RU2375811C1 - Direct current motor control device - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention refers to the field of electric engineering and can be used for direct current electric motor control. Direct current motor control device contains power supply unit, filter, inverter, auxiliaries load, current sensor, pulse transformer with two additionally introduced windings, each of them with two identical parts, four power switches, two capacitive storages and load control unit. Aforesaid elements are interconnected in such a way as pointed out in application materials.

EFFECT: functionality enhancement and increase I reliability of direct current motor control device.

5 dwg

Description

The invention relates to electrical engineering and can be used primarily for controlling DC motors.

A device for controlling a DC motor is known, in which the energy of switching losses during engine braking is used to power the motor excitation winding (RF patent No. 2111161).

The closest in technical essence to the claimed device is a current control system with counter-EMF (RF patent No. 2079204), containing a power source, a series-connected filter and a standalone inverter, auxiliary load connected to an additional winding of a pulse transformer, synchronizer, control unit, two keys connected by power leads to the output winding of a pulse transformer, two switches, two additional power supplies, current sensor, load with counter-EMF, generator mpulsov.

The disadvantages of the known device selected as a prototype are:

1. Turning the inverter on and off when turning on and off the recovery mode occurs without synchronization with the switching period of the inverter transistors, which can lead to the magnetization of the transformer core and, accordingly, to current overload in the inverter and a decrease in reliability.

2. If a DC motor is used as the load, reverse is not possible, which limits the functionality of the device.

3. The keys switching the load operate with a frequency half that of the inverter keys, and the dynamic losses are proportional to the supply voltage and switching frequency. In the case of applying a high-voltage load, to reduce losses, it will be necessary to reduce the switching frequency of the high-voltage switches and, accordingly, the switching frequency of the inverter keys, which will lead to an increase in the dimensions of the inverter transformer, and this narrows the scope of the device.

The aim of the proposed invention is to expand the functionality and increase the reliability of the control device of the DC motor.

This goal is achieved by the fact that in the control device for a DC motor containing a power source, a filter, an inverter connected to the primary winding of a pulse transformer, another winding of a pulse transformer connected to an auxiliary load, a current sensor according to the invention additionally introduced the first and second pulse windings transformer, each consisting of two identical parts, four power switches, two capacitive drives and a load control unit, the first and second the outputs of the first and second windings are connected to the first power terminals of the first, second, third and fourth switches, the second terminals of which are connected to each other and to the first terminal of the current sensor, the second terminal of which is connected to the first terminal of the load, the second terminal of which is connected to the first power terminals of the fifth and the sixth key, the second terminals of which are connected to the middle terminals of the first and second windings of the pulse transformer, which are also connected to the first power terminals of the first and second bilateral keys, the second terminal the odes of which are connected respectively to the first outputs of the first and second capacitive drives, the second outputs of which are connected to each other and the first output of the current sensor, the control outputs of the first, second, third, fourth, fifth and sixth keys are connected to the corresponding outputs of the first driver, the input of which is connected to the first output of the load control unit, the second output of which is connected to the input of the second driver, the output of which is connected to the control input of the inverter, the third and fourth outputs of the control unit manual ultrasonic inspection are connected to the control inputs of the first and second double-sided keys, the first and second inputs of the load control unit connected to the first and second terminals of the current sensor, a third input of the load control unit connected to the second load terminal.

In the inventive device, all the features included in the distinctive part of the formula are used individually for their intended purpose. However, their combination in this relationship ensures the achievement of a new technical result - the degree of reliability of the device and its functionality that are unknown from the prior art (devices of similar purpose), namely:

1) due to the fact that the switching frequency of the power switches does not depend on the operating frequency of the inverter, therefore, it is possible to use a device for controlling a DC motor with a high operating voltage, which expands the scope of its application;

2) the engine reversal mode is introduced, which also extends the functionality of the device;

3) due to the synchronization of the moment of switching the power switches and the moment of switching the inverter, this ensures a full cycle of the magnetization reversal of the transformer core, eliminates the current overload of the inverter associated with the magnetization of the core and increases reliability;

4) the energy accumulated in capacitive storage is used in acceleration and reverse modes, which reduces losses in the inverter, since at that moment it is turned off. This reduces the overall loss in the device, therefore, increases reliability.

Figure 1 presents the General diagram of the inventive device, figure 2 is an equivalent diagram of the device in acceleration mode, figure 3 is a diagram of the switching device in switching mode,

figure 4 is an equivalent circuit of the device in the recovery mode, figure 5 is an equivalent circuit of electrodynamic braking.

The control device for the DC motor contains a power source 1, for example a battery, through a capacitor filter 2 connected to the input of the inverter 3, which can be performed, for example, by a bridge circuit using field-effect transistors.

The inverter 3 is connected to the primary winding 4 of the transformer 5, the winding 6 of which is connected to the auxiliary load 7, which can be a power source for the device control circuit.

The inverter 3 is controlled by the load control unit (BUN) 8 through the driver 9, which generates control pulses for the transistors of the inverter 3.

The winding 10 of the transformer 5, consisting of two windings with the same number of turns, is connected to the first power output of the key 11 with an integrated reverse diode, for example, an M2TKI-200-12 insulated gate bipolar transistor.

The second power output of the key 11 is connected to the first output of the load 12, for example, a DC motor with independent excitation and the first output of the key 13, the second output of which is connected to the middle terminal of the winding 14 of the transformer 5.

The beginning and end of the winding 14 are connected to the first terminals of the keys 15 and 16, the second terminals of which are connected to each other and to the first terminals of the keys 17 and 18, as well as to the first output of the current sensor 19. The current sensor can be made in the form of a shunt, which is the second output connected to a second load terminal. The control outputs of the keys 11, 13, 15, 16, 17, 18 are connected to the outputs of the second driver 20, which generates the key control signals in accordance with the signals from the BUN. The findings of the current sensor 19 and the load 20 are also connected to the inputs of the BUN, in which the processing of feedback signals for current and voltage at the load.

The middle terminals of the windings 10 and 14 are also connected to the first power terminals of the bilateral keys 21 and 22, respectively, made, for example, on semiconductor relays. The control terminals of the bilateral keys 21 and 22 are connected to the outputs of the BUN, the second power terminals of which are connected to the terminals of the capacitive drives 23 and 24, made, for example, in the form of capacitor banks.

The device operates as follows.

Let at the initial moment of time the anchor of the DC motor be stationary. Consider the acceleration mode to a steady angular velocity.

When a pulse control signal is supplied from the BUN to the key driver 20, the key 11 closes with a delay τ, which is determined by the BUN (Fig. 3). The inverter 3 is turned on, the voltage U appears on the winding 10 of the pulse transformer, which through the diodes of the open keys 17 and 18 is supplied to the load with the counter-EMF 12, for example, a DC motor with an independent voltage.

In this case, the motor current is closed in the circuit: diodes of the keys 17, 18, the winding 10 of the transformer, the closed key 11, the motor armature, the current sensor 19, the diodes of the keys 17 and 18 (figure 2).

When the motor current reaches the set maximum value according to the signal from the BUN, the inverter 3 is turned off, while the turn-off moment is synchronized with the switching period of the keys of the inverter 3 in such a way as to ensure a complete remagnetization cycle of the transformer core.

The motor current is closed in a circuit: winding 10 of transformer 5, diodes of keys 17, 18, closed key 11, load 12, current sensor 19 (Fig. 2), due to the fact that half of the winding 10 have the same number of turns and are turned on counter, the magnetization of the core of the transformer is excluded.

Further, the switching process of the inverter 3 continues, while the key 11 is closed continuously, which significantly reduces dynamic losses and increases the reliability of the device.

In this mode, the average motor current is determined by the current limiting circuit included in the BUN 8 unit; in acceleration mode, the device acts as a stabilizer of the motor current, after acceleration in steady state is completed, the angular velocity of the motor is determined as

W = (U * t _and / TI * R) / Ce,

where U is the voltage across the winding 10 or 14 depending on a given direction of rotation,

I is the motor current,

R is the resistance of the engine armature,

Ce is the structural constant of the engine,

T - pulse width

modulation (PWM);

ti is the inverter turn-on time for period T.

In accordance with this, the motor voltage, and hence the angular velocity, is determined by the ratio ti / T, the motor current is determined by the value of the moment of resistance to rotation, while in the control mode the keys 11 and 13 operate with a PWM frequency, which is several kilohertz, while the operating frequency inverter 3 is several tens of kilohertz, which significantly reduces losses in the device and increases reliability, since the losses on the keys are proportional to the switching frequency and the switched voltage.

The braking mode of the engine armature is as follows.

In this mode, the inverter 3 is turned off by a signal from the BUN, and there are two possible ways of braking the motor: regenerative and electrodynamic in accordance with the control signals from the BUN. During regenerative braking, the EMF of the motor closes through the diode of the open key 11, two halves of the winding 10, the keys 17 and 18, the current sensor 19, the second output of the motor, while the keys 17 and 18 are closed and open in antiphase with the switching frequency of the inverter 3, on the winding 6 there is a voltage that is used to power the load of own needs 7 (figure 4).

The braking time is determined by the average motor current at the time of braking, which is set by the BUN in accordance with the signal of the current sensor 19, while the braking time determines the switching time of the keys 17, 18 and is several seconds, so the losses in the keys 17 and 18 are minimal.

When the electrodynamic method of braking (figure 5), the keys 11, 15-18 are open, while the motor EMF is closed through a closed key 13, two halves of the winding 14, diodes open keys 15 and 16, a current sensor 19, the motor armature. The self-induction voltage that occurs on the inductance of the motor armature at the moment of opening of the key 13 is closed through the diode of the open key 11, the closed key 21, the capacitive storage 23 and the current sensor 19.

The magnitude of the braking current of the engine, and therefore the braking time is determined by the BUN, while the rotation energy of the engine is accumulated in the drive 23 and is determined as

W _n = ((U ₁ ) ^ 2- (U ₀ ) ^ 2) * C / 2,

where U ₀ - the initial value of the voltage on the drive until the start of braking;

U ₁ - the value of the voltage on the drive at the end of the braking interval;

C is the capacity of the drive.

Similarly, electrodynamic braking occurs when the motor armature rotates in the opposite direction, while the EMF closes in the circuit: current sensor 19, open-key diodes 17, 18, transformer 5 winding 10, closed key 11, motor armature 12.

When the key 11 is opened, the motor current flows along the circuit: motor armature 12, current sensor 19, drive 24, closed key 22, motor armature, while the charge of drive 24 occurs.

The energy accumulated in the drives 23 and 24 is used in acceleration mode, while the inverter 3 is turned off by the control signal from the BUN, and the keys 21 or 22 are turned on by the signal from the BUN 8 depending on the specified direction of rotation of the motor shaft, and the voltage to the motor comes from the drive 23 or 24, respectively, and the power from the source 1 is not consumed, which increases the efficiency of the device.

The engine reverse mode consists of a braking mode and subsequent acceleration in accordance with the direction of rotation set by the BUN.

Prototypes of the claimed device have confirmed the achievement specified in the description of the technical result.

Claims (1)

A DC motor control device comprising a power source, a filter, an inverter connected to the primary winding of a pulse transformer, another winding of a pulse transformer connected to an auxiliary load, a current sensor, characterized in that the first and second windings of the pulse transformer are additionally introduced into it, each consisting of two identical parts, four power switches, two capacitive storage devices and a load control unit, while the first and second conclusions of the first and second windings are inens with the first power terminals of the first, second, third and fourth keys, the second terminals of which are connected to each other and with the first terminal of the current sensor, the second terminal of which is connected to the first terminal of the load, the second terminal of which is connected to the first power terminals of the fifth and sixth keys, second the terminals of which are connected to the middle terminals of the first and second windings of a pulse transformer, which are also connected to the first power terminals of the first and second bilateral keys, the second terminals of which are connected respectively Together with the first conclusions of the first and second capacitive drives, the second conclusions of which are connected to each other and the first output of the current sensor, the control conclusions of the first, second, third, fourth, fifth and sixth keys are connected to the corresponding outputs of the first driver, the input of which is connected to the first output of the unit load control, the second output of which is connected to the input of the second driver, the output of which is connected to the control input of the inverter, the third and fourth outputs of the load control unit are connected to the inputs of the control Lenia first and second double-sided keys, the first and second inputs of the load control unit connected to the first and second terminals of the current sensor, the third load control input of unit connected to the second load terminal.

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