Square D LJA36400CU44X PowerPact L 400A 3-Pole 600V I-Line Molded Case Circuit Breaker
Square D LJA36400CU44X PowerPact L 400A 3-Pole 600V I-Line Molded Case Circuit Breaker
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Square D LJA36400CU44X – PowerPact L Molded Case Circuit Breaker
The Square D LJA36400CU44X (by Schneider Electric) is a high-performance 400-Amp, 3-Pole, 600V Molded Case Circuit Breaker from the PowerPact L family. Designed for demanding commercial and industrial power distribution systems, this I-Line style plug-in breaker combines advanced solid-state protection with a 100% continuous duty rating — making it one of the most reliable solutions for switchboards and panelboards operating at 600VAC.
Key Features
- 400A Continuous Rating (100% Rated) – Operates at full ampacity without derating
- MicroLogic 6.3A Electronic Trip Unit – Solid-state LSIG protection: Long-Time, Short-Time, Instantaneous, and Ground Fault
- I-Line Style Plug-In Mounting – Fast, tool-free installation into compatible Square D I-Line panelboards
- Built-In Ammeter Display – Real-time current monitoring via non-interchangeable MicroLogic Ammeter
- Push-to-Trip Test Button – Manual trip verification without load disconnection
- Trip-Free Mechanism – Breaker trips even if handle is held or blocked
- Multiple Certifications – UL 489, CSA, IEC, CE, CCC, NOM (NMX), NEMA compliant
- Current Limiting – Reduces let-through energy to protect downstream equipment
Technical Specifications
| Part Number | LJA36400CU44X |
| Manufacturer | Square D / Schneider Electric |
| Product Family | PowerPact L |
| Frame Type | LJA |
| Number of Poles | 3 (also usable in 2-pole applications) |
| Ampere Rating | 400A |
| Voltage Rating | 600V AC |
| Trip Unit | MicroLogic 6.3A – Electronic (Solid State), LSIG |
| Mounting Type | I-Line Style Plug-In |
| Connection (Line Side) | I-Line Plug-In |
| Connection (Load Side) | Lug Terminals (AWG 3/0 – 500 kcmil, Al/Cu) |
| Interrupting Rating @ 240V AC | 100 kAIC |
| Interrupting Rating @ 480V AC | 65 kAIC |
| Interrupting Rating @ 600V AC | 25 kAIC |
| DC Interrupting Rating | 20 kA @ 250V DC |
| Duty Rating | 100% Rated |
| Phase | 3-Phase |
| Approvals / Certifications | UL 489, CSA, IEC 60947-2, CE, CCC, NOM, NEMA |
| Dimensions | 14.7"H x 5.94"W x 6.61"D |
| Condition | New |
Trip Functions – LSIG Protection Explained
The MicroLogic 6.3A trip unit provides four layers of protection in a single breaker:
- L – Long-Time: Protects against sustained overloads
- S – Short-Time: Allows temporary inrush currents while still protecting against faults
- I – Instantaneous: Immediately trips on high-magnitude short circuits
- G – Ground Fault: Detects and interrupts ground fault currents to protect personnel and equipment
Typical Applications
- Commercial buildings and industrial facilities
- Main and feeder circuit protection in Square D I-Line switchboards
- Motor control centers (MCCs)
- Data centers and critical infrastructure
- Construction and utility power distribution
- Heavy manufacturing and process equipment
Why Choose the Square D LJA36400CU44X?
When uptime and safety are non-negotiable, the PowerPact L family delivers. The LJA36400CU44X offers precise electronic overcurrent protection with an integrated ammeter — eliminating the need for separate metering in many applications. Its I-Line plug-in design dramatically reduces installation time, and its 100% continuous duty rating means no derating on the job site.
Backed by Schneider Electric's global engineering and certified to UL, CSA, IEC, and international standards, this breaker is built to perform in the most demanding environments.
Frequently Asked Questions
What is the Square D LJA36400CU44X?
The LJA36400CU44X is a 400-Amp, 3-Pole, 600V AC molded case circuit breaker from Square D's PowerPact L series. It features an I-Line plug-in mount and a MicroLogic 6.3A solid-state LSIG trip unit with built-in ammeter.
What does "I-Line style plug-in" mean?
I-Line is Schneider Electric's proprietary bus connection system for PowerPact circuit breakers. It allows the breaker to plug directly into a compatible Square D I-Line panelboard without additional wiring on the line side — enabling faster, safer installation.
Is the LJA36400CU44X 100% rated?
Yes. This breaker is 100% continuously rated, meaning it can operate at its full 400A ampacity indefinitely without derating — unlike standard 80% rated breakers that must be derated to 320A in continuous operation.
What is LSIG protection?
LSIG stands for Long-Time, Short-Time, Instantaneous, and Ground Fault — the four protective trip functions built into the MicroLogic 6.3A trip unit. Together, they provide comprehensive protection against overloads, short circuits, and ground faults.
What certifications does this breaker carry?
The LJA36400CU44X is certified by UL (UL 489), CSA, IEC (IEC 60947-2), CE, CCC, NOM, and NEMA — making it suitable for use in North American and international electrical systems.
Can this breaker be used in 2-pole applications?
Yes. The LJA36400CU44X can be configured for 2-pole applications as well as its standard 3-pole configuration.