SU655037A1 - Contact-free dc drive - Google Patents

Description

The invention relates to pulse-width modulation systems and it can be used to increase the accuracy and simplify a drive with contactless DC motors with positional 110 dependent modulation of phase voltages (BDPT PM). A non-contact direct current drive is known in which the stabilization of the speed is accomplished by the tachometric negative feedback of the motor. As speed sensors of these drives, as a rule, irreversible synchronous tachogenerators with permanent magnets 1 are used. Pulsations of the output rectified voltage of such tachometers reach 14%, which reduces the accuracy of the drive using synchronous speed sensors especially at low rotational speeds of the engine when it is difficult filtering the specified pulsations. The presence of a tachogenerator complicates the drive. The actuator 2 is known in which there is no tachogenerator, and the stabilization of the speed is achieved by forming a more rigid mechanical characteristic in a contactless DC motor by adjusting the duration of connecting the motor phase to the mains. The adjustment is carried out parametrically by subtracting from the interval determined by the rotor position sensor a predetermined time interval. The disadvantage of the device is that the regulation is carried out at the frequency of rotation. This reduces the accuracy of the adjustment. The prototype of the invention is a device 3J, which contains a non-contact direct current drive with a pulse-width magnetic modulation position sensor. It stabilizes the speed using an additional converter, which reduces the accuracy of the speed stabilization. The aim of the invention is to improve the accuracy of speed stabilization. This goal is achieved by combining the functions of the pulse-like magnetically-modulated rotor position sensors (DPR), which are part of the BDT PM, with tacho generator sensors. For this, a series of pulse delay circuits, a modulo two adder, a pulse expander, and a barring logic circuit are connected to the circuit of each phase of the PDU PM, and the output of the PDR driver is connected to the input of the delay circuit, to the first input of the modulo adder, to the second the input of which is connected to the output of the delay circuit, and to the input of the inhibit logic, and the output of the modulo two adder is connected to the input of the pulse expander, the output of which is connected to the inhibit input of the inhibit logic, output cat swarm connected to the input of the power wrench motor phase.

Thus, the signal about the rotational speeds of the engine is obtained in a pulsed form, as in the prototype, however, in the proposed device, the closure of the negative speed coupling is performed in each phase and without additional conversion (in the pulsed form), which provides an increase in the accuracy of the drive .

FIG. 1 shows a functional diagram of the drive; in fig. 2 shows diagrams explaining the principle of drive operation.

The drive consists of three pulse-width DPR 1, 2, 3, connected by its outputs to the input of three drivers 4, 5,

6. The shaper outputs are connected to the first inputs of the adding logic modulo two 7, 8, 9 directly, and to the second inputs through the pulse delay circuits for the carrier frequency period 10, 11, 12. The outputs of the adding logic modulo two 7, 8 , 9 through pulse remover 13, 14, 15 are connected to prohibit inputs of the inhibit logic 16, 17, 18, to the inputs of which are connected the outputs of the formers 4, 5, 6. The outputs of the inhibit logic 16, 17, 18 are connected to the inputs of the power switches 19 , 20, 21, commuting motor windings.

Since the circuit consists of three identical channels, according to the number of phases of the engine, consider the operation of one channel.

FIG. TI curve 2 depicts the dependence of the relative pulse durations of the rotor position sensor 1 for the first phase.

Pulses with DPR 1, the relative duration of which is determined by the position of the shaft BDIT PM, are fed through the shaper 4 to the first input of the addition logic module modulo two 7 directly, and to the second input through the delay delay circuit, for the period of the carrier frequency 10. In addition, the pulses from the output of the driver 4 are fed to the input of the inhibit logic 16. In the absence of a signal at the inhibitory input of the circuit 16, the pulses from the output of the driver 4 through the logic circuit 16 control the operation of the power switch 19, which commutes one of the phases engine When the motor shaft rotates with an angular velocity i at the output of the logic circuit of addition modulo two

7, pulses appear, the relative duration of which tu varies according to the law

with/

where 1t is the amplitude of change in relative duration;

and - the angle of rotation of the rotor BDPT PM. The magnitude T m is determined by the speed of rotation of the shaft BDPT PM. The pulses from the output of the logic circuit modulo two 7 are fed to the expander 13, which performs the functions of amplifying the pulse width signal U of speed. FIG. 2

The curves And, QS, QZ depict the dependences of the relative pulse duration from the output of the expander 13 at various shaft rotation speeds BDPT PM and, moreover. So the output

expander 13 circuits receive a pulsed signal L / i with a relative capacitance of t,

U, KpSma

// (l

t

where K. p - the coefficient of pulsing, / C - the transmission coefficient of the device

speed measurements, and - angular velocity of the shaft

BDPT PM.

The pulses of the L / i signal are fed to the inhibit input of logic circuit 16, which performs the functions of subtracting the pulse signals Up and Ui. The relative duration of the signal at the input of the prohibition scheme 16 can be written as

Vr

and 1

TI i: j, sina Oh, / CATpSsina.

40 Then

() sma.

It can be seen that the pulses arriving through the power switch 19 on the winding of the BDPT PM winding have a relative duration of Tu, which is sinusoidally dependent on the angle of rotation of the rotor. From the expression for the amplitude of change, it can be seen that in the phase of the engine

negative speed feedback is performed. Thus, the engine in each phase is covered by a negative tachometric feedback. The feedback factor can be varied by changing, for example, the expander factor 13 / Cp of the device.

Thus, in the proposed drive, by combining the functions of the pulse-pickup angle sensors with the tachogenerator sensors in each phase, negative speed feedback is maintained while maintaining the sinusoidal dependence of the relative duration of the power supply pulses on the angle of rotation.

rotor providing non-pulsing