CHAPTER 5: SETTINGS
GROUPED ELEMENTS
M60 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
5-195
5
Once the motor load current exceeds the overload level (FLA x overload factor), it enters an overload phase; that is, the
heat accumulation becomes greater than the heat dissipation. The M60 thermal model reacts by incrementing the thermal
capacity used (TCU) at a rate dependent on the selected thermal curve and overload level. When the thermal capacity
reaches 100%, the
MOTOR THERMAL OP
operand (typically configured to trip the motor) is set. This operand remains asserted
until TCU decays to the level that permits a new motor start. For details, see the description of the
START INHIBIT TCU
MARGIN
setting in this section.
THERMAL MODEL CURVE
— The thermal model curve determines the thermal limit overload conditions that can damage the
motor. This curve accounts for motor heating in both the stator and rotor during stall, acceleration, and running conditions.
The overload curve can take one of the following six formats: Motor, FlexCurve A, FlexCurve B, FlexCurve C, FlexCurve D, or
IEC. The selected curve can also serve as a base for a voltage dependent overload curve if the
VOLTAGE DEPENDENT
FUNCTION
setting is “Enabled.” The algorithm uses memory in the form of a register called Thermal Capacity Used. This
register is updated every power cycle using the following equation:
Eq. 5-7
where time_to_trip represents the time coordinate on the time-current overload curve, corresponding to the equivalent
motor current detected within any power cycle period of motor overload. Always set the overload curve slightly lower than
the thermal limits provided by the motor manufacturer. This ensures that the motor is tripped before the thermal limit is
reached.
The “Motor” curve is based on typical motor thermal limit curves and is normally used for standard motor applications (see
the Standard Motor Curves figure and Standard Curve Multipliers table that follow). The pickup level for the “Motor” curve is
calculated as
MOTOR OVERLOAD FACTOR
setting (OF) times the
MOTOR FULL LOAD AMPS
setting (FLA). The
MOTOR FULL LOAD
AMPS
(FLA) setting can be found in the
SYSTEM SETUP
MOTOR
menu.
Содержание M60
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Страница 14: ...1 4 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL FOR FURTHER ASSISTANCE CHAPTER 1 INTRODUCTION 1 ...
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Страница 602: ...9 4 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL SATURATION DETECTOR CHAPTER 9 THEORY OF OPERATION 9 ...
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