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The advantages and disadvantages of the direct start of the fire inspection cabinet

Jan 11, 2021


The advantages and disadvantages of the direct start of the fire inspection cabinet:


Advantages: less requirements for fire inspection cabinets, simple starting method, low cost, and more suitable for low output power motors. The immediate starting current of the motor is more than 5 times that of normal operation. In theory, if the motor's power supply system route and transformer capacity are more than 5-7 times the motor volume, it can be started immediately. For small-volume motors, this type of regulation is very easy to complete, so most small-volume motors are started immediately without starting.



Fire xun'jian'gui

Defects: For large-space motors, on the one hand, the route and transformer capacity cannot consider the motor's immediate starting standard. On the other hand, the strong starting current affects the power grid and the motor, affecting the motor's service life, and is not good for the power grid.


Advantages and disadvantages of soft start of fire inspection cabinet:


Advantages: The impact on the working voltage fluctuation of the power grid is small, and the impact on the power grid is small. The actual maintenance effect of the motor is good, the service life of the motor is longer, and it is more suitable for high-power and super-heavy motors.


1. When the motor is started immediately under the complete working voltage, the starting current will be 4-7 times of the rated voltage. When the volume of the motor is large, the amount of starting current will cause a sudden drop in the working voltage of the power grid, which will affect the normal operation of other machinery and equipment on the power grid. During soft start, the starting current is generally 2-3 times of the rated voltage, and the fluctuation of the grid working voltage is generally less than 10%, which has little effect on other machinery and equipment.


2. The impact of the large current that large and medium-sized motors start immediately on the power grid is basically similar to the impact of a three-phase short-circuit fault on the power grid. This usually causes the power grid to oscillate, and the reliability of the power grid is lost. The first-order harmonic currents will cause high-frequency co-shock with the main parameters of the power supply circuit of the power grid, resulting in relay protection devices.


Maintenance of common failures, common failures of automatic control systems, etc. During soft start, the starting current is greatly reduced, and the influence can be completely eliminated.


3. The Joule heat caused by the large current continuously works on the outer insulating layer, accelerating the embrittlement of the insulating layer and reducing the service life of the insulating layer. The mechanical equipment force caused by the large current causes the electrical conductors to rub against each other, reducing the service life of the insulation layer, and the DC voltage of the motor can be adjusted from zero during soft starting to avoid overvoltage damage.


4. In the motor stator electromagnetic coil and rotor squirrel cage rod, the larger current is reduced by about half, the instantaneous heat generation is only about 1:4 of the immediate start, the service life of the insulation layer is greatly increased, and the large impact caused by soft magnetism The force will cause the clamping loosening of the electromagnetic coil and the rupture of the wound motor bar. When starting the soft start, the impact force is greatly reduced due to the large current and the small amount.


Defects: high project investment, high environmental protection regulations, and low load working capacity of the original electronic components


Check the advantages and disadvantages of automatic coupling jump start


Advantages: The applied natural environment regulations are not high, and there are few common faults. After the transformer reduces the working voltage, the motor can adjust the working voltage at will.


Defects: The blood pressure lowering current is large, the impact torque is large, and the secondary impact current and the impact torque exist during the whole starting process. It cannot be started frequently, and the actual effect of motor maintenance is poor.


The pros and cons of the star triangle start of the detection cabinet


Advantages: Delta start is to change the interface mode of the motor, the complete working voltage is reduced, and the relative simplicity of the machine and equipment is more standard.


Defects: The more the three-way start-up wiring, the greater the project investment, and the start-up of the fire inspection cabinet will also have a certain impact on the power grid.