Siemens HJD63F400

Technical Specifications​

Frame JD, type HJD6/HJXD6. Rated current 400 A maximum frame rating, thermal setting range published for compatible JD trip units from 200 A to 400 A. Three poles. Voltage rating 600 V AC, 50/60 Hz; DC rating up to 500 V DC depending on configuration. Interrupting rating 35 kA at 600 V AC, 65 kA at 480 V AC, 100 kA at 240 V AC under UL; IEC values 42 kA at 500 V AC, 65 kA at 380/415 V AC, 100 kA at 220/240 V AC. Trip system thermal-magnetic with fixed thermal and adjustable magnetic characteristics. Terminals line and load side, kit TA2J6500, copper 3/0 AWG to 500 kcmil, aluminum 4/0 AWG to 500 kcmil. Calibration temperature 40 °C. Dimensions approximately 7.5 in width, 11.0 in height, 4.0 in depth; some mounted-assembly listings show greater overall envelope. Standards UL 489 and IEC 60947-2.

Function Features​

Thermal element provides inverse-time overload protection. Magnetic element provides fast instantaneous short-circuit protection. High interrupting structure reduces let-through energy. Bolt-on or panel mounting according to enclosure design. Optional auxiliary contacts, shunt trip, bell alarm and lug kits can be added for status and remote control.

Application Scenarios​

Main and branch feeder protection in industrial plants, commercial buildings and utilities. Switchgear and motor control center incoming protection. Large HVAC, pump, compressor and general three-phase 400 A distribution circuits. Retrofit of existing Siemens SENTRON JD installations and service replacement of matched frame types.

Performance Parameters​

Sustained current 400 A at 40 °C calibration without forced cooling when applied within conductor and enclosure ratings. Short-circuit performance defined by the AIC values above and by upstream system fault current. Mechanical operating life and electrical endurance follow Siemens JD catalog limits; periodic verification is required in high-cycling duty.

Material Composition​

Molded thermoset or engineering plastic case, copper alloy current-carrying parts, silver-based contact surfaces, steel operating mechanism, arc-chute insulation plates, terminal lugs in tinned copper or aluminum-compatible alloy and labeling with thermal calibration elements.

Structural Characteristics​

Three-pole insulated case with central trip unit compartment, independent operating handle, line and load terminal compartments and arc interruption chambers. Removable front cover provides access to trip adjustments. Mounting holes or bolt-on feet suit switchboard panels. Status position indicates ON, OFF and tripped.

Working Principle​

Load current passes through each pole and the thermal element. During sustained overload, the thermal mechanism heats and releases the latch after an inverse-time delay proportional to current. During a short circuit, the magnetic actuator senses high current and trips the mechanism instantly, opening contacts inside arc chutes to extinguish the arc and isolate the fault.

Installation Requirements​

De-energize and apply lockout/tagout before installation. Verify frame type, trip rating, lug kit and terminal set match the existing panel. Mount on a rigid grounded structure with adequate clearances. Torque line and load lugs to Siemens values using calibrated tools. Use copper or aluminum conductors within the approved range and apply antioxidant compound for aluminum if required. Confirm enclosure ventilation, ambient temperature derating and upstream fault current do not exceed 35/65/100 kA ratings.

Usage Precautions​

Do not operate beyond 600 V AC or the approved DC rating. Confirm whether the purchased unit includes thermal-magnetic trip unit and lugs, because some listings supply frame-only packages. Reset only after the fault cause is removed. Inspect contact wear, lug tightness and trip calibration during planned maintenance. Use qualified electrical personnel and comply with NEC, local codes and lockout procedures.