RU1791904C - Nonreversible electric machine with rectifier-mechanical commutator - Google Patents

Abstract

Usage: electric machines with valve-mechanical switching. SUMMARY OF THE INVENTION: A correction unit is introduced into the control system of the machine, which creates the effect of shifting the sliding contacts in the direction of rotation of the core, which compensates for the demagnetizing response of the core and eliminates the compensation winding. 5 ill.

Description

The invention relates to electrical machines, in particular DC machines with additional devices for improving switching.

A known electric machine with a fan-mechanical commutator (VMC), comprising a mechanical collector, groups of brushes in contact with it, connected to power supply terminals through controlled semiconductor valves. In this machine, switching is carried out without additional poles using capacitive electric energy storage devices.

A disadvantage of such a machine is its complexity.

An electric machine with a valve-mechanical switch is also known, comprising a mechanical collector, diverse groups of brushes in contact with it, connected to the power supply terminals through thyristor key elements, a switching unit, a control circuit consisting of a pulse-phase control system, a key block, logic block, position sensor and tachogenerator.

This machine is the closest to the invention in terms of technical nature and the achieved result. Like most collector machines with difficult operating conditions, it uses a compensation winding, which significantly increases the reliability of their work, but at the same time complicates the design and increases complexity. In machines without a compensation winding, with a saturated magnetic system and brushes mounted on the neutral side, the transverse reaction along with distortion of the main magnetic field has a noticeable demagnetizing effect on it. When the brushes shift from neutral in the direction of rotation of the engine, along with the transverse side, a longitudinal magnetizing component of the reaction occurs. However shift

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brushes in the direction of rotation of the core in reversible motors of a traditional design are not allowed due to switching considerations. In addition, when the direction of rotation of the engine changes, the longitudinal component of the core response becomes demagnetizing, which reduces the stability of the electric drive when the magnetic flux is weakened. In machines with a high-frequency magnetic oscillator, due to the controlled switching by means of thyristors, with rigidly installed brushes along the line of geometric neutral, it is possible to provide the effect of their shift in the direction of rotation of the core using electronic means. Thereby, the conditions are provided for creating a machine with high-power high-speed magnetic circuit without a compensation winding, characterized by high switching reliability, overload capacity and stability when the magnetic flux is weakened.

The purpose of the invention is to simplify the design of a machine with a VMC, due to the possibility of creating it without a compensation winding while maintaining high switching and overload characteristics.

This goal is achieved in that. the control circuit includes a correction unit consisting of two pulse shapers, an operational amplifier with inverting and non-inverting inputs, a functional converter, a capacitor, a key on two transistors, an inverter, two two-input logic elements NAND, and the inputs of the pulse shapers are connected to the outputs position sensor, the outputs are combined and connected to the non-inverting input of the operational amplifier, to which the tachogenerator output is also connected via a functional converter, a pair A capacitor is connected to the inverting input of the operational amplifier, connected through resistors to the output of the tachogenerator, and also to the output of the operational amplifier through a key, while the output of the operational amplifier is connected to the input of the inverter, the output of which is connected to the first inputs of the NAND gates, the second inputs of which are connected to the outputs of the position sensor, and the outputs are connected to the inputs of the logic unit.

The use in the control circuit of a correction unit connected between the outputs of the position sensor and the input of the logic unit allows applying control pulses to turn on the thyristors of the bridge circuits with some time delay At relative to the signals of the position sensor. Studies have shown that if the specified delay is changed by law

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then the motor creates the effect of a shift of the sliding contacts in the direction of rotation of the core (yz is some non-linear

function; n is the rotational speed of the machine). When working with a delay A t in the engine with a high-frequency motor, magnetizing ampere-turns of the longitudinal reaction core F ad are created, which compensate for the demagnetizing

ampere-turns of the transverse reaction core R p. . Compensation windings are no longer needed. A more detailed justification of the physical meaning of expression (1), taking into account the parameters of the block

corrections and machines are given below.

In FIG. 1 is a schematic diagram of a machine with a VMC with the number of conductive collector plates K2 22; in FIG. 2 is a functional block diagram of a machine with a control block diagram; in FIG. 3 is a simplified diagram of a correction block; in FIG. 4 is a schematic diagram of a correction block; in FIG. 5 is a diagram of control signals and thyristor currents of bridge circuits.

The machine contains a core winding 1 connected to a mechanical collector 2 containing conductive plates 3-24 and the same number of insulating plates in contact with them are bipolar

groups of brushes 25-28 connected to the positive and negative terminals of two bridge circuits on thyristors 29-40. The machine also contains current transformers 41, uncontrolled rectifier 42 dl

powering the winding of the additional poles 43. The control circuit 44 (Fig. 2) contains a pulse-phase control system (SIFU) 45, the inputs of which are supplied with synchronization signals UCUHX., control Uy

and a switching signal Up from the logic block (BL) 46. Switching the control pulses of the thyristors 29-34 of the bridge circuit to the set of thyristors 35-40 is provided by the key block (BCL) 47. The inputs of the logic block

(BL) is connected to the position sensor (DP) 48 through the correction unit (BKR) 49, which also receives a signal from the technical generator (TG) 50.

The correction block (Fig. 3) consists of two

pulse shapers 51.52, the outputs of which are connected to the non-inverse input of the operational amplifier 53, which also supplies the voltage of the tachogenerator through a functional converter 54. The inverting input of the amplifier is connected to a capacitor 55 connected through resistors 56, 57 to the output of the tachogenerator and to the output of the operational amplifier through the key transistors 58, 59. At the same time, the output of the amplifier through the inverter 60 is connected to the inputs of two logical elements AND-NOT 61.62.

When the machine is operating, the sliding contacts move from the working surface of the collector from left to right (Fig. 2). Until time ti, thyristors 29, 34 are in the conducting state. The core current 1a flows from phase A through thyristor 29, terminal 25, plate 3, through parallel branches of core winding, collector plate 14, terminal 28, thyristor 34 to phase C. Thanks to current transformers 41 and rectifier 42, a constant current equal to the cor current flows through the winding of the additional poles 43. At time ti, when the sliding contacts occupy the position shown in FIG. 1, a positive pulse appears in the channel B1 of the position sensor 48 (Fig. 2, 5). Passing through the correction block 44, which provides a time delay At, the same signal, but already at time t.2 through the channel Us, enters the input of the logic block 46. Further, in the logic block, according to the well-known principles, the signal Up becomes zero for the time r0 ( Fig. 5), during which the preparation of the SI FU formers takes place for issuing the next control pulses. At time g3, an enable signal appears in channel B2 at channel B2 (Fig. 5), thanks to which control signals are transmitted in channels 47 through channels 35-40 (Uss, Uad in Fig. 5). of thyristors 35 and 40 in switching sections connected to collector plates 3.4 and 14.15 under the influence of switching EMF from a stream of additional poles, the forward current of thyristors 29 and 34 (i25, iae) decreases, and in thyristors 35 and 40 is growing. After the time tK has elapsed, the thyristors 29, 34 are turned off, the current reversal is completed in the switched sections, and the total current cor la flows through the thyristors 35.40 and the contacts 26.27. The movement of the 25.28 contacts from the conductive plates to the insulating ones occurs in a de-energized state without sparking.

With further movement of the contacts along the collector at time ts, similar processes occur in sections associated with plates 4,5 and 15,16 in which the switching process ends

by turning on the thyristors 29, 34 and the flow of core current through the contacts 25, 28. Next, the processes are repeated.

The correction unit, designed to provide a time delay A t Y2 / l, operates as follows. Until time ti, the transistor switches of the drivers 51, 52 (Fig. 3, Fig. 4) are in the open state. The voltage Ua at the non-inverting input of the operational amplifier 53, as well as at its output DI, has a positive polarity (Fig. 5). The key transistor 58 is open, and the voltage across the capacitor 55 is zero. After the appearance of the shaper 51 at the input and at the moment of positive pulse B1, the transistor switch is turned off and the negative voltage pulse is fed through direct input 53 through C1 and V3. At the same time, at its output and, accordingly, at the input, due to the positive feedback In addition, a negative voltage pulse 1) 22 appears (Fig. 5). The magnitude of this voltage, taking into account the signal from the functional converter 54, is determined as follows

U22 Ui-Uir Ri4 Re / (Ri3 Rs} Rs / (Rs + Re), (2)

where Ui is the voltage at the output 53 of negative polarity. Simultaneously with the switching of the operational amplifier, the transistor 59 opens, 58 closes and the charge of the capacitor 55 begins with the voltage of the tachogenerator, which is defined as follows:

Utr br n

(3)

where bi is the coefficient of proportionality. The voltage across the capacitor increases linearly over time A t, if At «r (Rn + Ri2) Ck, and is determined by the following relationship:

Uc UTrAt / r

(4)

When this voltage reaches U22 at non-inverting input 53, i.e.

Uc U22,

(5)

then the voltage at the output Ui and, accordingly, at the input 53 changes polarity again and becomes equal to 1) 21 (Fig. 5). The voltage pulses Ui from output 53 are converted, thanks to the inverter 60 and the NAND gate 61, to signals Us, which are then fed to the input of logic block 46. From the joint solution of equations (2) - (5), we can determine the dependence of the delay time At, which created by the correction unit.

Claims (1)

At 1) 22 r / UTr U22 r / () yg / n (6) Claims A non-reversible electric machine with a valve-mechanical switch, containing a mechanical collector, heterogeneous groups of brushes in contact with it, connected to the power supply terminals through thyristor key elements, a switching block containing current transformers, a rectifier and additional poles with windings, a control circuit, comprising a pulse phase control system, a key block, a logic block, a position sensor with two outputs and a tachogenerator, characterized in that, for simplicity, the control circuit neither contains a correction unit, consisting of two pulse shapers, an operational amplifier with inverting and non-inverting inputs, a functional a converter, a capacitor, a resistor, two key transistors, an inverter, two two-input NAND gate elements, the inputs of the pulse shapers connected to the outputs of the position sensor, the outputs combined and connected to the non-inverting input of the operational amplifier, to which the tacho output is connected via a functional converter generator, to the inverting input of the operational amplifier is connected the first output of the capacitor, connected through a resistor to the output of the tachogenerator, the second output of which is connected to a ground terminal of the control system, and a resistor connected through the first key transistor to the output of the tachogenerator, and through the second key transistor to the ground terminal of the control system, the output of the operational amplifier is connected to the control input of the key transistors and the input of the inverter, the output of which is connected to the first inputs of AND-NOT gates, the second inputs of which are connected to the outputs of the position sensor, and the outputs are connected to the inputs of the logic unit. - / Ue --- i-- | 45 i RIF G silt 47  L / f / 7 i - j g-y} ---- th / , 57 x-L.:., I  -) r 14-r L / f / 7 i - - j th / i -I -, L. ™ ..-, V --- - OOI / / A  I o1-- and. tdli AT -4rJn  j I i hpiaJ i. GI Esetbl- / ttf. / N, ix J.t - - t L   GI -t i / ttf. / N, ix