SU765958A1 - Device for determining dc electric motor rotational speed - Google Patents

Description

(54) DEVICE FOR DETERMINING ROTATION FREQUENCY

one

The invention relates to electric drives, in particular to a direct current electric drive with motors, which are controlled both by changing the voltage on the bark and by changing the magnetic flux and can be used in electric drives of hoisting-and-carrying machines, excavators, mine hoisting machines, rolling mills mills

A device for determining the rotational speed of a direct current motor is known, which contains magnetic flux sensors and motor EMF and a multiplier-dividing device, n (the connection to the outputs of these sensors is ill- The disadvantage of this device is the poor accuracy of determining the frequency of rotation of motion 1 & with a large range of change in the magnetic flux of the engine, especially when driven by an electric drive with a change in the sign of the magnetic flux.

Closest to the invention to the technical essence and the achieved result, is a device for determining the frequency of rotation; no dc motor, dc co-motor

holding sensors EMF and magnetic flux of the engine, two summing amplifier connected to the input

5 of the first summing amplifier, a DC voltage source, two diodes, a nonlinear converter, two key elements and a sign inverter, the output of the motor magnetic flux sensor through the nonlinear converter connected to the input of the first summing amplifier, the output of which is connected to the input of the second summing Wux, Lyapha through the first key element and serially connected inverter of the sign and the second key element, and the output of the motor EMF sensor is connected to the input of the second summing amplifier and

20 through the first and second diodes to the control inputs of the first and second key elements, respectively, t2-l

.Lack of this device

25 is the low accuracy of determining the rotational speed of an engine with a large range of magiHTHoro electric motor flux, especially with a simultaneous and independent change in the magnetic flux and voltage on the core and in the case of electric drive control with a change in the sign of the magnetic flux.

The purpose of the invention is to improve the accuracy of determining the frequency of rotation of a DC motor.

This is achieved in that a device for determining the rotational speed of a DC motor, containing sensors for EMF and magnetic flux of the motor, two summing amplifiers connected to the input of the first summing amplifier, a constant voltage source and two diodes, a multiplying unit, two additional diodes and the node forming the sign of the rotation frequency, and the EMF and magnetic flux sensors of the engine and the second summing amplifier are made with inverting and non-inverting outputs, and non-inverting and inverting Guiding the outputs of the magnetic flux sensor of the engine through the first and second diodes connected to the input of the first summing amplifier, the output of which through the multiplication unit, the second input of which is connected to the non-inverting output of the second summing amplifier, is connected to the first input of the second summing amplifier, the second input of which through the third and fourth the diodes are connected to a non-inverted and inverted outputs of the motor EMF sensor, and the outputs of the second summing amplifier are connected to the inputs of the hour mark forming unit rotational rods, to the inputs of the task of the sign of which the outputs of the sensors of the magnetic flux of the motor EMF are connected. The motor speed sign forming unit is made in the form of a multiplication unit connected to the character input inputs of this node, two additional resistors, four coupled-to-opposite diodes and an additional operational amplifier, in the chains of each of the two inputs of which are connected in series an additional resistor and diode The common points between which through the third and fourth diodes are connected to the output of the multiplying unit of the specified node. Improving the accuracy of determining the frequency of rotation of the engine is also ensured by the fact that the node forming the sign of the rotation frequency is made in the form of four logical elements AND-NOT, two additional resistors, six diodes and connected between the output of the specified node and its inputs connected to the non-inverting and inverting outputs of the second summer an amplifier, an additional operational amplifier, the circuits of each of the two inputs of which include a series-connected additional resistor and a diode, a common point The third and fourth diodes connected to the first diode and connected to the first diode are connected to the first and second logic elements AND-NOT, the common point between the additional resistor and the diode in the second input circuit of the operational amplifier is connected through the fifth and sixth diodes connected to the second diode diodes with the outputs of the third and fourth logical elements AND-NOT, the input of the node forming the sign of the rotation frequency connected to the non-inverting output of the EMF sensor of the engine connected to the inputs of the first and third lo I-NOT, the input of this node, connected to the inverting output of the motor EMF sensor, is connected to the inputs of the second and fourth NAND logic elements, the input of the specified node, connected to the non-inverting output of the engine magnetic flux sensor, is connected to the inputs of the second and third logical elements AND-NOT, and the input of this node, connected to the inverting output of the magnetic flux sensor of the engine, is connected to the inputs of the first and fourth logical elements AND-NOT.

FIG. 1 shows a diagram of an apparatus for determining the frequency of rotation of a direct current motor; in fig. 2 and 3 are diagrams of a node for forming the sign of the rotation frequency.

A device for determining the frequency of rotation of a DC motor comprises sensors EMF 1 and magnetic flux 2 motors, two summing amplifiers 3 and 4 connected to the input of the first summing amplifier 3 constant voltage source 5, diodes 6, 7, 8 and 9, block multiply 10, node II of the formation of the sign of the rotation frequency. The EMF 1 and magnetic flux sensors 2 of the engine and the second summation amplifier 4 are made with inverting and non-inverting, gyro outputs, while the non-inverting and inverting outputs of the magnetic flux sensor 2 of the engine through the first .6 and second 7 diodes are connected to the input of the first cymbal amplifier 3, the output of which is through the multiplication unit 10, the second input of which is connected to the non-inverting output of the second summing amplifier 4, is connected to the first input of the second summing amplifier 4, the second input of which is through the third 8 and quarters The 9 diodes are connected to the non-inverting and inverting outputs of the EMF sensor 1 of the engine, and the output of the second summing amplifier 4 through the node II for vm of the rotation speed sign, to the inputs of which the character is connected to the outputs of the EMF sensors 1 and the magnetic flux 2 of the engine, is the output of the device for determining engine speed.

The node 11 forming the sign of the motor rotational speed (see Fig. 2) is made in the form of a sign of this node connected to the input, connected to the outputs of the EMF sensors 1 and magnetic flux 2 of the engine of the multiplication unit 12, two additional resistors 13 and 14, four diodes 15 , 16, 17 and 18 and connected between the output of the node 11 and its inputs are connected to the non-inverting and inverting outputs of the second summing amplifier 4, the additional operational amplifier 19, the connected sequences are included in the circuits of each of the two inputs flax additional resistor and diode (13 and 15, 14 and 16), common points between which through the third 17 and fourth 18 diodes are connected to the output of the multiplication unit 12 of the TI node

The node II of forming the sign of the rotation frequency (see Figs. 2, 3) is performed in the form of four AND –NE logic gates 20, 21, 22 and 23, two additional resistors 24 and 25, six diodes 26-31 and connected between the output of the indicated node 11 and its inputs connected to the non-inverting and inverting outputs of the second summing amplifier 4, an additional operational amplifier 32, the circuits of each of the two inputs of which include a series-connected additional resistor and a diode (24 and 26, 25 and 27) whose common point is the circuit of the first input is connected by The third 28 and fourth 29 diodes with the outputs of the first 20 and second 21 NAND logic elements, a common point between the additional resistor 25 and the diode 27 in the second input circuit of the operational amplifier 32 are connected through the fifth 30 and sixth 31 diodes with the outputs of the third 22 and the fourth 23 logical elements AND-NOT, the input of the node 11 forming the sign of the rotational speed, connected to the non-inverting output of the sensor 1, the EMF of the engine E, is connected to the inputs of the first 20 and third 22 logical elements AND-NOT, the input of the GT node, connected to the inverting output of the sensor 1 Uh Since the engine E is connected to the inputs of the second 21 and fourth 23 logical AND-NO elements, the input unit 11, Compound; with non-inverting in the front of the sensor 2 magnetic flux of the engine f, is connected to the inputs of the second 21 and third 22 logical elements AND-NOT, a. input node 11, connected to the inverting output

sensor 2 magnetic flux f engine, is connected to the inputs of the first 20 and fourth 23 logical elements AND-NOT.

A device for determining the frequency of rotation of a DC motor operates as follows.

The two inputs of the first summing amplifier 3 are supplied with opposite signs of voltage I) from the output of the source 5 of a constant voltage and proportional to the value. non-magnetic flux Φ of the motor voltage Kf-F.51dpF, where K is a scale factor, the Enaka constant of which is provided connected to the non-inverting and inverting outputs of magnetic flux sensor 2 and 7. The voltage value U is chosen not less than the maximum value The output voltage of sensor 2 is magnetic flux of the engine, so that the output voltage of the first summing amplifier 3, determined by the difference i-Kf-F-dF, always has a constant sign. it

5, the voltage is multiplied by the output voltage of the second summing amplifier 4 and is output from the multiplication unit 10 to the first input of the second summing amplifier 4,

0 to the second input of which the proportional emf of the motor E is the voltage -K E-signE, where the scale factor, the sign of which is provided by the diodes 8 and 9 connected to the non-inverting and inverting outputs of the sensor 1 of the emf.

When choosing resistors in the feedback circuit and in

0 circuits of the first and second inputs of the second summing amplifier in accordance with the conditions

G-2

 .

wasp

where Csu is the scale factor of the rotational speed;

k is the coefficient of the block of variable 10; Cc - constructive constant

engine; g, g - resistors resistance

in the feedback circuit, the first and second inputs of the amplifier, the corresponding output voltage of the second sum of the amplifier is determined by the expression

sig-nt

E-sigf E

and.

 C.g -Slgftiq UU Sigfr

From which it follows that the output voltage of the second sum of amplifier 4 is proportional to the engine rotational speed o), and the sign of this voltage differs from that of the engine rotational frequency due to the presence of an emf and magnetic flux ratio as a factor, i.e. to obtain at the output of the device a signal / sign of which corresponds to the sign of the rotation frequency of the engine, the output voltage of the second summing amplifier 4 must be multiplied by an amount opposite to the indicated ratio of the EMF signs and the magnetic flux of the engine at the rotational frequency sign II, which performs this function.

When the device is operating in the process of reducing the magnetic flux f of the motor, the voltage of the motor at the second input of the second summing amplifier 4 is simultaneously proportional to the EMF E sff, but the output voltage of the first summing amplifier 3 i dpF increases, which through the unit multiplying 10 enters the first input of the second summing amplifier 4 with the same sign as the voltage at its second input ... Similarly, as the magnetic flux increases, the voltage at the first input of the second sum decreases but increases (due to an increase in EMF) voltage at its second input, i.e. in drive control modes of the electric drive by varying the magnitude of the magnetic flux at the final values of the engine rotation frequency, the total input signal (and the feedback signal zi) with a wide range of variation of the magnetic flux, which provides an increase in the tyunost of determining the frequency of rotation of the engine. A change in the sign of the magnetic flux and the emf of the motor does not change the mode of operation of the second summing amplifier 4, the outputs of which in all modes preserve constant voltage signs (when the circuit of the device is executed in accordance with Fig. 1), the negative output of this amplifier remains the voltage is proportional to the value of | iff, and at its inverting output is a positive voltage proportional to the value of + tw (,

When the magnitude of the magnetic flux of the engine decreases, when the rotational speed of the engine is determined by the ratio of decreasing values of the EMF and magnetic flux and the influence of the error of the circuit elements increases, the relative determination of the rotational frequency from the output of the first summing amplifier 3 to the input of the multiplying unit 10 voltage U-Kd, i gn f increases, and in the area of high values of input voltages of multiplication unit 10, the relative error of signal multiplication decreases, which contributes to w tonosti determining engine speed. As the magnitude of the magnetic flux increases, the output voltage of the first summing amplifier 3 inputted to the interleaving unit 10 decreases, however, this reduces the influence of the accuracy of the multiplication unit 10 on the accuracy of determining the rotation frequency, as the output signal of the multiplier 10 decreases. to the first input of the second summing amplifier 4, as compared with a simultaneously increasing signal at the second input of the second summing amplifier, proportional to the increasing emf of the motor This resulted in a reduction in the effect of the output signal of the multiplication unit 10 on the total value of the input signals of the second summing amplifier, which determines the output voltage of this summing amplifier 4, which is proportional to the rotation frequency. Thus, the multiplier 10 operation mode in the proposed device improves the accuracy of determination engine rotational speeds with a wide range of magnetic flux variations.

In the presence of high-frequency interference, their effect on the operation of the device can be reduced to an acceptable value by the inclusion of a capacitor in the circuit. Reverse communication of the second summing amplifier 4.

The execution of the node II of forming the sign of the rotation frequency according to the scheme shown in FIG. 2, makes it possible to exclude a nonlinear analog converter from the channel of passage of the signal being detected and thereby exclude the influence of the instability of its characteristic on the accuracy of determining the rotation frequency. With the same signs of emf and motor magnetic flux, the sign of the output voltage of multiplier 12 is positive. At the same time, the diode 17 is open and the positive potential at its cathode closes the diode 15. The diode 18 is blocked by a positive potential at the output of the multiplication unit 12, and the positive voltage from the inverting output of the second summing amplifier 4 goes through diode 16 to the input of the operational amplifier 19, the output voltage which. is proportional to the engine speed, has

negative sign. With different signs of emf and motor magnetic flux, the output voltage of multiplier 12 is negative. In this case, diode 18. opens and a diode 16 is blocked at its anode with a negative potential, and diode 17 is blocked with a negative potential at the output of the unit 12 times, so that the negative voltage from the non-inverted output of the second summing amplifier 4 is fed through diode 15 to the input of the operational amplifier 19, the output voltage of which will then be proportional to the frequency of rotation of the engine with a positive sign. When the assembly 11 is executed in accordance with FIG. 2, the same signs of EMF and magnetic flux of the engine (i.e. one definite sign of the engine rotational speed) correspond to a negative voltage at the output of the operational amplifier 19, and consequently, at the outputs of the node 11 and the device as a whole, and to different signs of the EMF and magnetic flux the motor (i.e., another determined sign of the engine rotational speed) corresponds to a positive voltage at the indicated outputs; if necessary, the output signal signs are easily reversed if one of the inputs of the multiplication unit 12 is The key is not to neinvertiruyudemu and to the inverting output of the sensor I or EMF probe 2 of the magnetic flux of the engine.

The execution of the node II of forming the sign of the rotation frequency according to FIG. 3 completely eliminates the need for non-linear analog converters. The operation of the NAND logic elements 20, 21, 22, and 23 is determined by the fact that, with the same signs of emf and motor magnetic flux, the signs of the signals at the non-inverting outputs of the sensors

1 EMF and 2 magnetic flux of the engine are the same, and the signs of the signals at their inverting outputs are opposite to the previous ones and the same between themselves. On the other hand, with different signs of EMF and magnetic flux of the engine, the sign of the signal at the non-inverting output of the sensor 1 of the engine EMF coincides with the sign of the signal at the inverting output of the sensor 2 motor magnetic flux, and the sign of the signal at the inverting output of the sensor 1 is the motor emf coincides with the sign of the signal

on non-inverting sensor output

2 magnetic flux of the engine and the opposite sign of the previous signals. With the same signs of EMF and magnetic flux of the engine, the negative potentials formed at the outputs of the first 20 and second 21 logical elements are not

The diodes 28 and 29 are locked, so that the negative voltage from the inverting output of the second summing amplifier 4 goes through diode 26 to the input of the operational amplifier 32, the output voltage of which is proportional to the frequency of rotation of the engine and goes to the outputs of node II and the entire device with a positive sign corresponding to

specific direction of rotation

motor (diode 27 is locked with negative potential at its anode, coming through open diodes 30 and 31).

With different EMF signs and motor magnetic flux, the circuit works similarly, but diodes 30 and 31 are locked, and the positive voltage from the inverting output of the second from the pickup amplifier 4 is fed to the input of the operational amplifier 32 through the diode 27, providing a negative sign of the output signal of the operational amplifier 32, node And and the device as a whole, that

corresponds to the direction of engine rotation opposite to the previous case.

Thus, the proposed device for determining the frequency

engine rotation constant

provides an increase in the accuracy of determining this rotational speed with a wide range of variation of the magnetic flux of the engine and, unlike the known device, can be used both in electric drives with two-zone regulation and in electric drives with engine reversal by changing the sign of the magnetic flux, for example, in electric drives of transport and transport machines , excavators, mine hoists, rolling mills.

Claims (2)

1. An apparatus for determining the frequency of rotation of a direct current motor, comprising sensors for EMF and magnetic motor flux, two 0 summing amplifier, two diodes and a DC voltage source connected to the input of the first summing amplifier, characterized in that 5 to increase the accuracy of determining the rotational speed of the engine, the multiplication unit, two additional diodes and the node of the formation of the sign of the rotation frequency, and the EDB sensors are introduced into it. 0 and the magnetic flux of the engine and the second summing amplifier are made with inverting and non-inverting leads, and the outputs of the sensor of the magnetic flux of the engine through the first and second diodes are connected to the input of the first summing amplifier, whose output is through the multiplication unit, the second input of which is connected to the non-inverting output of the second summing amplifier, is connected to the first input of the second summing amplifier, the second input of which is connected through the third and fourth diodes to the outputs of the EMF sensor of the engine f and the outputs of the second summing amplifier connected to the inputs of the node forming the sign of the rotation frequency, the inputs of the task whose sign is connected to the outputs of the EMF sensors and the magnetic flux of the engine. 2. The device according to claim 1, characterized in that the node forming the sign of the motor rotation frequency is made in the form of a multiplication unit connected to the inputs of the task of the sign of this node, two additional resistors, four connected; pairwise counter-diodes, an additional opamp, in the circuits of each of the two inputs of which are connected a series-connected additional resistor and a diode, the common points between which through the third and fourth diodes are connected to the output of the multiplying unit of the specified node, 3, the device according to claim 1, characterized in that the node forming the sign of the rotation frequency is made in the form of four logical elements AND-NOT, two additional resistors, six diodes and connected between the output of the specified node and its inputs connected to the non-inverting and inverting outputs of the second summing amplifier, additional opamp, in each circuit Two inputs of which are connected; successively an additional cutter and a diode, whose common point in the first input circuit is connected through the third and fourth diodes b of the first and second I-NE logic elements connected to the first diode, the common point between the additional resistor and the diode in the second circuit O the opamp is connected via the fifth and sixth diodes connected to the second diode with the outputs of the third and fourth logic elements AND –NE, the input of the rotational speed sign, connected to the non-inverting output of the motor EMF sensor, is connected to the inputs of the first and third logical elements AND NOT, the fToro input of the node, connected to the inverting output of the motor EMF sensor, is connected to the inputs of the second and fourth NAND logic elements, the input of the specified node, connected to the non-inverting output of the sensors Single magnetic flux motor is connected to the inputs of second and third logic AND-NO elements, and the node input coupled to the output invertiruihtsi .m magnetic flux sensor of the engine, connected to the inputs of first and fourth logic AND-NO elements. Sources of information taken into account in the examination 1.Garnov V.K. and others. The unified system of autorun electric drive in metallurgy. M., Metallurgists, 1971, p. 182. 2. USSR Author's Certificate for Application No. 2346342/07, cl. H 02 R 5/00, 1976. v3