1. Operating Temperature: 

The working ambient temperature of the fuse should be within the specified operating temperature range. When the ambient temperature exceeds 25℃, it should be degraded according to the temperature reduction curve.

2. Rated Voltage: 

The highest voltage in the circuit where the fuse is located shall not exceed the rated voltage of the fuse.

3. Rated Current:

The working current passing through the fuse shall not exceed 75% of the rated current.

4. Short Circuit interception capacity: 

The maximum short circuit current that may occur in the circuit where the fuse is located should not exceed the short circuit interception capacity of the fuse.

5. Fuse characteristics: 

The fuse speed of the fuse when the overload current that needs to be cut off should meet the application requirements.

6. I2t: 

I2t of the fuse shall be greater than I2t of the surge current.

Fuse Selection Method

1) Determine the type of fuse according to the use conditions.

2) When selecting the specifications of the fuse, select the specifications of the melt first, and then select the specifications of the fuse according to the melt.

3) The protection characteristics of the fuse should cooperate well with the overload characteristics of the protected object.

4) In the distribution system, all levels of fuses should match each other, and generally the rated current of the upper stage melt is 2~3 times larger than the rated current of the next stage melt.

5) For the fuse to protect the motor, attention should be paid to the impact of the motor starting current, the fuse is generally only as the short circuit protection of the motor, overload protection should be a thermal relay.

6) The rated current of the fuse shall not be less than the rated current of the melt; the rated breaking capacity shall be greater than the maximum short-circuit current that may occur in the circuit.

Summary:

The type of fuse is mainly based on the protective characteristics of the load and the size of the short circuit current. For motors and lighting branches with small capacity, the fuse is often used as overload and short circuit protection, so the melting coefficient of the melt is appropriately smaller. The RQA series of fuses with lead-tin alloy melt are usually used. For large capacity motors and lighting trunk lines, short circuit protection and breaking capacity should be considered. The RM10 and RL1 series fuses with relatively high score breaking capability are usually used; when the short-circuit current is very high, the current-limiting RT0 and RTl2 series fuse should be used.

Fuse Precaution

1. The fuse shall be connected in series with the line, installed vertically and installed on each phase line; the fuse is not allowed on the neutral line of two-phase three-wire or three-wire and phase four-wire circuit.

2. The incoming power supply end of the screw insurance shall be connected to the center point of the base, and the power outlet line shall be connected to the threaded shell; the insurance is used for vibration places.

3. When the power load is greater than 60A, and the lighting or electric heat load (220V) is greater than 100A, the pipe insurer should be used.

4. The electric degree meter voltage circuit and electrical control circuit should be equipped with control insurers.

5. Porcelain insertion insurance uses qualified lead combined gold wire or copper wire, and multiple fuse shall not be used instead of a large fuse.

6. The fuse shall be intact and destructive, and the contact shall be close and reliable. Combined with the maintenance of the power distribution device, check the contact situation, discoloration, deformation and aging of the molten parts, and replace the molten parts if necessary.

7. After the fuse is selected, the selected fuse can protect the wire. If the wire section is too small, it should be increased appropriately increased.

8. The copper cap of the drop-type fuse should be held to more than 3 / 4 of the contact on the melt pipe, and the melt pipe or melt surface should be free of damage or crack.

9. All fuses shall not be arbitrarily thickened at will or replaced with copper and aluminum wire.

10. In the new workshop, apartment and building, each entry point device has multiple electrical meters. In addition to the total fuse box and fuse installed at the entrance, each electrical meter should be installed with a fuse.