Fire pump control cabinet generally has four startup modes: direct startup, star triangle, automatic depressurization and soft start. Their advantages and disadvantages are as follows:

1) start directly

Advantages: less gas components are needed, the starting mode is simple, the cost is low, and it is more suitable for low-power motors. It is necessary to know that the current directly started by the motor is more than 5 times that of normal operation. Theoretically, as long as the capacity of the power supply lines and transformers for the motor is more than 5 times that of the motor, the fire pump control cabinet can be directly started. For small-capacity motors, this is easy to realize, which is why most small-capacity motors are directly started in practical applications.

Disadvantages: large-capacity motors are not suitable. On the one hand, it is difficult for power supply lines and transformers to meet the conditions of direct starting of motors; On the other hand, strong starting current will impact the power grid and the motor, affecting the service life of the motor, which is not good for the power grid.

Dual power supply control equipment

2) star triangle begins

Advantages: By changing the wiring mode of the motor, the voltage is reduced, and the equipment is relatively simple and economical.

Disadvantages: more wiring and higher cost; At the same time, it has a certain impact on the power grid when it is started.

3) Automatic coupling step-down startup

Advantages: low requirements for the use environment, less failures; The voltage is reduced by the autotransformer and supplied to the motor, and the voltage can be adjusted freely.

Disadvantages: the step-down current is relatively large and the impact torque is large. There are secondary impact current and impact torque in the starting process, so it is impossible to start frequently, and the motor has poor protection.

Automatic detection control equipment for fire pump

4) soft start

Advantages: little influence on power grid voltage fluctuation, little impact on power grid, good motor protection and long motor life, and it is suitable for high-power and heavy-duty motors. During soft start, the starting current is generally 2-3 times of the rated current, and the voltage fluctuation of the power grid is generally within 10%, which has little influence on other equipment. The influence of large current directly started by super-large motor on the power grid is almost similar to that of three-phase short circuit, which will cause power oscillation and make the power grid unstable. The starting current contains a large number of higher harmonics, which will resonate with the circuit parameters of the power grid at high frequency, resulting in relay protection misoperation, automatic control failure and other faults. The current is greatly reduced during soft start, and the above influence can be completely eliminated.

Disadvantages: high investment cost, high requirements for use environment and low overload capacity of electronic components.

Fire pump control equipment