BLOG
Soft Start and Optimization Technology of AC Asynchronous Motor
Release time:
2024-07-05
Direct starting is a relatively simple starting method. When starting, the motor is directly connected to the power grid through a knife or contactor. The advantage of direct starting is that the starting equipment is simple and the starting speed is fast, but the direct starting is very harmful:
九洲封头
1. Hazards of direct starting
Direct starting is a relatively simple starting method. When starting, the motor is directly connected to the power grid through a knife or contactor. The advantage of direct starting is that the starting equipment is simple and the starting speed is fast, but the direct starting is very harmful:
(1) power grid impact: excessive starting current (no-load starting current can reach 4~7 times of the rated current, with load starting up to 8~10 times or more), will cause the grid voltage drop, affect the normal operation of other electrical equipment, but also may make the undervoltage protection action, resulting in harmful tripping equipment. At the same time, the excessive starting current will make the motor winding heat, thus accelerating the insulation aging and affecting the life of the motor;
(2) Mechanical impact: Excessive impact torque often causes the motor rotor cage bar, end ring fracture and stator end winding insulation wear, resulting in breakdown burning, shaft distortion, coupling, transmission gear damage and belt tear, etc;
(3) Impact on production machinery: The sudden change of pressure in the starting process often causes damage to the pipes and valves of the pump system and shortens the service life; it affects the transmission accuracy and even affects the normal process control.
All of these pose a threat to the safe and reliable operation of the equipment, and also cause excessive starting energy loss, especially when starting and stopping frequently. Therefore, there are the following restrictions on the direct start of the motor:
(1) Whether the production machinery allows the drag motor to start directly, which is a prerequisite;
(2) The capacity of the motor should not be greater than 10% to 15% of the capacity of the power supply transformer;
(3) The voltage drop △U during starting shall not be greater than 15% of the rated voltage. For medium and high-power motors, direct starting is generally not allowed, and certain starting equipment is required to complete the normal starting work.
2. New type of electronic soft starter
With the development of power electronic technology and microcomputer control technology, a series of electronic starting control equipment have been developed at home and abroad for the starting control of asynchronous motor to replace the traditional step-down starting equipment. The main circuit of the new type of electronic soft starter generally uses thyristor voltage regulating circuit, which is composed of six thyristors in two reverse parallel, connected in series to the three-phase power supply line of the motor. When the microcomputer control system of the starter receives the starting instruction, it carries out the relevant calculation and outputs the trigger signal of the thyristor. By controlling the conduction angle α of the thyristor, the starter can adjust the output voltage according to the designed mode to control the starting process of the motor. When the starting process is completed, the general starter will be the bypass contactor, short-circuit all the thyristor main circuit, so that the motor directly into the grid operation, in order to avoid unnecessary power loss.
Related News
Address: North of Qianyi Road, Laobagang, Hai’an, Nantong City
Technical Support: +86-15988298685
Sales Phone: +86-13813729006
After-sales service: +86-18862773030
Copyright © 2024 Nantong Senmat Electrical Machinery Co., Ltd. Business License