LRM2-63 3P Miniature Circuit Breaker (3-pole MCB)

Main Features & Advantages

Basic Functions

1 Short-Circuit Protection

When a short circuit occurs in the three-phase circuit (including phase-to-phase short circuit and phase-to-ground short circuit), the internal electromagnetic release acts instantaneously, cutting off all three phase wires within 0.1 seconds. This prevents electric arcs, equipment burnout and fire hazards caused by short-circuit current.

2 Overload Protection

When the three-phase circuit operates under long-term overload (the current exceeds the rated current of the breaker), the internal bimetallic strip deforms due to heat, triggering delayed tripping to cut off the power supply. It effectively prevents wire overheating, insulation aging and circuit damage caused by long-term overcurrent.

3 Synchronous On/Off of Three Poles

The core advantage of 3P MCB is that it controls three phase wires (L1, L2, L3) synchronously. Whether it is manual switching or fault tripping, all three poles are turned on or off at the same time, ensuring that the three-phase circuit is completely de-energized after tripping, which greatly reduces the risk of electric shock during maintenance.

4 Manual Switching Control

It can be used as a manual isolating switch. Pushing the operating handle upward to the "ON" position turns on the three-phase power; pulling it downward to the "OFF" position cuts off the power, which is convenient for safe power interruption during circuit maintenance and equipment replacement.

5 Optional Auxiliary Functions

Some models can be equipped with auxiliary contacts, alarm contacts, shunt trips or leakage protection modules, which can realize remote control, fault status feedback and leakage protection, adapting to more complex three-phase power distribution scenarios.

Full Technical Specifications

Product Uses

How to Use 3P Miniature Circuit Breaker

1. Scope of Application

3P Miniature Circuit Breaker is suitable for three-phase power distribution systems with AC 50/60Hz and rated voltage of 380V/400V, mainly used for:

- Circuit protection and control of three-phase power equipment such as industrial production lines, three-phase motors and water pumps

- High-power three-phase load circuits such as three-phase distribution cabinets and air conditioning units in commercial places

- Main incoming switches or three-phase branch switches for three-phase power supply in large residences and villas

- Power distribution scenarios requiring high three-phase power supply balance and protection reliability

2. Pre-installation Notes

2.1. Installation and wiring must be carried out under complete power-off condition. Live working is strictly prohibited to avoid three-phase short circuit or electric shock accidents.

2.2. Confirm that the circuit breaker parameters match the circuit: rated voltage 380V/400V, rated current compatible with the total current of three-phase load (1A~63A), and breaking capacity (usually 6kA/10kA) meets the circuit requirements.

2.3. Install on a 35mm standard DIN rail and fix it in the distribution box to ensure firm installation and avoid vibration during operation.

2.4. Before installation, check the appearance of the circuit breaker to confirm that there is no damage, the handle is flexible, and there is no foreign matter blocking inside.

3. Correct Wiring Method (Key Point)

The 3P circuit breaker synchronously controls three phase wires (L1, L2, L3) and does not connect to the neutral wire (N) or protective earth wire (PE). The wiring rules are as follows:

- Upper terminals: Connect incoming phase wires L1, L2, L3 in sequence (the wiring order must correspond to the phase wires of downstream equipment to avoid reverse connection of three phases)

- Lower terminals: Connect outgoing phase wires L1, L2, L3 in sequence to the downstream three-phase equipment or circuit

- Neutral wire (N): Directly connect to the neutral busbar in the distribution box without passing through the 3P circuit breaker

- Protective earth wire (PE): Connect separately to the earth busbar in the distribution box, and it is strictly prohibited to connect to any terminal of the circuit breaker

⚠️ Note: The wiring must be firm to avoid terminal overheating caused by looseness; wrong connection or missing connection of phase wires is strictly prohibited, otherwise it will cause equipment failure or safety hazards.

4. Operation Instructions

4.1 Switching On for Power Supply

Push the operating handle upward to the "ON" position, all three phase wires are turned on simultaneously, the three-phase circuit supplies power normally, and ensure the three-phase current balance of downstream equipment.

4.2 Switching Off for Power Cut

Pull the operating handle downward to the "OFF" position, all three phase wires are disconnected synchronously, the entire three-phase circuit is completely de-energized, and maintenance and equipment replacement operations can be performed.

4.3 Reset After Tripping

When a short circuit, overload or other faults occur in the circuit, the circuit breaker will trip automatically, The reset steps are as follows:

1）. First check and eliminate circuit faults (such as three-phase short circuit, load overload, etc.);

2）. Firmly pull the handle down to the "OFF" position to complete the mechanism reset;

3）. Then push the handle upward to the "ON" position to restore power supply.

5. Safety Precautions

5.1. It is strictly prohibited to use beyond the rated current and breaking capacity, otherwise it will cause frequent tripping, overheating and burning of the circuit breaker, and even lead to safety accidents.

5.2. After tripping, the fault must be eliminated first before resetting. Forcible closing is strictly prohibited to avoid equipment damage or secondary faults.

5.3. During maintenance, in addition to disconnecting the 3P circuit breaker, it is necessary to confirm that the upper main switch is disconnected to prevent accidental power supply; after maintenance, check the phase wire connection order to avoid reverse connection.

5.4. Regularly inspect the circuit breaker: check for abnormalities such as abnormal noise, terminal overheating, and loose handle. If a fault occurs, stop using it immediately and replace it. Do not disassemble or repair it by yourself.

5.5. It is not suitable for single-phase load circuits. For single-phase loads, 1P or 2P miniature circuit breakers are recommended.

6. Common Troubleshooting

6.1. Trips immediately after closing: mostly due to three-phase circuit short circuit or reverse phase wire connection. Check the wiring, downstream equipment and lines, and close after eliminating the short circuit fault.

6.2. Frequent tripping during normal use: load overload or undersized circuit breaker model. Reduce the total three-phase load or replace with a 3P circuit breaker with higher rated current.

6.3. Cannot close, handle stuck: the tripping mechanism is not reset or the fault is not eliminated. First pull to "OFF" to reset, check the fault and then try to close; replace if damaged.

6.4. Terminal overheating and burning smell: loose wiring or undersized wire diameter. Tighten the wiring screws after power off and replace with wires of appropriate diameter.

Product Operate Guide

# How to Use 2P Miniature Circuit Breaker

1. Scope of Application

2P MCB is suitable for single-phase 220V/230V and three-phase 380V/400V AC power systems, mainly used for:

- Household main incoming power switch

- High-power load circuits: air conditioners, water heaters, kitchen and bathroom sockets

- Circuits with high safety requirements

- General power and socket circuits in commercial and industrial places

2. Pre-installation Notes

- Installation must be performed under complete power-off condition. Live working is strictly prohibited.

- Confirm rated current, voltage and breaking capacity match the circuit requirements.

- Standard mounting on 35mm DIN rail in distribution box.

3. Wiring Method

2P circuit breaker controls both live wire (L) and neutral wire (N).

- Upper terminals: connect incoming L and incoming N

- Lower terminals: connect outgoing L and outgoing N

- Protective earth wire (PE) must be connected to the earth busbar separately, never connected to the breaker

4. Operation Instructions

Switching On

Push the operating handle upward to the ON position; both poles are switched on.

Switching Off

Pull the handle downward to the OFF position; both poles are disconnected.

Reset After Tripping

When the breaker trips due to fault, the handle stays in the OFF position:

1. Pull the handle fully down to OFF again

2. Push upward to ON to reset

5. Safety Precautions

- Do not use over rated current, which may cause frequent tripping or overheating.

- After tripping, check and eliminate circuit faults (short circuit, overload) before resetting.

- 2P MCB disconnects both L and N, making the circuit completely dead, which is safer for maintenance.

- Regularly check for abnormal heating, loosening or damage; replace the breaker if any fault occurs.

6. Troubleshooting

- Trips immediately after closing: short circuit in the circuit, check wiring and loads.

- Trips after working for a period: circuit overload, reduce load or use a higher rated breaker.

- Cannot be closed: internal mechanism fault, replace with a new unit.

Frequently Asked Questions (FAQs)

3P Miniature Circuit Breaker - Common Problems and Solutions

1. Trips immediately when closing

- Cause: Three-phase circuit short circuit, reversed phase wire connection (phase error), internal short circuit of downstream equipment

- Solution: After cutting off the power, check for short circuit faults in the three-phase line and downstream equipment, correct the phase wire connection sequence, and close the switch only after troubleshooting

2. Frequent tripping during normal use

- Cause: Overload of total three-phase load current, undersized circuit breaker (mismatched rated current), poor contact of a certain phase line

- Solution: Reduce the total three-phase load, replace the 3P circuit breaker with a larger rated current, check and fasten the terminal connections of each phase

3. Unable to close, handle stuck

- Cause: Tripping mechanism not reset, unaddressed three-phase circuit faults, damaged internal mechanical structure of the circuit breaker

- Solution: First firmly switch the handle to the "OFF" position to complete reset, check and eliminate short circuits, overloads and other faults; if it is still stuck, the internal structure is damaged and a new product needs to be replaced

4. Terminal overheating with burning smell

- Cause: Loose three-phase wiring, undersized wire diameter (mismatched with load current), poor terminal contact

- Solution: Immediately cut off the power, tighten the wiring screws, replace the wire with an appropriate diameter, clean the terminals and reconnect firmly

5. No tripping during short circuit/overload

- Cause: Damaged tripping mechanism, wrong selection of circuit breaker model (mismatched rated current/interrupting capacity), aged circuit breaker

- Solution: Immediately stop using and replace the circuit breaker, select a model with matching three-phase load current and interrupting capacity (6kA/10kA), and regularly replace aged components

6. Abnormal noise and vibration during operation

- Cause: Loose rail installation, unbalanced three-phase load, loose internal structure of the circuit breaker

- Solution: Fasten the circuit breaker installation screws, check and adjust the three-phase load balance, and replace the circuit breaker if the noise persists

7. Three-phase equipment fails to start normally, and the circuit breaker does not trip

- Cause: Incorrect phase wire connection sequence, open circuit of a certain phase line, poor contact of circuit breaker contacts

- Solution: After cutting off the power, check the three-phase wiring sequence, troubleshoot the open circuit of the phase line, and clean or replace the circuit breaker with poor contact