SU488298A1 - Device for controlling the speed of two DC motors - Google Patents

Description

one

The invention relates to the field of electrical engineering and can be used, for example, in electric vehicles.

A device for controlling the speed of two DC electric motors is known, which contains two parallel circuits of serially connected windings of the core and excitation and thyristors, in parallel with which are connected electrical valves, chokes and capacitors, and also a thyristor, the power electrodes of which are connected to the same power electrodes of these thyristors and resistor.

However, in such devices there is a complex circuit design and not full use of the installed capacity of the switching elements.

G in order to increase reliability and provide electric braking in the proposed device between the connecting points of the commutating chokes and capacitors included an additional capacitor and a resistor connected between the connecting points of the windings of the core and the excitation of electric motors.

FIG. 1 is a circuit diagram of the device described; in fig. 2 is a voltage chart for each of the electric motors.

The device is connected via the switching contact element 1 to the positive pole of the power source.

Thyristors 2 and 3 connect excitation windings 4 and 5, measles 6 and 7 of electric motors shunted by opposing valves 8 and 9, to a power source.

A thyristor 10, the power electrodes of which are connected to the same power electrodes of thyristors 2 and 3, connects the electric motors in series to a power source.

The thyristors 2, 3 and 10 are switched by capacitors 11 and 12, which are recharged through the chokes 13 and 14 and the thyristors 15 and 16, the suppressing thyristors 17 and 18, and the capacitor 19 connected between the junction points of the capacitor 11 and the throttle 13, of the capacitor 12 and drossel 14.

The capacitors And, 12 and 19 are connected to the power source through the valves 20 and 21.

Through the switching contact element 22, the current limiting braking resistor 23 is connected between the points of connection of the field windings with the motor cores.

In order to implement the regenerative braking mode, an electric valve 24 is turned on counter-parallel to the switching element 1.

The device works as follows.

When the contact closes capacitors

11, 12 and 19 are charged from the power source to voltages inversely proportional to the magnitude of their capacitances.

When the quenching thyristors 17 and 18 are turned on, the capacitors 11 and 12 are recharged from the power source to the magnitude of its voltage, and the capacitor 19 is recharged, along the circuits:

for the capacitor 11, 1, 20, 11, 13, 17, 4, 6; for capacitor 12, 1, 7, 5, 18, 14, 12, 21; for condenser 19, 1, 7, 5, 18, 14, 19, 13, 17, 4, 6; in the polarity indicated in FIG. 1 without brackets.

With the thyristor 10 turned on, the electric motors are connected to the power supply sequentially.

For the PREPARATION of the switching elements, thyristors 15 and 16 are included in the thyristor 10 suppression. The capacitors are recharged along the following circuits: for capacitors 11, 11, 15, 13; for capacitor 12, 12, 14, 16; for capacitor 19, 1, 20, 15, 13, 19, 14, 16, 21 in the polarity indicated in FIG. 1 in brackets. After the recharge of the capacitors has been completed, the switching elements are ready for the thyristor to be quenched 10.

When turning on, the suppressing thyristors 17 and 18 apply a blocking voltage to the thyristor 10 and it restores its blocking properties, after which the capacitors 11, 12 and 19 are recharged in polarity indicated in FIG. 1 without brackets.

Further, the processes are repeated.

By changing the time shift of the pulses applied to the control electrode of the thyristor 10, in relation to the pulses applied to the control electrodes of the extinguishing thyristors 17 and 18, the average voltage on each of the motors ranges from some minimum to some maximum, approximately equal to half the voltage of the power source (f: ig. 2).

If during the operation of the device the load current exceeds a predetermined maximum value, i.e., the time of action of the blocking voltage on the thyristor 10 is insufficient to restore its blocking properties, then the capacitor 19 discharges almost to zero, and the capacitors 11 and 12 charge dc from the power source to half its voltage in polarity indicated in fig. 1 without brackets. When the thyristors 15 and 16 are turned on, capacitors 11 and 12 will recharge and oscillating charge of capacitor 19 to a voltage of approximately twice the supply voltage (polarity of the voltage is shown in brackets in Fig. 1). When the thyristors 17 and 18 are turned on, the blocking voltage of capacitors I, 12 and 19 will again and again be applied to the thyristor 10. When the load current decreases to the calculated value, the device’s operation at this

stage is restored. Thus, fluctuations in the load current, which are characteristic of the working conditions, for example, traction electric motors, do not lead to a malfunction of the device when the load current exceeds a predetermined value.

If it is necessary to further increase the voltage on the electric motors, and hence their speed, after reaching the half voltage of the power source, control pulses are applied to thyristors 2 and 3.

At the same time, the time shift of the pulses supplied to the control electrodes of thyristors 2 and 3 with respect to the pulses applied to the control electrodes of thyristors 17 and 18 provides an average voltage on each of the motors not exceeding half the voltage of the power source.

At this stage of operation, the switching devices of thyristors 2 and 3 are similar to the switching of thyristor 10 and are described earlier.

By changing the time shift of the pulses applied to the control electrodes of thyristors 2 and 3, with respect to the pulses applied to the control electrodes of thyristors 17 and 18, the average voltage on each of the motors ranges from half the voltage of the power source to maximum equal to the voltage of the power source (Fig. 2). In order to implement the electric braking mode of the electric motors, the switching contact element 1 is opened and the element 22 is closed. By this switching, when switching the thyristors of the device, the electric motors are transferred to the generating mode. The load of the generators is the current limiting braking resistor 23 when the thyristors 2 and 3 are turned on, and in the period of their off and thyristor 10 turned on - the power source,

for example, a battery. Energy recovery occurs along chains 6, 23, 22, 7, 24.

The operation of the switching elements of the device in this mode is similar to their operation in the motor mode with the difference that the electric motors become the source of energy.

To increase the reliability of the switching elements in the electric braking mode, it is possible to connect the electric valve 20 directly to the power source in front of the switching contact element 1.

The subject matter of the invention

Speed control device

two DC motors containing two parallel circuits of series-connected windings of the core and excitation and thyristors, in parallel with which are connected switching electric valves, chokes and capacitors, as well as a thyristor, the power electrodes of which are connected to the same power electrodes of these thyristors, and a resistor that differs in order to increase reliably6

To maintain and provide electrical braking, it is equipped with a dololnitelny capacitor connected between the points of connection of the mentioned commutating chokes and capacitors, and a resistor is connected between the points of connection of the windings of the core and the excitation of electric motors.

Pete

UCP - /

tO

Pete