GE 469 Instruction Manual

Also see for Masoneilan 469 Series: Instruction manual Instruction manual Communications guide Instruction manual Instruction manual

Contents

CHAPTER 5: SETTINGS469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL 5–39and the MOTOR THERMAL CAPACITY USED should be zero. If the motor is in overload, oncethe thermal capacity used reaches 100%, a trip will occur. The THERMAL CAPACITY ALARMmay be used as a warning indication of an impending overload trip.5.6.3 Overload Curve SetupOverviewThe overload curve accounts for motor heating during stall, acceleration, and running inboth the stator and the rotor. The OVERLOAD PICKUP LEVEL settings dictates where therunning overload curve begins as the motor enters an overload condition. This is useful forservice factor motors as it allows the pickup level to be defined. The curve is effectively cutoff at current values below this pickup.Motor thermal limits consist of three distinct parts based on the three conditions ofoperation: locked rotor or stall, acceleration, and running overload. Each of these curvesmay be provided for a hot and a cold motor. A hot motor is defined as one that has beenrunning for a period of time at full load such that the stator and rotor temperatures havesettled at their rated temperature. A cold motor is a motor that has been stopped for aperiod of time such that the stator and rotor temperatures have settled at ambienttemperature. For most motors, the distinct characteristics of the motor thermal limits areformed into a smooth homogeneous curve. Sometimes only a safe stall time is provided.This is acceptable if the motor has been designed conservatively and can easily perform itsrequired duty without infringing on the thermal limit. In this case, the protection can beconservative and process integrity is not compromised. If a motor has been designed veryclose to its thermal limits when operated as required, then the distinct characteristics ofthe thermal limits become important.The 469 overload curve can take one of three formats: Standard, Custom Curve, or VoltageDependent. Regardless of the selected curve style, thermal memory is retained in theA1 STATUS Z MOTOR STATUS ZV MOTOR THERMAL CAPACITY USED register. This register isupdated every 100 ms using the following equation:(EQ 5.1)where: time_to_trip = time taken from the overload curve at I eq as a function of FLA. Theoverload protection curve should always be set slightly lower than the thermal limitsprovided by the manufacturer. this will ensure that the motor is tripped before the thermallimit is reached.Standard Overload CurvesIf the SELECT CURVE STYLE is set to “Standard” in the Thermal Model, only the followingsettings will appear:PATH: SETTINGS ZV S5 THERMAL MODEL ZV OVERLOAD CURVE SETUPTC used at t TC used at t 100ms–100 mstime to trip--------------------------- 100%×+=OVERLOAD [STANDARD OVERLOADCURVE NUMBER: 4Range: 1 to 15 in steps of 1. Seen only ifStandard curve is selected.