SU1399872A1 - D.c. electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in electric drives of pumps, fans, compressors. The aim of the invention is to simplify the device and reduce the ripple current. In the device, the current sensor 12 is made in the form of a serial excitation winding 15 connected between the second contact 10 and the common output of the converter 5. In this device, the level of the current limiting depends on the thermal state of the electric motor due to the use of the excitation winding 15 of the device. 1 il. SL

Description

: iW

The invention relates to electrical engineering and can be used in various devices (pumps, fans, compressors, electric power transducers, etc.), where the drive motor must ensure the stability of the output shaft rotational frequency during load variations or fluctuations of similar DC power supply

The aim of the invention is to simplify the device, increase reliability and reduce current ripple.

The drawing shows a diagram of a direct current electric drive.

The DC motor comprises an electric motor, the first winding terminal of the core 1 of which is through serially connected diodes 2 and 3 and the secondary half windings of the transformer 4 of the converter 5, the starting resistor 6, shunted by the contact of the accelerator contactor 7, and the first contact 8 of the linear contactor is connected to the positive terminal power supply 9, the negative terminal of which is connected to the second contact 10 of the line contactor.

The first output of the parallel winding

11, connected to the second winding terminal of the core 1 and the common terminal of the converter 5. The inputs of the converter 5 are connected to the accelerator contactor 7, the current sensor 12 and the sensor 13 of the motor rotation frequency. The device contains a capacitor 14 connected between the second winding terminal of the core 1 and the first connected to the second pin of the parallel excitation winding 11.

Current sensor 12 is made in the form of a series winding 15 connected between the second contact 10 of the line contactor and the common terminal of converter 5 and connected to the input of converter 5 through an RC low-pass filter made on resistors 16 and 17 and capacitor 18.

The RC filter time constant corresponds to the value of the time constant of the excitation winding 15. In this case, the output voltage of the sensor

12 current is proportional to the voltage drop created by the flowing current on the active resistance of the winding 15.

The device WG becomes the following 1M image.

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In the initial start-up interval, the voltage of the power source 9 through the starting resistor 6 and the output circuit of the converter 5 is supplied to the motor circuit. In this case, the converter 5 is turned off by a signal from the accelerator contactor 7.

The magnitude of the first inrush current in the core circuit is limited by the resistance of the starting resistor 6, the initial excitation is created mainly by the winding 15, but as the motor accelerates, the voltage and current in the circuit of the parallel excitation winding 11 increase. Then, at the second start-up stage, from the moment of contacting the contact of the accelerator contactor 7, which shunts the starting resistor 6, the full voltage of the source 9 is applied to the motor circuit. This ensures the second inrush current and the overclocking of the motor.

Then, from the moment the converter 5 starts operating, started, for example, with a time delay after the contact 7 is closed, the third final start-up phase begins. At the same time, taking into account the effect on the control inputs of the converter 5 of the output signals of the sensor 12 of the total current of the device and the sensor 13 of the engine rotation frequency, the inverter 5 provides a further increase in the voltage on the circuit, core 1 and parallel excitation winding 11 to form a near-optimal, i.e. . almost rectangular in form, current diagram of the current of the electric motor.

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In a static steady state operation of the electric drive, the load on the motor shaft, the voltage fluctuations of the power supply source 9 and other disturbing factors are compensated with the required degree of accuracy by appropriately adjusting the output voltage of the converter, at which the rotation frequency of the motor is stabilized at a predetermined nominal level. In this case, in the event of a current overload of the motor or converter 5, a current limitation is automatically provided at a given safe level due to the effect of the sensor 12 of the total current of the device on the control input of the converter 5. At the same time

the current limiting level is floating (i.e. it depends on the thermal state of the electric motor determined by the previous mode of its load) due to the use of a series excitation winding 15 as a current sensor.

Claims (1)

Thus, the device simplifies and increases reliability by eliminating the isolation diodes and using a series excitation winding as a sensor for the total current of the device, as well as reducing current pulsations by introducing a capacitor and using a series excitation winding as a common input throttle of the device. Invention Formula A DC motor that contains an electric motor, the first terminal of the winding of the core of which is through serially connected diodes and 99872 and the first contact of the linear contactor is connected to the positive terminal of the power supply, the negative terminal of which is connected to the second contact of the linear contactor. The first phase of the parallel field winding is connected to the second winding terminal of the core and the common terminal of the converter, the inputs of which are connected to the acceleration contactor, current sensor and motor rotation speed sensor, characterized in that, in order to simplify, improve reliability and reduce current ripple, a capacitor is inserted in it, and the current sensor is connected in the form of a series excitation winding connected between the second contact of the line contactor and the common output of the converter and connected to the converter input through KS-low pass filter, and a capacitor is connected between the second terminal of the winding core and trans the secondary half windings of the transformer, 25 um, connected at the same time with the second converter, start-up resistor, shunted by a contact of a contactor by picking up a parallel excitation winding.