High Speed Acceleration; High Speed Undercurrent - GE 339 Instruction Manual

CHAPTER 6: SETPOINTS
High speed
acceleration
High speed
undercurrent
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
When two-speed functionality is enabled, the main acceleration timer is used for low
speed starting (a start in low speed from a stopped condition). Two additional acceleration
timers are provided for high speed starting. One timer is for a start in high speed from a
stopped condition, another timer is for the transition from low speed to high speed.
Selection of acceleration timers is as described in the Acceleration section of this manual.
If two-speed functionality is enabled, the 339C relay relies on the motor speed indication to
switch the undercurrent settings as per the motor running speed, so the main
Undercurrent Protection element is only active when the motor is running at low speed,
and the High Speed Undercurrent Protection element is only active when the motor is
running at high speed. If two-speed functionality is not deployed, only the main Short
Circuit is active, and the High Speed Short Circuit is disabled.
PATH:
SETPOINTS > S3 PROTECTION > TWO SPEED MOTOR > HIGH SPEED U/CURR
U/CURR ALARM FUNC
Range: Disabled, Enabled
Default: Disabled
This setting is used to enable the High Speed Undercurrent Alarm function.
BLK U/C ON START
Range: 0 to 600 s in steps of 1 s
Default: 0 s
This setting is used to specify a time delay to block undercurrent function when the
motor is starting to High Speed. If this setting is programmed as 0, the undercurrent
function will not be blocked from start.
U/CURR ALARM PKP
Range: 0.10 to 0.95xFLA in steps of 0.01xFLA
Default: 0.70xFLA
This setting specifies a pickup threshold for the Alarm stage. This threshold should be set
lower than motor load current during normal operation.
U/CURR ALARM DELAY
Range: 1.00 to 60.00 s in steps of 0.01 s
Default: 1.00 s
This setting specifies a time delay for the Alarm stage. This time delay should be set long
enough to overcome short lowering of the current such as during system faults.
U/CURR TRIP FUNC
Range: Disabled, Enabled
Default: Disabled
This setting is used to enable the High Speed Undercurrent Trip function.
U/CURR TRIP PKP
Range: 0.10 to 0.95xFLA in steps of 0.01xFLA
Default: 0.60xFLA
This setting specifies a pickup threshold for the Trip stage. This threshold should be set
lower than the threshold for the Alarm stage.
U/CURR TRIP DELAY
Range: 1.00 to 60.00 s in steps of 0.01 s
Default: 1.00 s
This setting specifies a time delay for the Trip stage. This time delay should be set long
enough to overcome short lowering of the current such as during system faults.
S3 PROTECTION
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