Electrical Encyclopedia: The choice of low-voltage electrical appliances

The choice of electrical appliances

1) The electrical appliances selected for low voltage distribution design should meet the following requirements:

1. The rated voltage of the appliance should be compatible with the nominal voltage of the loop;

2. The rated current of the appliance should not be less than the calculated current of the loop;

3, the rated frequency of the appliance should be compatible with the frequency of the loop;

4, electrical appliances should adapt to the environmental conditions of the place;

5, electrical appliances should meet the requirements of dynamic stability and thermal stability under short-circuit conditions. The electrical equipment used to disconnect the short-circuit current shall meet the breaking capacity under short-circuit conditions.

2) Check the electrical appliance's breaking capacity under short-circuit conditions, and use the effective value of the expected short-circuit current cycle component at the installation site. When the sum of the rated motor currents near the short-circuit point exceeds 1% of the short-circuit current, it shall be included in the motor feedback. The effect of current.

3) Installation of isolated appliances

1. When maintaining, testing, and overhauling the equipment, it is necessary to set isolation appliances.

2. Isolated electrical equipment should be isolated from the live part of the circuit. When the faulty operation of the isolated electrical equipment can cause serious accidents, measures should be taken to prevent misoperation.

3. The isolation device should use switches that simultaneously disconnect all poles of the power supply or single pole switches that are close to each other.

4. The following appliances can be used for isolation appliances: single-pole or multi-pole isolation switches, isolated plugs; plugs and sockets; connecting pieces; special terminals that do not require removal of wires; fuses. Semiconductor appliances are strictly prohibited for isolation appliances.

4) The following electrical appliances can be used for the operation of the switch-off current:

1. Load switch and circuit breaker;

2, relays, contactors;

3, semiconductor appliances;

4, 10A and below plugs and sockets.