Smooth soft starting device of direct current motor

Abstract

The invention discloses a smooth soft starting device of a direct current motor. The smooth soft starting device comprises a main loop based on an insulated gate bipolar transistor (IGBT) and a control device based on a singlechip and a liquid crystal display, wherein a Hall current voltage detection unit samples an armature current, an armature voltage and an exciting current of the direct current motor in real time and sends detected operating parameters into a central processing unit; the central processing unit transmits the operating parameters to a display record unit for displaying; and a temperature detection unit obtains a temperature value of an IGBT module and sends the temperature value into the central processing unit. An IGBT driving unit outputs pulse width modulation (PWM) control quantity to drive the IGBT module, so the size of an armature winding current of the direct current motor is controlled, and the contactless and stepless rising current starting of the direct motor is realized. The smooth soft starting device of the direct current motor has the advantages that: the defects of the conventional direct current motor control system can be completely overcome; the smooth stepless starting of the direct current motor can be realized; and starting and operating currents are always below a rated current of the motor without any impact on a direct current system and the direct current motor.

Description

Technical field [0001] The invention relates to the technical field of power electronic control, and more specifically, to a smooth soft start device for a DC motor. Background technique [0002] The most notable feature of a DC motor when it is started is the large starting current, and the maximum impact current can even reach 15-20 times the rated current, which will cause the DC system to be subjected to a huge current impact, which will cause the motor to be mechanically impacted and damage the motor. [0003] In order to avoid the huge current impact when the DC motor is started, the most widely used starting method in thermal power plants is armature circuit series resistance starting. When this starting method is started, a starting resistance is inserted in the DC motor armature circuit. When the motor starts The starting current of the motor is limited by the resistance step-down. The starting resistor is a variable resistor connected in series with three resistors. Duri...

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Problems solved by technology

[0004] 1. It cannot completely solve the problem of large inrush current during the starting process of the DC motor. During the starting process, the starting current of the DC motor is still several times greater than its rated current, and it is still possible that the motor will be accelerated and damaged due to excessive starting current;

[0005] 2. The control principle is outdated, the method is complicated, there are too many links, the failure rate is extremely high, and the maintenance workload is heavy

This starting method needs to be composed of several large-capacity DC contactors, intermediate relays, and time relays. Due to the large number of components, the failure rate is extremely high, the cabinet is very crowded, and maintenance is extremely inconvenient;

[0006] 3. During the start-up process, if any level of resistance is not switched, the DC motor will not operate normally, the resistance will heat up seriously, and the motor will be overloaded;

[0007] 4. During the start-up process, the start-up current is still relatively large, causing the battery to be impacted by the current, and the output voltage is reduced. If any primary resistance is not switched, the operating condition of the battery will be deteriorated, posing a threat to the normal operation of the electrical secondary circuit. , For example, the relevant switch refuses to jump in case of an accident, causing the accident to expand;

[0008] 5. During the process of stopping the pump, the counter electromotive force of the DC motor is instantly added to the DC system through the arc light when the DC contactor is disconnected, resulting in large fluctuations in the voltage of the DC system. The work poses a great threat, such as the phenomenon that the switch in the field is running for no reason, which is caused by it;

[0009] 6. In order to cope with the ultra-high current when the DC motor starts, the DC power supply system has to increase the capacity, which increases the equipment investment

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