Power Factor Based Regulation

Motor Thermal Model

Many motor failures are directly or indirectly related to, or caused

by, extensive heating of the different motor parts involved in

electromechanical operation. Proven through several generations of GE’s

Multilin motor relays, an enhanced thermal model is used in the 869 relay

with seven major features:

Motor thermal limit curves – NEMA® standard, voltage dependent and

customized motor curves

• IEC 60255-8 thermal overload curves

• Smoothing filter for cyclic loads

• Current unbalance biasing

• Independent running and stopped exponential cooling curves

• Optional RTD biasing of the thermal model to adapt to real-time

temperature measurements

• Compensation for hot/cold motor condition

The flexibility of the Multilin 869 thermal models allows for proper set up

and performance for applications, including high inertia and cyclic loads.