SU922979A1 - Rotational speed regulator for dc electric motor - Google Patents

Description

The invention relates to electrical engineering, in particular, to a DC electric drive, and can be used in systems for regulating the frequency of rotation of DC motors.

A device for adjusting the rotational speed for a direct current electric motor, comprising a resistive voltage divider and a thyristor connected to the power source, is connected in series with the motor armature [1].

The closest to the proposed technical essence is in ustroyst- ^15, comprising a power supply connected to a resistive voltage divider and a thyristor connected in series with the motor armature, shunted by a diode, the thyristor is shunted by a chain of serially connected variable resistor, diode and second capacitor upravlya2

key, the output of which is connected to the control electrode of the thyristor [2},

A disadvantage of the known devices is the emergence of the mode "slip half-periods of voltage" when operating in the range of cut-off angles from 120 to 175 °, which leads to the limitation of the frequency control range of rotation.

The purpose of the invention is the extension of the range of speed control.

This goal is achieved by the fact that the device additionally introduced a discharge diode, and a controlled key made in the form of a comparator, the inverting input of which is connected to the midpoint of a resistive divider, non-inverting input - to the connection point of the second diode and capacitor and to the anode of the discharge diode, the cathode of which is connected with thyristor anode.

FIG. 1 is a circuit diagram of the device; on

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922979 4

FIG. 2 - stress diagrams on epemen-. At point b, a thyristor 4 will open with a smaller controller. The winding 2 of the excitation, the armature of the electric motor 3 through successively connected 5 thyristor 4, the resistive dividers 5 and 6 of the voltage, are connected by a delayed neck, transmitting a large power supply to the power source 1. The comparator 7, the output of which is connected to the control electrode of the thyristor 4, the inverting input of the comparator 7 is connected to the middle 10 point of dividers 5 and 6, the non-inverting input is connected to the connection point of a series-connected capacitor 8 and a diode 9, which together with the series-connected variable resistor 15 10 form a chain that shunts a thyristor 4. A diode 11 shunts a chain of diodes 9 and a resistor 10 connected in series, and a diode 12 shunts the armature of an electric motor 3. 20

The device works as follows.

In the input circuit of the comparator 7, the pulsating voltage 11d is removed from the resistor 5, with the voltage removed from the capacitor 8 and determined by the parameters of the resistor 10 and diode 9, as well as the counter-EMF arising at the armature winding 3. When voltage 1 ) 5, coming to the inverting input of the comparator 7, will become equal to the voltage Ma, coming to the non-inverting input device 7 will work and a voltage pulse will appear at its output and LYH. KOMSHR., ₃₅ entering the thyristor control circuit 4. This impulse is formed from the source voltage ί! Pete. and its energy does not depend on the cut-off angle.

The thyristor 4 opens and supplies voltage 40 b to the armature winding of the electric motor 3. After opening the thyristor 4, the capacitor 8 will begin to discharge along the circuit: diode 11, thyristor 4. The voltage and ₃ will begin to decrease exponentially and 45 the comparison with 5 will occur at point a ^, after What Comparator 7 will turn off. Thus, the duration of the starting pulse will be determined by the time between a - a1 (Fig. 2). ₅₀

With increasing load on the motor shaft, its rotational speed and back-EMF are reduced and the capacitor 8 is charged to a larger value. In this case, the voltage comparison will occur earlier

ness into the armature winding of the electric motor 3 and thereby compensating for the increased load.

When reducing the load on the motor shaft, its rotational speed and back-EMF will increase, and the capacitor 8 will be charged to a lower value. Comparison of the voltage will occur later - at point 6 and the thyristor 4 will open with a greater delay, reducing the power transmitted to the armature winding of the electric motor 3, compensating for the increase in the frequency of rotation of the electric motor.

By changing the value of the resistor 10, you can smoothly change the frequency of rotation of the electric motor within wide limits.

Thus, the proposed device allows you to work with large cut-off angles, which expands the range of regulation of the frequency of rotation of the motor.

Claims (1)

Claim A speed regulator for a DC motor containing a resistive voltage divider connected to a power source and a thyristor connected in series with the armature of a motor shunted by a diode, the thyristor being shunted by a chain of series-connected variable resistor, second diode and capacitor, controlled key whose output is connected to to the control electrode of the thyristor, which is characterized by the fact that, with an extension circuit of the frequency control range, it additionally about introduced freewheeling diode and controllable switch is formed as a comparator, the inverting input of which is connected to the middle point of the resistive divider, neinvertiruyushy input to the junction point of the second diode and the capacitor and to the anode of the discharge diode, the cathode of which is connected to the anode of the thyristor.