SU687551A1 - Device for the control of dc motor - Google Patents

Description

(54) DEVICE FOR CONTROLLING DC MOTOR MOTOR

one

The invention relates to the field of electrical engineering and can be applied in stabilized DC electric drives.

Devices for controlling a direct current electric motor are known, comprising a series-connected main power source, a stabilization unit, a current limiting device and an electric motor 1, 2.

During start-up, the motor current in a known device passes from the main power source through a series-connected current limiting device and a stabilization unit, therefore the start-up time cannot be short due to unavoidable energy losses in the series-connected current limiting device and the stabilization unit. The calculation of the stabilization unit has to be made based on the starting current of the engine, which, with a high frequency of this current relative to the nominal current of the engine, leads to a large overestimation of the installation mosh, the stability of the elements of the stabilization unit and the complexity of the circuit. All this causes power losses in the stabilization mode and reduces the efficiency and reliability of the device as a whole.

The aim of the invention is to increase the efficiency of the device.

This is achieved by the fact that an additional power source and a thyristor connected in series and according to and connected in parallel to the motor are introduced into the device for controlling the direct current motor, which contains the main power supply unit, the stabilization unit, the current limiting device, in series.

FIG. 1 shows a functional diagram of the device; in fig. 2 shows an embodiment with a specific circuit of an additional power source; in fig. 3 - graphics, showing the operation of the device.

Claims (2)

The device contains a series-connected main power source 1 (see Fig. 1), a stabilization unit 2, a current limiting device 3, an electric motor 4. A series-connected thyristor 5 and an additional power source 6 are connected in parallel with the electric motor. The additional power source can be made in the form of a capacitor 7 (see Fig. 2) connected via a resistor 8 to the main power source 1. The operation of the device occurs in the following way. The current limiter 3 limits the current at the output of the stabilization unit 2 at level ii (see Fig. 3). somewhat larger than the rated current of the engine 4 in the stabilization mode 1l, taking into account possible current oscillations in this mode. The thyristor 5 opens when a pulse corresponding to the "Start" command arrives at its control electrode, in this case the engine receives power mainly from an additional source 6 - current ij. A minor part of the motor current comes from the stabilization unit 2 through the current limiting device 3 (Fig. 3). Since the voltage drops on the internal resistance of the additional source 6, the voltage on the engine 4 increases smoothly, and the current of the engine 4 decreases as the speed of its rotation increases. At time ti, the motor current 4 decreases to a value that flows from stabilization unit 2 i, i.e., the current from auxiliary power supply 6 becomes zero, and the voltage on motor 4 reaches the voltage of auxiliary power supply 6. Since the current through the thyristor 5 becomes equal to zero, the thyristor closes and further acceleration of the motor 4 (ti -ti) is carried out from the stabilization unit, which provides sufficient current it to terminate the acceleration of the motor, since by the time the motor speed is close to nominal. At time t, the engine start mode 4 ends and the stabilization mode begins when the rated current of the engine ia enters the engine from the stabilization unit 2 and the voltage on the engine is equal to UCT. Thus, the energy for starting the engine 4 comes from an additional source 6, a stabilization unit 2 and a current limiting device 3, thereby starting time can be made arbitrarily small, depending on the power of the additional source b and the thyristor 5. In the start mode, the unit 2 stabilization gives a small current ii to motor 4, therefore the elements of stabilization unit 2 and device 3 for limiting current can only be calculated for stabilization mode. This allows us to simplify the circuit, apply elements with a small installation capacity, which leads to a decrease in power losses in the stabilization mode and to an increase in the efficiency and reliability of the device. In order to simplify, an additional source b can be made on the capacitor 7 and the resistor 8 (see Fig. 2). The capacitor 7 transfers the energy accumulated from the main source through the resistor 8 to the start of the motor 4, the voltage across the capacitor changes in accordance with the graph in FIG. 3. The thyristor 5 is disconnected at equal voltages on the motor 4 and the capacitor 7. Claim of the invention A device for controlling a direct current electric motor comprising a series-connected main power source, a stabilization unit, a current limiting device, characterized in that devices, an additional power source and a thyristor are connected to it, connected in series and in accordance with and connected in parallel to the motor. Sources of information taken into account during the examination 1.Leonenko L.I. and Ovsnikov O.S., On permissible limitations of the output current of amplifiers in electric drives. In-se .: “Electronic equipment in automation. Issue 7, 1975, p. 89-93. 2. USSR author's certificate number 514408, cl. H 02 R 1/04, 1976. 2