Technical Specifications

Main Features and Advantages

One device, one calibration, one fault trail.​ The single biggest win of the GE MMII-PD-1-2-120​ is that protection, control and recording now share a single set of inputs and a single configuration. There is no longer a bimetal element set to 1.05 × FLA, a separate phase-loss relay with its own CT and a timer with its own calibration drift. Set the motor FLA and the CT ratio once in EnerVista or from the keypad, and every element — overload, unbalance, stall, ground fault and temperature — scales from that same truth. When a trip happens, the LCD shows not just “trip,” but which element, at what current, and with how much thermal capacity was left. That is the difference between a ten-minute fix and a day-long autopsy.Option 1 and Option 2 are why this exact suffix matters.​ A plain MMII-PD-120 is not the same spare. The -1-​ in the MMII-PD-1-2-120​ brings the process-control and enhanced-diagnostics package: the 4–20 mA process input, programmable process inputs, undervoltage auto-restart and the richer event set that lets the relay decide “restart the pump after the brownout” instead of making the DCS write that logic. The -2-​ adds the ground-fault element, the locked-rotor/stall logic and the thermistor/RTD winding input. Together they turn the unit from a smarter overload relay into a small protection scheme. Swapping in a lesser suffix silently loses functions the rest of the starter and the DCS were counting on.Thermal modelling instead of thermal guessing.​ The I²t engine inside the GE Multilin MMII-PD-1-2-120​ does not trip on a fixed current threshold; it integrates heating against the motor’s own thermal inertia, counts starts, tracks cool-down, and distinguishes a long steady overload from a start that is still inside the allowable duty. The front panel’s “thermal capacity %” is genuinely useful on a hot day — an operator can see a pump drifting toward 90% and intervene before the relay makes the decision for him. For a motor on a cyclic duty, that visibility alone prevents the slow, cumulative cooking that never shows up as a single dramatic trip.Ground fault and stall without the usual blind spots.​ Ground-fault protection in the MM2 reads the zero-sequence path and is shaped independently of the phase overcurrent, so a low-level insulation leak is caught long before it becomes a phase-to-ground fault that takes out the bucket. The stall/locked-rotor element, meanwhile, is start-aware: it rides through the high inrush of a healthy acceleration and only asserts once the motor should already be at speed. That discrimination is what stops the classic complaint — “the overload trips every time we start the pump” — because in almost every such case the old device was timing the start as a fault, and the MMII-PD-1-2-120​ is configured to understand it.A 120 VAC control world, no transformer required.​ The suffix is a constraint, and it is also a convenience. In North American and export MCCs the 120 VAC control circuit is already there, so the GE MMII-PD-1-2-120​ lands directly on the control transformer secondary with no buck-boost, no DC supply and no 240 VAC run back to the panel. The trade-off is absolute: do not fit a 240 VAC unit here and do not “just try” a 120. The supply tolerance is 80–135 VAC; outside that, the relay may power the display while the outputs misbehave, which is worse than a clean failure.Modbus out, guessing gone.​ The RS-485 port is not a marketing port. Once landed on a Modbus master — a GE DCS, a PLC or a small gateway — the relay hands up phase currents, thermal capacity, ground-fault current, alarm and trip status, run hours and start count. That stream is what turns a motor into a predictably maintained asset: trend the thermal capacity, watch the start count climb, catch the ground-fault residual rising over a wet season. It also means the DCS can inhibit a restart or log an operator action without anyone touching the bucket door.