SU1721738A1 - Gated electric drive directly energized by dc network - Google Patents

Abstract

The invention relates to electrical engineering and can be used in actuators for various purposes with digital control. The aim of the invention is to simplify, increase efficiency by increasing the average torque value and reducing its ripple. To this end, in a valve-driven actuator with direct AC power, the rotor position sensor 6 is made with three outputs for performing position-dependent switching, a pulse-width modulator is common to all channels 15-17 of the control unit with its code input connected to the bus control signal and the output of the generator 18 pulses. The outputs of sensor 6 are connected respectively to three inputs of the reverse unit made on the EXCLUSIVE OR element 7. The first input of the reverse unit is connected to the control sign bus, and the third and fourth inputs of each channel of the control unit are connected to the power inputs of one of the bridge switches 2-4 . The elimination of a number of nodes from an electric drive circuit allowed the phase voltage modulations of the synchronous machine 1 to be rejected as a function of the angle of rotation of its rotor. 5 ill., 1 tab. W Ј

Description

The invention relates to electrical engineering and can be used in actuators for various purposes with digital control.

The aim of the invention is to simplify the drive, increase the efficiency and uniformity of rotation by increasing the average value of the torque and reducing its pulsations.

FIG. Figure 1 shows a functional electrical circuit of a valve motor drive with direct AC power; in fig. 2 is a functional diagram of a bridge switch for one phase of a synchronous machine; in fig. 3 is a variant of connecting bridge switches to an AC mains with galvanic isolation from the primary network; in fig. 4 - connecting bridge switches without a matching transformer; in fig. 5 shows graphs of the relative torque of a synchronous machine versus the angle of rotation of the shaft over the entire range of changes in the phase of the network.

The valve motor contains a synchronous machine 1 with a three-phase

VI

 SA) 00

a corona winding, galvanically developed phases of which are connected respectively to the outputs of bridge switches 2-4, the power inputs of each of which are equipped with clips for connection to one of the phases a, a1; b, bi; with, with AC 5 network. On the shaft of the synchronous machine 1, a rotor position sensor 6 is installed, made with three outputs for performing position-dependent commutation.

The valve actuator also contains a reverse unit with four inputs and three outputs and a logic control unit.

The reverse unit is composed of three or two input logic elements EXCLUSIVE OR 7, the combined first inputs of which form the first input of the reverse unit intended for connecting the control signal to the bus slgnAg. The second inputs of logic elements 7 form the second, third and fourth inputs of the reverse unit, respectively, connected respectively to the outputs of the rotor position sensor 6b. The outputs of logic elements 7 form the corresponding outputs of the block reverse.

The logical control unit is made of three channels, each channel of which is composed of a comparator 8, three logical elements EXCLUSIVE OR 9-11, and two inverters 12 and 13. The combined first inputs of the first 9 and second 10 control logic elements form the first input of the logical control unit connected to one of the outputs of the reverse unit. The second input of the logic element 9 forms the second input of the aforementioned channel connected to the output of a pulse-width modulator (PWM) 14. The second inputs of the second 10 and third 11 logic elements. EXCLUSIVE OR connected to the output of the comparator 8, and their outputs to the inputs of inverters 12 and 13. Comparator 8 is made of two-input, forming the third and fourth inputs of this channel, respectively, connected to the power inputs of one of the bridge switches 2-4. The first input of the logic element 11 is connected to the output of the logic element 9. The outputs of the logic elements 10, 11 and inverters 12, 13 form the outputs of this channel of the control unit, connected respectively to the control inputs of one of the bridge switches.

PWM 14 is made common to all channels 15-17 of the control unit. Its code input serves to connect to the dd bus.

control input, and the clock input is connected to the output of the pulse generator 18.

The switch for one phase of the winding of the core is composed of four keys 19-22 (see Fig. 2) connected in a bridge circuit, the terminals a, and the alternating currents of which form the power inputs of the switch, and the terminals of its second diagonal form the outputs of the switch.

Each bridge switch 2-4 can be connected to the network X, Y, Z by means of a matching transformer 23 (see Fig. 3) or without it (see Fig. 4). In the latter case, the network has a neutral wire N.

The valve actuator operates as follows.

In PWM 14 with the frequency fw, the control code Dd is recorded from the bus.

In this case, the frequency Tm is chosen in accordance with the ratio

)

where fr is the generator frequency.

The control pulse duration t for a specific dd is

., -. #;

Thus, the fill factor of the PWM pulses of all phases of the synchronous machine 1 is equal to m DD

u .. and I w 9 -h

(3)

2n-1 where Tm - the period of the pulse PWM.

The control unit of the i-th phase on the basis of the signals e, h, s generates the signals A, B, C, D of the control keys 19-22 of the bridge switch in accordance with the table

Logical variables (signals e. H. S) are defined as follows. The output signal e of the comparator of the main channel of the control unit is equal to a logical zero with a negative polarity of the mains voltage relative to the neutral of the AC network 5 and a logical one otherwise. The value of the PWM output signal h 1 determines the connection of the i-th phase of the core winding to the mains phase, h 0 corresponds to the dynamic braking of the synchronous machine 1 by short-circuiting the 1st phase. The value of s 1 determines the direction of current flow in the 1st phase from the beginning to the end and vice versa and can be found as

rt

s sign Ag + sign sin (Od | l1), i 0, 2

where Od is the rotation angle of the rotor of the synchronous machine,

which sets the reverse of the valve electric drive when the value of sign Ag is changed by simultaneously inverting the signals s of all phases, which leads to a change in the direction of current in all phases and a change in the sign of the torque. Signal-

2

Sign sin sin (Gg + i) is removed from the outputs of the rotor position sensor 6, which, taking into account the polarity of the mains voltage, determines the direction of current of the phases of the core winding from the current phase of the network.

Minimized logical equations derived from the table. Have the form

A e® (s © h);

C e s s;

D S.

The unit values of the key control signals 19-22 determine their closed state and vice versa.

The phases of the core winding of a synchronous machine to the supply voltage are connected as follows. Let at the initial moment the values of the signals h. s, e are as follows: h 0, s 0. e 0. At the outputs of logic elements 9-11, they have logical zeros, at the outputs of inverters 12, 13 - logical units. In this case, the keys 19 and 21 are open, and the keys 20 and 22 are closed, which corresponds to the dynamic braking mode. When changing the value of h (h 1) at the outputs of logic elements 9 and 11, the signals of logical units correspond to the closure of switches 19 and 22 and the opening of switches 20 and 21 and the flow of current in the winding from end to beginning. When changing the sign e of the supply voltage (e 1), the signal of the logical unit 10 appears at the output of the logic element 10, and the logical zero at the output of the logic element 11, the keys 20 and 21 close, the keys 19 and 22 open, and the direction of the current in the phase remains unchanged. The change in the direction of the current in the phase occurs only when the signal s changes. When the signal s goes to a logical unit (for the values of h 1, e 1), the outputs of the logic elements 9, 10 appear as a logical zero, the logic element 11 is a logical unit and the keys 20 and 21 open and the keys are closed

19 and 22, which corresponds to the flow of current in the winding from the beginning to the end. Bridge switches 2-4 must be implemented on two-way conductor keys (simistors, field effect transistors, pairs of bipolar transistors).

The positive effect of the invention is achieved by not modulating the phase voltages of the synchronous machine 1 as a function of the angle Od of the rotation of the shaft according to harmonic laws.

sln (Og + | l: |), 1 (G2.

This makes it possible to significantly simplify the valve motor drive, to exclude a controlled frequency divider, two PWM, and permanent memory. An analysis of the polarity of the mains voltage either relative to the neutral of the three-phase network (see Fig. 4), or relative to the other terminals of the secondary windings of the matching three-phase transformer (see Fig. 3, when the terminals ab are not connected) allows the use of a three-phase transformer with the output of the secondary points of the secondary windings, and for high-voltage synchronous machines - and from the use of a matching three-phase transformer (see FIG. 4), thereby significantly improving the drive weight and dimensions and increasing its efficiency. In addition, the use of a simple and reliable sensor for positional switching dependency instead of an expensive digital angle sensor significantly reduces the cost of the drive and increases its reliability. This allows the average torque to be raised and its pulsations reduced.

Indeed, if we consider the starting operation modes of the drive for all possible angular positions Od of the rotor of the synchronous machine Od - 0 - 2l :, changing for each particular Od network phase from 0 to 2l:, then a zone of torque values will be obtained for arbitrary Od and time points. The analysis shows that in the known device (see Fig. 5) this zone is limited by the curves Е - F, and in the proposed device by the curves ЕУ-F, i.e. with a fixed Od moment, M pulsates with a network frequency from the value of MI to MI, i 1, 2. Calculation of the pulsation DM | according to the formula

AMG

M | Max M

1 MINUTE

100%

gives for the first AM-i device 66%, for the proposed DM2 device 50%, which indicates a decrease in torque ripple by. sixteen%. In addition, from

the graph (see Fig. 5) shows that in the proposed drive, the torque reaches the maximum possible value for Moms at a given supply voltage (100% of Mmax border F), a M2cpfi75% of Mmax, whereas in the first device MI max & Q% of Mmax (curve F), while Mmax and, therefore, an increase in the average moment is 15% without an increase in the supply voltage.

It should be emphasized that in the dynamic mode, the pulsations of the voltages of the core windings are smoothed by the electromagnetic inertia of the phases, and the electromechanical inertia of the motor smoothes the pulsations of its torque.

Thus, by eliminating a certain number of logic and power elements and using a simpler rotor position sensor, it was possible to significantly reduce the ripple torque of the electric drive and raise its average value, which plays a crucial role for a number of applications of the described electric drive (robotics, machine tools CNC etc.) ..

Claims (1)

Invention Formula An AC-powered valve actuator containing a synchronous machine with a three-phase core winding, galvanically developed phases of which are connected respectively to the outputs of three bridge switches, the power output of each of which is equipped with clips for connecting to one of the phases of the AC power supply a rotor mounted on the shaft of a synchronous machine, a reverse unit with four inputs and three outputs, the first input of which serves to connect a control air sign to the tire ystvi, three-channel logic control unit, each channel trehvhodovy which is composed of interconnected a comparator, three logical elements EXCLUSIVE OR, and two inverters, the outputs of which and the outputs of the second and third logical elements connected to The inputs of the inverters form the four outputs of this channel connected to the control inputs of the corresponding bridge switch, the first input of each channel of the control unit formed by the combined first inputs of the first and second logic elements EXCLUSIVE OR of this channel is connected to one of the outputs of the reverse unit, the second input is mentioned channel, formed by the second input of its first logical element EXCLUSIVE OR, is connected to the output of a pulse-width modulator, and the third input of each channel of the unit board the input of its comparator is connected to one of the power inputs of the corresponding bridge switch, a pulse generator, characterized in that, in order to simplify, increase efficiency and uniformity of rotation by increasing the average torque value and reducing its ripple, the rotor position sensor has two additional outputs for the implementation of position-dependent switching, the sensor outputs are connected respectively to the second, third and fourth inputs of the reverse unit, the pulse-width modulator is made common im for all three channel block control, the code input of the pulse-width modulator is used to connect to the control bus, and the clock input is connected to the output of the pulse generator, the comparator of each channel of the control unit is provided with a second input forming the fourth input of this channel connected to another power input of the corresponding bridge switch Yy fa Z.JA 1 I-G- & F No Fiz.g FiaZ Fzg.5 Fy Schz Sffi 2Я