electric current in the circuit, and the state of thyristor (controllable silicon), the temperature of equipment etc. realize the on-line monitoring to equipment, for every defencive function provides foundation.
Major loop 4 ties up to improve on the basis of former soft starter circuit and forms, L1, L2, L3 are the power input terminal of soft starter, T1, T2, T3 are the lead-out terminal of soft starter, major loop 4 is made up of 3 groups of antiparallel thyristors (controllable silicon), the triggering signal a of single-chip microcomputer output is in order to trigger SCR1, SCR4, triggering signal b is in order to trigger SCR2, SCR5, and triggering signal c is in order to trigger SCR3, SCR6.Contacts of contactor NC1, KL1 and heavy-duty diode D1 have been increased in order to the braking major loop.During braking, use the auxiliary normally-closed contact MC1 of contactor KM1 to open, cut off the triggering signal a of SCR1, make SCR1 in braking procedure, be in off state, be i.e. do not work during SCR1 braking.Single-chip microcomputer stops the triggering signal c of output-scr 3, SCR6, makes SCR3, SCR6 be in off state.Single-chip microcomputer output triggering signal a makes SCR4 be in fully conducting state in whole braking procedure, and single-chip microcomputer is a benchmark with the power line voltage zero crossing, constantly calculates triggering signal b, control SCR2, SCR5 conduction position.Soft starter output T1 is the positive pole of DC power supply during braking, and output T2 then is the negative pole of DC power supply, and output T3 is the input of motor zero-speed testing circuit.With contactor master normally opened contact KL1 closure, make heavy-duty diode D1 place in circuit during braking,, fast this inverse electromotive force is released with so that the inverse electromotive force that motor windings produces forms the loop.
Fig. 2 shows motor zero-speed testing circuit.During braking in order in the circuit that exists a large amount of alternating current components and DC component to mix, to detect the zero-speed signal of motor, use the resistance of 3 20K Ω 3W to form Y type network, and three ends of this Y type network lead-out terminal T1, T2, the T3 respectively at soft starter connected, thereby for the output of soft starter is set up reliable interchange neutral point, the induced electromotive force when making the motor stall can be detected easily.Use electric capacity that high-frequency signal is subdued in the circuit, and use high speed photo coupling 6N139 that high low-voltage is isolated, use Schmidt's reverser 74HC14 that detected signal is carried out oppositely and filtering high frequency clutter.Give single-chip microcomputer with detected signal at last, whether stop operating in order to judge motor.
Fig. 3 shows main program flow.The operating state of soft starter comprises: stop programming, fault; Starting process, stopped process; Three kinds of total heads.The operating state of main program cycle detection soft starter selects to carry out the corresponding program section according to the work at present state of soft starter.
10~17 is the original program of soft starter among Fig. 3, and this subprogram is carried out corresponding program according to the operating state of soft starter and finished every function as the main body of program.The operating state of soft starter comprises: 12. total heads and stop, parameter editor, fault show state and 13. starting or stopped processes.
14. in starting or the stopped process, whether the three phase mains that at first need judge soft starter phase shortage, if phase shortage is then carried out 15. troubleshootings, and shows ' Err1 '; If phase shortage is not then carried out 16. and called the triggering subprogram, calculate trigger position and send triggering signal.
17. every interval 10mS calls a block (keyboard and I/O mouth sampling subprogram segment, A/D conversion routine section, control subprogram section).
Fig. 4 shows the control subprogram flow process.The porch of control program adopts the mode of tabling look-up to select the current control program that needs execution, and control program comprises: start the time-delay control program; Leakage current detect control program before the operation; The kick control program; The voltage ramp control program; The current ramp control program; Operation Current limited Control program; The total head control program; The crawl control program; The soft control program that stops; The brake control program.The control program that wherein brakes is a key of the present invention, and other control program is original primary control program (PCP) of soft starter.
The brake control subprogram comprises: 20. braking control initialization and 27. braking execution subroutines.
21. braking is prepared: cut off bypass earlier, close triggering behind the time-delay 100mS, and then control brake contactor adhesive behind the time-delay 100mS, connect the braking major loop, it is ready to brake required hardware circuit.
22. braking time is set: extracting parameter C007 is as braking total time, and whole braking procedure must not surpass this time.
23. with brake voltage 10% as pre-braking voltage dv, braking time T in advance is 500mS, output brake voltage V=dv*ti/T, ti is the time that braking procedure consumes.
It is 0 that 24. the initial brake voltage of braking procedure is set, and calculates the trigger angle position by look-up table, i.e. the triggering signal and the phase voltage zero crossing time interval, and this trigger angle moved 25 degree backward, the time interval that is about to calculate increases 1.4mS.
25. finish braking initialization setting, return main program, the output triggering signal.Begin to carry out braking after treating to enter once more behind the 20mS braking control subprogram.
Fig. 5 is a braking procedure.
28. judging pre-braking finishes? pre-braking process voltage slowly increases with braking moment, and motor slows down gently, makes contacting that motor shaft and load can be mild, and has alleviated mechanical shock, avoids owing to the excessive and damage equipment of mechanical shock.
29. before pre-braking is finished, and do not detect motor zero-speed signal in the braking beginning back 700mS, thereby avoid because braking initial stage braking procedure instability causes the influence of motor zero-speed jitter to system's operate as normal.Begin to detect motor zero-speed signal behind the braking beginning 700mS, keep above 1.5mS when the zero-speed signal and assert that then motor stops operating.
30. the braking countdown finishes, promptly braking time has reached total braking time of setting, and then whether stall all will be cut off brake voltage output to motor, avoids motor stator winding owing to apply DC power supply for a long time but motor temperature raises, and burns motor.
The braking procedure of motor comprises: 31.500mS brakes in advance, and 34. brake voltage slopes increase and three steps of 37. setting brake voltage outputs.
Slowly increase 32. brake the process output voltage in advance, utilize formula V=dv*ti/T to calculate an output voltage every 20mS.(the formula explanation sees 23)
Set 10% of brake voltage 33. the output of braking process in advance maximum voltage is no more than, the braking time is no more than 500mS in advance.
After 35. pre-braking is finished, voltage is with 30% time as the direct voltage slope of braking time (C007), brake voltage slowly increases, avoided the quick increase (braking moment and brake voltage are exponential relationship) of braking moment, alleviate the mechanical shock of equipment, prolonged the useful life of equipment.Brake voltage dv for setting in the parameters C 008 is 30% T of the maximum braking time of setting in the parameters C 007, known current braking time ti, then current braking output voltage V=dv*ti/T.
36. must not surpassing, maximum output brake voltage sets brake voltage.
37. current output voltage with set brake voltage and equate after, braking output voltage slope increases finishes, output voltage will no longer change, and keep the brake voltage of output setting.
Obtain trigger angle 38. table look-up, and will move 35 degree after the trigger angle.
39. show the braking procedure countdown, and return main program.
40. after satisfying the end of braking requirement, time-delay 1.5S closes and triggers and braking contactor, finishes braking.