Schneider Electric EOCR-PMZ Motor Protection Relay

The Schneider Electric EOCR-PMZ (EOCRPMZ) is an electronic motor protection relay designed to prevent damage from overload, phase loss, phase imbalance, and ground faults. It is part of the EOCR (Electronic Over Current Relay) series, offering adjustable trip settings and a compact design for motor control centers and industrial machinery. The relay provides both manual and automatic reset options and features a digital display for monitoring current values.

Technical Specifications

Current range: adjustable from 0.5 to 60A (using internal CT and external CT for higher ranges up to 800A). Control voltage: 24-240V AC/DC (universal). Output contacts: 1 SPST (95-96) normally closed (trip), 1 SPST (97-98) normally open (alarm). Trip time characteristics: adjustable time limit (class 5, 10, 20, 30) or inverse time. Trip accuracy: ±5% of set value. Phase imbalance trip: adjustable 5-30% (default 15%). Ground fault trip sensitivity: 0.5-5A (optional model specific, not on all PMZ). Reset method: manual (via front button or remote) or automatic (selectable). Display: 7-segment LED for current (A) and fault codes.

Key Features

• Electronic overload protection for 3-phase motors

• Adjustable current 0.5-60A (direct connection)

• Protection functions: overload, phase loss, phase imbalance, reverse phase (optional), ground fault (select models)

• Digital LED display showing actual RMS current per phase

• Time-limit or inverse-time tripping characteristics

• Output relay for trip and alarm indication

• Manual/Automatic reset selection

• Self-diagnostics and memory for last fault

• Mounts on DIN rail or panel via adapter

Protection Functions

Overload: Based on thermal model with selectable trip classes. Phase loss: Detects loss of any phase and trips within 4 seconds. Phase imbalance: Trips if imbalance exceeds set percentage for 8 seconds. Ground fault (GF): Detects leakage current to ground (sensitivity adjustable). Reverse phase: Protects against incorrect phase sequence (enabled on some models). The relay continuously measures RMS current via internal current transformers.

Configuration and Setting

DIP switches and potentiometers on the front panel set: current range (0.5-6A or 5-60A), trip class (5,10,20,30), overload trip current (set as multiple of motor FLA), ground fault sensitivity (if present). Digital display shows actual current by pressing the test button. To set, rotate the dial to match the motor's full load ampere value. The LED displays "A" when measuring, and fault codes (e.g., "OL" for overload, "PL" for phase loss) when tripped.

Wiring and Installation

The EOCR-PMZ connects directly in series with the motor's three-phase lines (L1, L2, L3) via terminals 1-2-3-4-5-6. The current transformers are built-in. Control voltage (A1, A2) must be supplied from a separate source (24-240V AC/DC). Output relay contacts (95-96) are normally closed and open when a fault occurs; they should be connected in series with the contactor coil circuit. The alarm contact (97-98) can be used for remote indication. The relay should be mounted in a dry, non-condensing environment. For motors >60A, use external CTs (5A secondary) and set the CT ratio accordingly.

Applications

The EOCR-PMZ is used in motor control centers, pumps, fans, compressors, conveyors, and any three-phase motor where thermal overload relays are insufficient due to phase loss or imbalance sensitivity. It is especially useful in applications with frequent starting, where ambient temperatures vary.

Testing and Diagnostics

A built-in test button allows simulating overload conditions and verifying relay operation. The digital display cycles through phase currents (L1, L2, L3). In case of a trip, the display shows the fault code and the current value at trip. The relay retains the last fault code until reset. Reset can be done manually by pressing the reset button on the front or electrically via the remote reset terminals (if available).

Environmental and Standards

The EOCR-PMZ complies with IEC 60947-4-1, UL 508, and CSA C22.2. It is CE marked. Operating temperature: -20°C to +60°C; storage -40°C to +80°C. Humidity: 30-85% RH non-condensing. Dielectric strength: 2000V AC for 1 minute. Vibration: 0.5g (10-55 Hz).

Conclusion

The Schneider Electric EOCR-PMZ provides comprehensive electronic motor protection in a compact, easy-to-setup package. Its digital display, adjustable protection parameters, and robust design make it a reliable upgrade from traditional thermal overload relays.