EOCR-PMZ (panel embedded) and EOCR-PFZ (embedded) motor comprehensive protector

EOCR-PMZ/PFZ Motor Protector: Comprehensive Protection and Intelligent Diagnosis in Practical Use

In the field of industrial motor control, the selection and configuration of protective relays are directly related to equipment lifespan and production continuity. The EOCR-PMZ/PFZ series electronic overload relays launched by Schneider (formerly Sanhe, South Korea) have become the first choice for many engineers to upgrade motor protection solutions due to their integrated functions of overcurrent, undercurrent, ground fault, current transmission, as well as intuitive digital display and programmable features. This article will systematically review the entire application process of EOCR-PMZ/PFZ from core functions, parameter settings, wiring points to selection and ordering, helping you quickly deploy and avoid common pitfalls in renovation or new projects.

Overview of core functions: Integrated protection with multiple functions for one machine

The EOCR-PMZ (window type) and EOCR-PFZ (terminal type) products share the same set of protection logic and operation interface, with the only difference being the structural form of the current detection terminal. Its core advantage lies in integrating protection functions such as overload, underload, ground fault, phase sequence, phase loss, imbalance, locked rotor, and blocking, and supporting 4-20mA current transmission output, greatly simplifying the number of components and wiring complexity inside the control cabinet.

1.1 Automatic cycle display and manual locking

The front of the device is equipped with a 5-digit 7-segment LED digital tube, coupled with a phase indicator light, which automatically displays the L1, L2, L3 three-phase current and leakage current every 5 seconds by default. During on-site inspection, pressing the SET button can switch to manual cycle mode, locking a certain phase or leakage value in sequence with each press, making it easier to observe specific parameters. Long press or press the reset button again to return to automatic mode - this design is particularly useful for debugging or troubleshooting.

1.2 Wide Range and External CT Expansion

Direct connection: The body provides a wide range setting of 0.5~60A (selected through internal dialing or menu), suitable for various wiring methods such as 5-hole core through type (0.1~2.0A), 2-hole type (0.25~5.0A), etc.

External CT extension: With the standard 5A output current transformer (CT), the range can be extended to 3600A. Users only need to set the CT ratio in the parameter Ct (for example, 200:5 is set to 200) to achieve precise protection for high current motors.

1.3 Fault records and pre maintenance reminders

Relays can remember the reasons for the last three trips and the current values of each phase at the time of the trip. Even if the power is disconnected and reconnected, the records will not be lost. In addition, the built-in cumulative running time timer (up to 65500 hours) and adjustable operation time reminder (1~9990 hours), when the motor reaches the set time, the panel will alternately display the current and remaining time, prompting maintenance operations such as bearing replacement - this is an excellent auxiliary means for preventive maintenance strategies.

Detailed explanation of protection function: engineering significance behind each parameter

2.1 Overcurrent Protection (OC) - Three optional characteristic curves

Overcurrent is the most common fault of motors. EOCR-PMZ/PFZ provides three action characteristics:

Definite (dE): After the current exceeds the set value, it trips after a fixed delay of ot (0.2-30 seconds). Suitable for situations where short-term overload is allowed but high delay accuracy is required.

Inverse, In: According to the I ² t characteristic, the larger the current, the faster the action, with a delay range of 1-30 seconds. Consistent with the behavior of thermal relays, it is more in line with the motor's thermal tolerance curve.

Thermal Inverse (th): Adding thermal memory function on the basis of inverse time. The heat generated during the operation of the motor will be accumulated, and the accumulated heat value will be automatically reset within 20 minutes after shutdown. If restarted immediately in a hot state, the protection action time will be shorter, simulating a real hot state.

Engineering suggestion: For ordinary fans and water pumps, dE or In can be used; for equipment that frequently starts and stops or starts under heavy loads, th is recommended to avoid the protection value set in cold state being insufficient to protect the motor in hot state.

2.2 Undercurrent protection (UC) - prevents idling or belt breakage

When the current is lower than the set value (which can be set to 0.5A to 0.1A less than the overcurrent value) and the duration exceeds Ut (0.5-30 seconds), the relay will activate. Typical application scenarios: Water pump idling, belt slipping or breaking, compressor lacking refrigerant. Attention: The undercurrent value and overcurrent value cannot be equal or higher than the overcurrent value, otherwise they cannot be set.

2.3 Grounding Fault Protection (EC) - Zero Sequence Current Detection