Choosing of circuit breakers, selection of air switches
Circuit breakers, the full name of automatic air circuit breakers, also known as air switches, are commonly used low-voltage protection appliances. Realize functions such as short circuit and overload.
The circuit breaker is used as the main power protection switch or the branch line protection switch in the household power supply. When a short circuit or overload occurs in residential lines or household appliances, it can automatically trip and cut off the power supply, thereby effectively protecting these devices from damage or preventing accidents from expanding.
Families generally use two-pole (ie 2P) circuit breakers for general power protection and single-pole (1P) for branch protection.
If the rated current of the circuit breaker is selected too small, the circuit breaker will trip frequently and cause unnecessary power failure. If the rated current of the circuit breaker is selected too large, the expected protection effect will not be achieved. It is very important to select the rated capacity current correctly.
The specifications of general small circuit breakers are mainly divided into 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A, 80A, 100A, etc.; total value?
1. First calculate the value of each branch current
①Pure resistive loads, such as light bulbs, electric heaters, etc., directly divide the indicated power by the voltage That is,
Formula I=power/220v;
For example, 20w bulb, branch current I=20W/220=0.09A
Electric fan, electric Irons, electric blankets, water heaters&from=forum9″ target=”_blank” class=”ReplaceKeyword”>electric water heaters, electric heaters, rice cookers, electric frying pans, vacuum cleaners, air conditioners, etc. are resistive loads.
How to choose a circuit breaker is a professional technical problem. Briefly, you can choose from the following 6 points: 1. First, select according to the rated voltage, and the rated voltage should be consistent. 2. The rated current of the circuit breaker should be greater than It is equal to the rated current of the circuit used. 3. The rated breaking current of the circuit breaker should be greater than or equal to the short-circuit current of the circuit used. 4. According to the environmental conditions, such as altitude, temperature and humidity, select the circuit breaker that meets the requirements. 5. According to the brand Choose a circuit breaker with high quality and cost-effectiveness. 6. For special breaking conditions, check the circuit breaker. However, different types of circuit breakers should be used for different loads.
The choice of air switch Principles
1. Determine the type and protection form of the circuit breaker according to the protection requirements of the line – determine the choice of frame type, device type or current limiting type, etc.
2. The rated voltage UN of the circuit breaker should be equal to or greater than the rated voltage of the protected circuit.
3. The rated voltage of the undervoltage release of the circuit breaker should be equal to the rated voltage of the protected circuit.
4. The rated current of the circuit breaker and the rated current of the overcurrent release should be greater than or equal to the calculated current of the protected circuit.
5. The ultimate breaking capacity of the circuit breaker should be greater than the maximum breaking capacity of the circuit The effective value of the short-circuit current.
6. The protection characteristics of the upper and lower circuit breakers in the distribution line should be coordinated, and the protection characteristics of the lower level should be located below the protection characteristics of the upper level and do not intersect.
7. The long-time-delay tripping current of the circuit breaker should be less than the continuous current allowed by the conductor.
