CHAPTER 5: SETTINGS
GROUPED ELEMENTS
M60 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
5-205
5
Figure 5-105: RTD bias curve
START INHIBIT TCU MARGIN
— This setting prevents starting of a motor if there is insufficient thermal capacity available for a
successful start. The motor start inhibit logic algorithm is defined by
MOTOR START INHIBIT MARGIN
setpoint. If
MOTOR START
INHIBIT MARGIN
is set to “0”, the
MOTOR START INHIBIT
FlexLogic operand is asserted only when motor is tripped by thermal
protection (TCU = 100%). After being asserted, the
MOTOR START INHIBIT
operand resets and a new motor start is permitted
when TC
used
decays to a level of 15%. The thermal lockout time is calculated as follows.
Eq. 5-20
where
TCU
start
is the thermal capacity level when the
MOTOR START INHIBIT
operand is asserted
TCU
end
is the thermal capacity level when the
MOTOR START INHIBIT
operand is reset
τ
is the
COOL TIME CONSTANT STOPPED
setpoint
To calculate the thermal lockout time for the case when
MOTOR START INHIBIT MARGIN
is set to “0,” the following TCU values
are to be applied to the previous equation: TCU
start
= 100% and TCU
end
= 15%.
If
MOTOR START INHIBIT MARGIN
is greater than “0,” the
MOTOR START INHIBIT
operand is asserted either when the motor is
tripped by thermal protection (TCU = 100%) or tripped/stopped for any other reason (TCU < 100%).
Each time the motor is tripped/stopped by a means other than thermal protection (TCU < 100%) the available thermal
capacity (100% – TCU) is evaluated and compared to the TC required for starting the motor. If the available thermal
capacity is not sufficient to perform a new motor start, then the
MOTOR START INHIBIT
operand is asserted. The thermal
capacity required for starting the motor (TCU
onStart
) is defined from the following equation:
Eq. 5-21
where
TCU
margin
is the relay setpoint
TCU
maxStart
is the maximum thermal capacity value from the last five successful motor starts
The relay monitors motor starting and captures the TCU for each successful start. The largest value from the last five starts
is used in the start inhibit calculation.
If the motor is tripped or stopped by a means other than thermal protection (TCU < 100%), the
MOTOR START INHIBIT
operand is not asserted and a new start is permitted. There is a potential risk in this situation to trip out the motor
by thermal protection during the new start.
Содержание M60
Страница 9: ...TABLE OF CONTENTS M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL ix INDEX ...
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Страница 14: ...1 4 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL FOR FURTHER ASSISTANCE CHAPTER 1 INTRODUCTION 1 ...
Страница 208: ...4 88 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL FLEXLOGIC DESIGN USING ENGINEER CHAPTER 4 INTERFACES 4 ...
Страница 494: ...5 286 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL CONTROL ELEMENTS CHAPTER 5 SETTINGS 5 Figure 5 158 Time out mode ...
Страница 552: ...5 344 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL TESTING CHAPTER 5 SETTINGS 5 ...
Страница 596: ...7 14 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL TARGETS MENU CHAPTER 7 COMMANDS AND TARGETS 7 ...
Страница 602: ...9 4 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL SATURATION DETECTOR CHAPTER 9 THEORY OF OPERATION 9 ...
Страница 652: ...C 6 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL COMMAND LINE INTERFACE APPENDIX C COMMAND LINE INTERFACE C ...
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