Description

The TERASAKI ESM-103J is a precision-engineered earth leakage (ground fault) relay designed to provide reliable personnel and equipment protection in low-voltage industrial, commercial, and infrastructure power systems. As part of TERASAKI’s renowned ESM series of residual current relays, the TERASAKI ESM-103J detects dangerous leakage currents to ground—often caused by insulation degradation, moisture ingress, or wiring faults—and triggers a trip signal to an associated circuit breaker or contactor to isolate the faulty circuit before damage or electric shock occurs.

Positioned as a modular, DIN rail-mounted protection device, the TERASAKI ESM-103J integrates seamlessly into control panels for applications ranging from water treatment plants to manufacturing lines. Unlike built-in RCDs, this relay separates the sensing unit from the switching mechanism, enabling flexible coordination with high-current breakers and remote monitoring via auxiliary contacts. The TERASAKI ESM-103J supports both AC and pulsating DC residual currents (Type A sensitivity), making it suitable for modern systems with variable frequency drives (VFDs) or switched-mode power supplies that generate non-sinusoidal leakage waveforms.

Widely deployed across Asia and increasingly recognized globally for its robustness and accuracy, the TERASAKI ESM-103J exemplifies TERASAKI’s commitment to electrical safety through intelligent, field-proven design—offering adjustable trip thresholds, clear status indication, and long-term stability in harsh electrical environments.

Technical Specifications

Main Features and Advantages

High-sensitivity, field-selectable trip levels:
The TERASAKI ESM-103J allows users to choose between 30 mA (for life protection in wet areas), 100 mA (fire prevention in dry circuits), and 300 mA (equipment protection in motor or transformer feeds)—all via a simple front-panel rotary switch. This eliminates the need to stock multiple relay models and enables on-site adaptation during commissioning or system modifications.

Universal power supply and Type A detection:
Unlike basic relays limited to pure AC leakage, the TERASAKI ESM-103J complies with IEC 60755 Type A requirements, meaning it reliably detects both sinusoidal AC and half-wave rectified DC leakage—common in circuits with VFDs, LED drivers, or IT equipment. Its wide 100–240 VAC/DC supply range ensures compatibility with global control panel standards without requiring external power adapters.

Clear diagnostics and manual test function:
Equipped with a green “ON” LED and red “TRIP” indicator, the TERASAKI ESM-103J provides immediate visual status feedback. A built-in TEST button simulates a leakage fault to verify the entire protection chain—including the relay, signaling contacts, and downstream breaker—without external tools, simplifying compliance with safety audit requirements.

Robust mechanical and electrical design:
Housed in a flame-retardant (UL 94 V-0) polycarbonate case, the TERASAKI ESM-103J withstands voltage surges, humidity, and continuous operation in industrial environments. Gold-plated signal contacts ensure long-term reliability for alarm or interlock circuits, while the compact 1-module width conserves valuable panel space.

Seamless integration with contactors and breakers:
The TERASAKI ESM-103J does not interrupt power directly; instead, it sends a trip command to a shunt coil or undervoltage release on a molded-case circuit breaker (MCCB) or contactor. This architecture supports high-current circuits (up to thousands of amps) and enables centralized ground fault coordination in multi-level distribution systems.

Application Field

The TERASAKI ESM-103J is extensively used in water and wastewater treatment facilities, where ground faults in submersible pumps or chemical dosing systems pose both safety and environmental risks. By detecting small leakage currents early, the TERASAKI ESM-103J prevents motor burnout and avoids uncontrolled discharge due to pump failure.

In HVAC and chiller plant rooms, the TERASAKI ESM-103J protects compressor motors and fan arrays from insulation breakdown caused by condensation or vibration. Its Type A sensitivity is critical here, as modern inverters generate DC-like leakage that standard Type AC relays would miss—ensuring uninterrupted climate control in hospitals, data centers, and cleanrooms.

Industrial machinery builders integrate the TERASAKI ESM-103J into OEM control panels for packaging lines, CNC machines, and robotic cells to meet international safety standards (e.g., IEC 60204-1). The relay’s signal contacts can trigger a safety PLC input, enabling coordinated shutdowns beyond simple power disconnection.

For building management systems in commercial complexes, the TERASAKI ESM-103J monitors lighting circuits, elevator controls, and emergency power distribution—providing fire-risk mitigation through 300 mA setting while maintaining selectivity with downstream 30 mA RCDs in socket outlets. Its DIN rail form factor and universal power make retrofitting into legacy panels straightforward, extending the life of existing infrastructure without full rewiring.

Related Products

• ESM-102J: Lower-cost variant with fixed 30 mA setting and no DC sensitivity (Type AC only)

• ESM-203J: Higher-end model with time-delay options (S-type) for selective coordination in cascaded systems

• TMAX T4N: TERASAKI molded-case circuit breaker often paired with ESM-103J via shunt trip coil

• RME3-32: Auxiliary contact block for TERASAKI breakers to provide feedback to the ESM-103J loop

• ESR-103J: Remote test/reset module allowing external operation of the ESM-103J without panel access

• ELR-103: Competitor equivalent from Mitsubishi Electric—similar specs but different mounting footprint

• GDA203: Schneider Electric’s Vigilohm relay—functional alternative with Modbus communication option

Installation and Maintenance

Pre-installation preparation: Before installing the TERASAKI ESM-103J, verify that the panel’s control power matches the relay’s 100–240 VAC/DC rating. Ensure the toroidal zero-sequence current transformer (ZCT) is correctly sized for the conductor bundle and that all phase and neutral conductors pass through the core—ground wires must be excluded to avoid false tripping. Mount the TERASAKI ESM-103J on a standard 35 mm DIN rail with adequate clearance for heat dissipation and front-panel access. Connect the ZCT output leads to terminals “T1” and “T2” per polarity markings.

Maintenance recommendations: Periodically press the TEST button on the TERASAKI ESM-103J during scheduled outages to validate trip functionality and downstream breaker response. Inspect the ZCT for physical damage or loose mounting, as mechanical stress can alter sensitivity. If nuisance tripping occurs, use a leakage clamp meter to measure actual residual current and confirm whether the setting (30/100/300 mA) is appropriate for the load type. Avoid exposing the TERASAKI ESM-103J to condensation or conductive dust; in harsh environments, consider installing it within an IP54-rated enclosure. Always replace the unit if the self-test fails or if the housing shows signs of thermal discoloration.