Immediate Overload; Mechanical Jam - GE 239 Instruction Manual

4.5.3

Immediate Overload

4.5.4

Mechanical Jam

4–36
Courtesy of NationalSwitchgear.com
• PHASE S/C DELAY: The trip can be instantaneous (no intentional delay) or can be
delayed by up to 60000 ms to prevent nuisance tripping or allow co-ordination with
associated system switchgear. The
setpoint represents the intentional delay added to the detection
C\PHASE S\C DELAY
and output relay activation delays of the 239. When this setpoint is set to
will trip within 45 ms of the onset of the short circuit. Both the short circuit trip level
and time delay should be set to co-ordinate with other system protective relays to
minimize equipment shutdown during a high current fault.
• IMMEDIATE OVERLOAD ALARM: When the average phase current exceeds the full
load current (FLC) setpoint the phase timed overload protection begins timing. This will
eventually lead to a trip unless the overload disappears. Immediate overload warning
can be used to alert an operator or to produce an alarm output using this setpoint.
This feature should be set to off for systems that experience overloads as part of
normal operation such as crushers.
• IMMEDIATE OVERLOAD PICKUP: The immediate overload pickup setpoint is adjustable
from 0.5 × FLC to 11.0 × FLC. The alarm relay will activate immediately when the
average three phase current exceeds this setpoint value when the motor is running.
This feature can also operate during start condition using the
setpoint described below.
• INHIBIT ON START FOR: If all other conditions are met for an immediate overload
alarm to occur and the motor is starting, the alarm will occur when the delay set in
this setpoint has elapsed. If this setpoint is set to
alarm will never occur during a start.
• MECHANICAL JAM FUNCTION: In protecting driven equipment such as pumps,
gearboxes, compressors and saws, it is often desirable to have an immediate trip in
the event of a locked rotor during running. During startup the mechanical jam can be
disabled using the
INHIBIT ON START FOR
inrush of 600% is normal. Use of this feature with loads that experience overloads as
part of normal operation such as crushers is not recommended.
• MECHANICAL JAM PICKUP: If a fast trip for mechanical jam is required, enable the
feature and enter the average current pickup value above the normal maximum
expected operating average phase current.
• MECHANICAL JAM DELAY: If the average phase current exceeds the
setpoint value when the motor is running, and remains this way for the
JAM PICKUP
time delay programmed, one of the assigned relay(s) will activate. Since the
mechanical jam function can be assigned to any relay, if
AUX RELAYS are assigned, the function is considered to be a trip and the "CAUSE OF
LAST TRIP: MECHANICAL JAM" message will be displayed. Conversely, if the function is
assigned to ALARM, and the above conditions are met, the fault is considered to be an
ALARM, and the 239 will display "MECHANICAL JAM ALARM".
CHAPTER 4: PROGRAMMING
S4: PROTECTION\PHASE CURRENT\PHASE S/
INHIBIT ON START FOR
, the immediate overload
UNLIMITED
setpoint described below, since a typical
,
TRIP AUXILIARY
239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
the 239
INST
MECHANICAL
, or
TRIP &