A miniature circuit breaker is an electromagnetic device with integrally molded insulation material. The main function of the device is to switch the circuit. It means that when the circuit is connected when the current flowing through the circuit exceeds the set value or limit, the miniature circuit breaker will automatically disconnect the circuit. Miniature circuit breakers are designed to protect cables downstream of equipment and prevent overload and short-circuit damage to cables and equipment. When necessary, the device can be manually turned on or off at any time like an ordinary switch.
Type of miniature circuit breaker
There are 3 types of miniature circuit breakers, type B, type C, and type D. The tripping speed depends on the degree of overload, which is usually determined by the thermal device in the miniature circuit breaker. The following is a typical circuit breaker trip curve, showing the current value and duration required to trigger a circuit breaker protection.
These curves vary by manufacturer and model. According to the most commonly used datasheet of the ABB S201M series, generally speaking, the working range of B type circuit breaker curve is 3 to 5 In, C type is 5 to 10 In, and D type is 10-14 In.
The working principle and working conditions of miniature circuit breakers
The working principle of the miniature circuit breaker is to trip when the circuit is overloaded or the system is short-circuited. Its rated current is 6A or 10A, depending on its intended use, such as residential, commercial, industrial or public buildings. The miniature circuit breaker trips under two conditions, namely steady-state current and instantaneous current. Instantaneous current is also call surge current.
What is inrush current?
Inrush current refers to the input current that enters the LED lamp in a very short period of time. During the power-up phase, the LED power supply in the lamp can be regarded as a capacitive device. The figure below shows the variation of a typical surge current in a 230Vac 50Hz AC line input with a capacitive load.
If multiple LED lamps are connected at the same time, the maximum surge current and its duration may trigger the miniature circuit breaker.
Calculation formula:
The formula for calculating the number of LED drive power sources that a miniature circuit breaker can drive is: Min (Itrip/Idriver, Ihold/Iinrush). The value is the minimum value between the two values.
Itrip: N × rated current of the miniature circuit breaker (N depends on different types of miniature circuit breakers).
Idriver: The maximum average input current of the LED driver.
Ihold: The instantaneous rated current of the miniature circuit breaker.
Iinrush: The maximum inrush current of the LED driver.
To sum up:
1. Users need to be very careful when choosing miniature circuit breakers in order to use them correctly.
2. When the miniature circuit breaker trips, either a steady-state current overload or an instantaneous current overload.
3. Consult relevant sales personnel when choosing miniature circuit breakers. Ute Power also provides low inrush current drive products, which will enable at least 5 times more power sources to be connected under the same miniature circuit breaker.
