Jan 12, 2021
Application of microcomputer soft starter in controlling fire pump and spray pump
Abstract: The microcomputer-controlled motor soft starter solves the discussion of the problems related to the power frequency (star angle and auto-coupling step-down) start involving fire water supply technology.
Keywords: soft starter, electrical shock, mechanical shock, PLC programmable, mechatronics, power factor
With the rapid development of modern fire protection in our country, the application of microcomputer soft start technology in the fire water supply system is crucial. It can completely solve many problems of fire pump power frequency (star angle or auto-decompression) start.
1. Existing problems in the control and start mode of the water pump of the fire water supply system.
1. In the fire-fighting water supply system, whether the fire-fighting pump and sprinkler pump can ensure normal operation at any time is of crucial importance. In the electric control system, the fire pumps and spray pumps established in the past have serious technical problems in starting with power frequency (star angle or auto-coupling step-down starting method). This control method has poor reliability and instability, and will cause electrical shocks and mechanical shocks every time it starts and stops. As a result, a series of technical problems have occurred: For example, the high starting current of the larger water pump motor under load may easily cause the control system to crash, trip, or power failure. At the same time, water hammer is caused to the water system pipe network, and it is easy to cause damage to valves, check valves, and water pump couplings, which seriously affect the service life of the equipment. An immeasurable hidden danger has been buried in the fire protection project, which is unsafe and unreliable.
In order to solve this problem, a special person had to be on duty to look after the valve. The valve was regularly opened and the pump was energized to prevent the pump from rusting due to long-term idleness. If there is a fire, professional personnel must also work in accordance with the pre-established operating procedures: first close the valve, then turn on the power to start the motor, and then slowly open the valve when it runs normally. (At this time, the valve is working because the pump is running. If the pressure is too high, the valve can be opened with greater force, and it is easy to damage). It will take at least 10 minutes or even more than half an hour from the information of the fire occurrence to the normal operation of the equipment. Difficulty in starting, resulting in delays, loss of the most advantageous time to extinguish the fire, and the resultant fire from a small fire to a large fire, which is unimaginable.
2. The application of star angle or auto-coupling step-down starting method is allowed to be adopted in the fire protection design code and conforms to the design code. However, in combination with my country's national conditions, in practical applications, technical problems exist, coupled with unclear management responsibilities, resulting in the use of fire-fighting facilities. Can not ensure the safe and normal operation of fire fighting equipment. Especially in enterprises and institutions with full power consumption, such problems are more likely to be exposed.
Often, some fire-fighting facilities generally pass the acceptance and reach the qualification when the newly-built project is checked and accepted. However, when it is put into normal operation, the fire pump and spray pump cannot start normally. This is because the transformer is working at full load according to the design. If the large motor suddenly starts at this moment, the current is too high and it is easy to cause a crash Or the occurrence of problems such as power failure. If it continues, it will lose the ability to manually start and automatically start the fire extinguishing, which will inevitably lead to serious consequences.
In summary, the power frequency (star angle and auto-coupling step-down) startup mode has the following main problems:
(1) Large electrical impact force; (2) Large mechanical impact force; (3) Larger water pump motors need manual auxiliary start, so it is difficult to realize automatic inspection; (4) Larger motors start with load and it is difficult to close the valve Automatic and manual start-up makes the start-up time too long and delays the time to put out the fire.
2. The characteristics and performance of using a microcomputer soft starter to control the fire pump
Using a soft starter, large fire water pumps do not need to close the valve to start, and can be started directly. In the fire protection system, it completely solves the problems of crashes or power failures caused by the heavy load of the pump motor and the high starting current. This technology mainly lies in the microcomputer controlling the voltage conduction angle, so that the starting current and voltage have slope voltage and current limitation under the digital control of the microcomputer. The ramp voltage and current can be set with a variety of starting methods, so that the motor input voltage and current are within the design rating range, reducing and reducing the impact current, step by step (gradual increase or decrease working mode), to achieve a smooth soft start and soft stop effect . This technology can achieve mechatronics, automation, unmanned operation, safe and reliable. This product has passed the type inspection of the National Fixed Fire Extinguishing System and the Quality Supervision and Inspection Center of Fire-resistant Components, and the qualified product is determined. The computer automatically controls the fire water supply equipment, and the PLC programmable controller is the main control unit. The formation of control contactless, automatic inspection according to the set period; automatic control of the electric valve to ensure flexible opening and closing of the return pipe; automatic recording of the operating time and operating status; sound and light alarms when the fire signal is encountered; sound and light when the equipment fails Alarm; It has various functions such as remote control, manual and automatic timing switching, and supplementary operation.
SSR motor soft starter, with phase sequence, phase failure, overcurrent, overvoltage, undervoltage, and overheat protection functions. When the protection function is working, the motor power is automatically cut off to protect the motor from burning out, and sound and light alarms are issued at the same time. DWQ series motor soft starter has no contact, no spark, no noise, no vibration, long life, high reliability, and small maintenance workload.
SSR series motor soft starters change the original start control mode, and solve the key problems for automatic safe and reliable control. No need to worry about the difficulty of starting a larger motor with load. At the same time, the impact force caused by the change of current is avoided, the mechanical system itself is easily damaged, and the service life of the mechanical system, electrical control system and motor is prolonged.
SSR series motor soft starters, through microcomputer control, improve the power factor of the motor, and realize energy-saving and efficient operation.