U, V, W is on the stator 3 coil winding, 3 coil windings spool thread becomes 120°. Electrical machinery single-phase winding circular telegram time, the stable state torque may express is: T=f (i, theta). Among them, i the electric current which passes for the winding in; Theta is the electrical machinery rotor deviation reference point angle. Because the magnetic saturation effect may ignore, and the rotor structure is a circular, its 矩角 characteristic for strict sine,
Namely: T=k *I*sin (theta), k is the torque constant
If the ideal current supply take the permanent peak-to-peak value as I three-phase equilibrium electric current iU, iV, the iW supplies electrical machinery winding,
Namely:
IU=I*sin (wt)
IV=I*sin (wt+2*PI/3)
IW=I*sin (wt+4*PI/3)

Then the electrical machinery various interphase currents produce the stable state torque is:

TU=k*I*sin (wt) *sin (theta)
TV=k*I*sin (wt+2*PI/3) *sin (theta+2*PI/3)
TW=k*I*sin (wt+4*PI/3) *sin (theta+4*PI/3)

When stable state movement, theta=wt, then the three-phase winding produces the synthesis torque is:

T=TU+TV+TW=3/2*k*I*sin (PI/2-wt+theta) =3/2*k*I

Above analyzes indicated, regarding three-phase permanent magnetism synchronous machine, when three-phase winding input difference 120° sinusoidal current, because produces the circular rotary field in the interior, the electrical machinery output torque is the permanent value. Therefore, will exchange the servo-control principle to apply in the three-phase mixed style step of 进电 machine actuation system, the input 220V exchange, will become direct current after the rectification, again will pass through the pulse-duration modulation technology to become three groups steps and ladders types sine profile electric current, they separately have flowed three groups windings according to the fixed succession, its each steps and ladders correspondence electrical machinery will rotate step. Changes the electrical machinery rotational speed through the change driver output sinusoidal current frequency, but outputs the steps and ladders number had determined each step has transferred angle, when the angle goes past is small, then its steps and ladders number more, namely subdivides is bigger, theoretically said this angle may suppose enough small, therefore the thin score may be very big, but exchanges servo-control each step of angle and the feedback encoder precision has the very big relations, the general use is 2,500, therefore each step has transferred the angle is only 0.144, but this method controls step 进电 machine, Compared to if the is thin score is 10,000, then each step has transferred the angle is 0.036, therefore compared to common servo-control precision Gao Henduo. Certainly, when step of 进电 machine rotation, electrical machinery each 相绕�?inductance will form a reverse electromotive force, the frequency higher, the reverse electromotive force is bigger. Under its function, electrical machinery along with frequency (or speed) increases but the interphase current to reduce, thus causes the moment of force to drop, may cause when the electrical machinery low frequency and high frequency through 恒流 the way maintains the same interphase current thus enable the high frequency moment of force characteristic to have the improvement, this only can be when the low speed, therefore its overall performance (high low speed noise, high speed moment of force, high speed stable and so on) is very difficult to surpass the exchange servocontrol.

Chart 2 produces the difference 120° three-phase steps and ladders type sinusoidal current.

The three-phase mixed style step 进电 machine generally connects the three-phase winding the star type or the triangle, according to the electric circuit fundamental theorem, sum of the three-phase current is zero. Namely IU+IV+IW =0. Therefore usually only must produce two 相绕�?demand signals, the three-phase winding demand signal may by other two request. Similarly, only needs to the corresponding two 相绕�?actual electric currents to carry on the sampling, the three-phase winding actual electric current may obtain according to the type.

3 three-phase mixed style step of 进电 machine drivers system constitution

Driver overall plan like chart 3 shows, mainly includes the monolithic integrated circuit electric circuit, the electric current tracing SPWM electric circuit and the power actuation electric circuit composition.

Chart 3 driver overall diagram

3.1 DSP module design
In here, we chose TI Corporation's DSP to take the CPU chip, DSP (Digital Signal Processor) also was one kind of monolithic integrated circuit in fact, it similarly was the central processing element, controls the control unit and the auxiliary equipment integrates together on the chip. But it also has own bright characteristic - because has used the multi- groups main line technology realization parallel movement machine the mechanism, thus greatly enhanced the operating speed, has the stronger operation ability and a better timeliness. This article selects DSP (TMS320LF2407A) is a section electrical machinery control special-purpose chip, 144 pins, have the rich IO resources, includes four general timers, special-purpose has two groups (to be possible to produce six group PWM signal) to the control three-phase electrical machinery PWM generator, moreover also has the special-purpose receive exterior pulse and the direction I/O mouth, thus simplified the circuit design and the procedure development.
The DSP input signal including step enters pulse signal CP, the heading command, the off-line signal, has flowed the protection signal. These kind of signals connect DSP through the high speed light pair on the pin, moreover also has subdivides the step and the electric current selection signal. When off-line signal for is effective time, the driver outputs the electrical machinery the electric current to shut off, the electrical machinery rotor is at the free state (off-line condition). The feedback electric current brings through DSP 10 modulus switches (AD) the sampling, the feedback electric current after the certain algorithm, brings the PWM mouth output control electrical machinery by DSP.
3.2 electric currents tracing return route
This transmission mode simulates the voltage the peak-to-peak value to represent the sampling electric current or the voltage size, it mainly uses for sampling a, the b two interphase currents and the generatrix voltage examination, realizes the electrical machinery electric current control as well as has pressed, owes presses, has flowed the protection. The driver through the sampling resistance examination step of 进电 machine winding actual electric current, compares the process after the hypothesis electric current to stagnate the link comparator regulator, the regulator output signal by the 20KHz frequency triangle wave carrier output, forms the pulse-duration modulation signal (PWM), controls the high efficiency semiconductor device through the power actuation connection electric circuit to lead passes with shuts off, causes the step of 进电 machine winding actual electric current track to assign the reference signal, according to sine rule change which assigns.
3.3 powers actuations electric circuit
The driver main return route uses hands over - the straight - alternating current 压型 inversion form, by the rectification filter circuit, the three-phase inversion as well as step 进电 machine and so on is composed. Rectification filter circuit constitution direct current 电压�? completes 220V, the 50Hz alternating current supply to the direct-current power supply transformation. The inversion realization from the direct current to the frequency conversion live pressure alternating current transformation, provides the request for the three-phase mixed style step of 进电 machine stator winding the alternating current. The inversion six G30N60B3DMOS tube which produces by the young attendants to the immortals company composes, constitution three-phase inversion bridge. The driver uses two resistances examinations step of 进电 machine interphase current the spurt value.
The power actuates the electric circuit the core is the power module (the MOS tube). The MOS tube and between the electric current tracing PWM output must through the special-purpose high speed light pair connection. The flow value and the electrical machinery peak value line electric current selects the appropriate MOS tube according to the MOS tube, namely the electrical machinery line electric current peak value is smaller than the MOS tube maximum current value. In this design the electrical machinery biggest interphase current is 8.1A, this electric current is the interphase current 有效�? the peak value interphase current is 8.1* sqrt (2) = 11.312A. In addition, electrical machinery winding when triangular connection, the line electric current is interphase current 3 times, therefore the line electric current peak value is 19.6A. By the G30N60B3DPDF documents knowledge, its greatest flow value is 30A, therefore may guarantee the normal use, the normal work request suitable radiation design guarantee interior ties warm forever is smaller than 150 degree Celsius, therefore wants the sur- radiator and forces the forced-air cooling, guarantees the MOS tube normal work.
3.4 and mouth communication:
In order to avoid when the controlled process power cut or other special reasons falls the electricity causes the losses, the use charged RAM memory electrical machinery position, after guaranteed the electricity the work piece may continue to complete the processing. And mouth RAM compared to traditional use E2ROM speed transmission quickly more reliable, may the more effective record electrical machinery running status, but takes CPU the I/O mouth to be more, here CPU has the enough resources to be allowed to use.
3.5 controls software flow
Master routine flow chart

Severs the partial flow charts

In order to reduce the power loss and the protection electrical machinery, has established the automatic half class function, it by stagnates the link comparator automatically to carry on the adjustment.

4 conclusions
The practice proved this article says actuation method its compatibility very strong, basically may adapt all three-phase mixed styles step 进电 machine. Specially to three-phase winding star connection, low frequency when moves steadily, does not have the vibration, effectively has suppressed the vibration, the noise. Moreover, the driver internal design many kinds of protection circuit, makes the entire driver the reliability greatly to enhance.
Reference
[ 1> Li Yongdong Alternating current machine numerical control system, mechanical industry publishing house, 2002.4;
[ 2> Lin Weijie, Li Xinggen, Pan Anke A three-phase mixed style step of 进电 machine sine wave subdivides the actuation the research;
[ 3> Wei Kexin, Wang Yunliang, Chen Zhimin MATLAB language and automatic control system, mechanical industry publishing house;
[ 4> the Liu peace, Wang Wei are handsome, Jiang Yu, Deng strength TMS320LF240X DSP the C language development application, the Beijing astronautics university publishing house;