SU1762377A1 - Dc electric drive - Google Patents

Abstract

Usage: In the electric drives of the Entity, due to the introduction of an additional switching element 9, storage capacitor 12, diode 10, resistor 11, as well as the time of the driving capacitor 13 and resistor 14, the dynamic braking thyristor 8 is delayed by the time required to turn off the power thyristor 2 1 sludge

Description

The invention relates to electrical engineering. namely, electric drives of constant current.

A device for controlling the frequency of rotation of DC motors.

The disadvantage of this device is the presence of contact elements in the power circuits of the engine, which significantly increases the dimensions of the device, its mass and reduces its reliability, in addition, such a device does not allow it to be controlled using contactless devices.

The closest in technical essence to the claimed device is a direct current electric drive selected as a prototype, containing a power source, a power thyristor, a motor whose armature is connected to a power source through this power thyristor, the control circuit of which is connected via a switching element to the power supply bus, as well as a thyristor for dynamic braking and its control circuit.

The disadvantage of this device is that the dynamic braking thyristor can turn on at any time when the control button is pressed. In this case, cases of turning on this thyristor at the most unfavorable moment when the power dash of the electric motor is in a conductive state are not excluded

those. at the beginning of the half-cycle you have a direct voltage applied to the armature. Since the power thyristor switch can go into the locked state when the control signal is removed only at the beginning of the half-cycle following the half-period in which the command to turn off the motor power is issued, when the dynamic braking thyristor is turned on in the half-cycle, when the power thyristor is in the on state, the circuit appears the passage of current from the power source through the circuit: bus positive voltage - power thyristor thyristor dynamic braking bus negative voltage of the source. This causes a short circuit of the power source and the failure of the drive element.

The aim of the invention is to increase the reliability of the electric drive.

The goal is achieved by that. that in the device containing the power source, the power thyristor, the motor, the armature of which is connected to the power source through this power thyristor, the control circuit of which is connected via the switching element to the power supply bus, as well as the dynamic braking thyristor and its control circuit are additionally introduced a second a switching element, a resistor and a diode of the charging circuit connected by the anode of the diode to the bus of the positive voltage of the rectifier, and a resistor to the make contact of the second Ί 0 switching element, two the capacitor and the timing, two resistors are timing and leakage, and one of the capacitor plates and one output of the leakage resistor are connected to the 15 bus of the negative voltage of the rectifier, the second cover of the storage capacitor is connected to the movable contact of the second switching element, the breaking contact of which is connected through a timing resistor to the connection point of the second terminal of the leakage resistor, the second plate of the timing capacitor and the control terminal of the dynamic brake thyristor eniya.

The introduction of additional elements made it possible to delay the turn on of the dynamic braking thyristor relative to the moment the stop command was issued for a time sufficient for 30 to turn off the power thyristor operating in the key mode and switching the voltage supplying the armature winding of the electric motor.

The drawing shows a variant of the circuit 35 of the electric drive, corresponding to the present description.

The device contains an electric motor

1. which is connected through a power thyristor 2 to a rectifier 3. Power thyristor 40 2 includes a control circuit 4 and a first switching element 5. Anchor winding of an electric motor 1 is shunted by a diode 6, the cathode of which is connected to the junction point of the power thyristor cathode. 45 of the first output of the armature winding of the electric motor and the first output of the current-limiting resistor 7, through which the point is connected to the anode of the thyristor of dynamic braking 8. The anode 50 of the diode .6 is connected to the second output of the armature winding of the motor and combined with the cathode of the thyristor of dynamic braking 8 are connected to the negative voltage bus rectifier 3.

In addition, the device contains a second switching element 9, as well as a charging circuit consisting of a series-connected diode 10 of the resistor 11. By the anode of the diode 10 is connected to the positive voltage bus of the rectifier 3. g the second output of the resistor to the normally open contact of the second switching element 9, and cumulative 12 and timing 13 capacitors, timing 14 and leakage 15 resistors, and one plate of the capacitors and one terminal of the leakage resistor 15 are connected to the negative voltage bus of the rectifier 3.

The device operates as follows. On command, the contact opens the first switching element 5, the power thyristor 2 is turned on and power is supplied to the armature winding of the electric motor 1, the armature comes into rotation.

In this case, the contacts of the second switching element 9 are transferred simultaneously with the contacts of the first switching element 5 being opened. The storage capacitor 12 is charged along the circuit: rectifier positive voltage bus 3 - charging circuit diode 10, resistor 11, closed contacts of the second switching element 9 of the capacitor plate 12.

The frequency of rotation of the armature is determined by the control circuit 4.

On the stop command, the contact of the first switching element 5 is closed and the contacts of the second switching element 9 are switched over. The storage capacitor 12 is connected via the normally closed contact of the second switching element 9, the time-setting resistor 14 to the time-setting capacitor 13 and the leakage resistor 15. The capacitors 12 and 13 are recharged. In this case, the voltage across the capacitor 13 increases in time according to the law determined by the time constant of the circuit, consisting of a resistor 14 and a capacitor 13.

Unlocking of the thyristor of dynamic braking occurs with a delay of at least 1, 5 half-periods of the supply voltage relative to the moment the stop command is issued. During this time, the power thyristor 2 manages to reliably go into a non-conductive state. In this case, the nominal values of the additionally introduced elements are determined by the following relations.

incl.

Rep _; J2

Rap

Cf. Snack. ⁼ 'jap. _r

Snack

R _yT . = (3 ... 5) · 10 ³ m.

where ^{_ the} amplitude value of the rectified voltage. IN;

1incl. - turn-on current of the dynamic braking thyristor, A:

W Rb _P. - resistance time of the driving resistor;

Cf. ^_ capacitance of the timing capacitor;

R _yT . - resistance of the leakage resistor. 15 ohms;

R ₃ ap. “Resistance of the charging resistor, Ohm;

Τι. Tg, T3 are time parameters at which the normal functioning of the device is ensured.

Claims (1)

Claim A direct current drive containing an electric motor, the armature winding of which is shunted by a reverse diode and 25 is connected via one output to a positive bus through a thyristor and the second to a rectifier's negative voltage bus, a dynamic braking thyristor, whose anode is connected through a current-limiting resistor to the junction point of the power cathode thyristor and motor armature, the cathode - to the bus of the negative voltage of the rectifier, the control circuit of the power thyristor and 35 first switching element, under for prison parallel control terminals and power terminals of the thyristor control circuit, wherein. that, in order to increase the reliability of the electric drive 40, a second switching element, a resistor and a diode of the charging circuit connected by the anode of the diode to the positive voltage bus of the rectifier are additionally introduced. and a resistor to the terminal 45 contact of the second switching element, two capacitors - accumulating and timing, two resistors - timing and leakage, with one capacitor plate and one terminal of the leakage resistor 50 connected to the rectifier negative voltage bus, the second storage capacitor plate connected to the movable contact of the second a switching element, the opening contact 55 of which is connected through a timing resistor to the connection point of the second output of the leakage resistor, the second lining yazadayuschego capacitor and the control terminal of the thyristor dynamic braking, with the nominal values additionally introduced elements of relations: to the floor or Thelkow identified in the Veda of the following □ "- · C) ypr ^Rbp - (ΰΑΑΰΓ Cf. Τι Rbo Snack. T ₂ Rap Rzar. ~ .11. Dreams U ³ 0m. where and _In UPR “the amplitude value of the rectified voltage, In: ! ACL thyristor dynamic braking current, A; 5 R _Bp - resistance of the timing resistor: Svr - capacity of time-consuming condensing! Op <3 * Snack ~ storage capacitance condenser 10 sashra, Ф: oh, - is the resistance of the leakage resistor. Ohm; Fire ”resistance of the charging resistor. Ohm; 15 Τι, Т ₂ , Тз - time parameters at which the normal functioning of the device is ensured.