Product Introduction

Frame circuit breakers (also known as universal circuit breakers) are core control and protection devices used in the main circuits of low-voltage distribution systems. They are mainly applied in AC 380V/220V low-voltage networks, responsible for the "making/breaking of normal load current," "breaking of short-circuit fault current," and "overload/overvoltage/undervoltage protection" functions in key circuits such as low-voltage main incoming lines, busbar sections, and large-capacity motor feeders. They serve as the "first line of defense" ensuring the safety of main circuits in low-voltage distribution cabinets (such as GGD, GCK series).

Core Definition and Key Features

The core positioning of frame circuit breakers is "low-voltage high-capacity switch + comprehensive protection." Compared with miniature circuit breakers (MCB) and molded case circuit breakers (MCCB), they have the following significant features:

High capacity: Rated current usually ranges from 630A to 6300A (far exceeding the 1250A upper limit of molded case circuit breakers), with short-circuit breaking capacity reaching 50kA to 200kA, suitable for the high current demands of low-voltage main circuits;

Comprehensive protection: In addition to basic overload and short-circuit protection, it can be extended to overvoltage, undervoltage, phase loss, ground fault (leakage) protection functions, with protection parameters precisely set and adjusted;

Modular structure: Uses a "frame-type base + detachable modules" design (such as independently replaceable operating mechanisms, trip units, auxiliary contacts), offering high maintenance flexibility;

Multiple operation modes: Supports manual and electric switching, some intelligent models support remote communication control, suitable for unattended power distribution scenarios (such as data centers, industrial plants).

Working Principle

The working logic of frame circuit breakers revolves around two main scenarios: "normal operation control" and "fault protection," with the specific process as follows:

1. Normal operation: switching control

Closing: The operating mechanism's spring is charged manually or electrically. After charging, a "close command" is triggered, releasing the spring energy to drive the main contacts to close, connecting the conductive circuit and supplying power normally; simultaneously, the opening spring is charged in preparation for the next opening.

Opening: Upon receiving a "manual open button" or "remote control signal," the operating mechanism releases the opening spring energy, driving the main contacts to separate quickly. The arc generated at the moment of opening is divided and cooled by the arc extinguishing chamber and finally extinguished, cutting off the circuit.

2. Fault protection: automatic opening

Monitoring: The electronic trip unit collects the main circuit current in real-time through current transformers (built-in or external) and monitors voltage signals;
Judgment: The collected current/voltage is compared with preset protection parameters (such as overload current threshold, short-circuit current threshold). If the threshold is exceeded (e.g., short-circuit current reaches 10 to 20 times the rated current), it is determined as a fault;

Opening: The trip unit sends an electrical signal to drive the trip mechanism to operate, forcibly opening the operating mechanism, disconnecting the main contacts, cutting off the fault circuit to prevent equipment damage or fault expansion (such as avoiding large-scale power outages caused by busbar short circuits).

Application Scenarios

As the "main switch" of low-voltage main circuits, frame circuit breakers are mainly applied in the following scenarios:

Low-voltage main incoming cabinet: Installed at the low-voltage incoming end of buildings (such as shopping malls, office buildings) or factories, controlling the power access and disconnection of the entire low-voltage system;

Busbar section cabinet: Used for sectional control of low-voltage busbars. When a busbar section faults, the faulty section can be disconnected to ensure normal power supply to other busbars (improving power supply reliability);

Large-capacity load feeder cabinet: Controls power supply for high-power equipment (such as motors above 100kW, large air conditioning units), providing overload and short-circuit protection to prevent load faults from affecting the main circuit;

Data center / new energy scenarios: Intelligent frame circuit breakers are used for low-voltage side control of UPS systems and photovoltaic inverters, supporting remote monitoring and fault alarms, suitable for unattended operation requirements.