Inhibits - GE 269Plus Instruction Manual

INHIBITS

An Inhibit is a feature that becomes active only once a motor STOP condition has been detected and prevents
motor starting until the Inhibit has timed out. There are four Inhibit features in the 269Plus. They are
,
H O U R T I M E B E T W E E N S T A R T S
relays in one group as Inhibits. After a motor has stopped, if any of the Inhibits are active, the output relay(s)
assigned to Inhibits will activate and the message that appears will represent the Inhibit with the longest lock-
out time remaining. Neither of the Inhibits will increment any of the statistical values of page four of actual val-
ues, and all of the Inhibits are always auto-reset, unless they are assigned to AUX1 and the Special External
Reset function in Setpoints page 5 is enabled (see Sections 2.13 and 3.24 for details).
The allowable number of motor Starts per Hour is entered in Setpoints page 1. The relay keeps a record of the
number of motor starts over the past hour and causes an output relay activation when this value is equal to the
3
setpoint value. An Inhibit will occur only after the motor is stopped. This setpoint value should be obtained from
the motor manufacturer's data sheets. If more than 5 starts/hour are allowed, this setpoints should be stored as
. The relay starts/hour counter will be saved if power is lost to the unit. Note that the relay must detect all
O F F
motor start attempts (see Section 3.9: ACCELERATION TIME SETPOINT above) in order for this feature to
operate correctly.
A value in minutes for the
starts timer is loaded during a start condition and begins to decrement (Actual Values page 1, line 7). Once the
motor stops, if the timer has not decremented to zero, an Inhibit will occur. The Inhibit will time out when the
timer decrements to zero, and another start will be possible. The
Section 3.22.
A value in minutes for the
while the rotor continues to rotate. In the case of a pump motor, the rotor may actually spin backwards when
the pump is stopped, creating a very hazardous condition for a motor start. If this setpoint is enabled, the timer
is loaded once the motor starts and the inhibit becomes active. The inhibit will time out when the Backspin
Timer is zero and another start will be possible.
It is recommended that a very liberal time be set for the BACKSPIN TIMER as it is only a timer
and cannot sense motor rotation!
WARNING
Due to the nature of the Inhibit features, they fall into the class of 269Plus Trip features and
therefore they must be active only during a motor 'STOP' condition (ONLY ONE TRIP OR
INHIBIT MAY OCCUR AT ANY ONE TIME). The detection of a motor 'STOP' condition is impor-
NOTE
tant. In the case where a motor may idle at less than 5% of rated CT primary amps (i.e. syn-
chronous motors), it is imperative that a 52B contact is input to the spare terminals (44, 45) to
detect a motor 'STOP' condition (52B contact reflects the opposite state of the breaker).
Enabling the 52B contact setpoint in page 5 of setpoints will allow the 269Plus to determine a
'STOP' condition if motor current is less than 5% CT primary and the 52B contact is closed.
It is recommended that the trip functions and inhibit features be assigned to different relays. For example, all
the trip functions may be assigned to activate the TRIP relay when a trip condition is met. The Inhibit Lockout
should then be assigned to activate the AUX1 relay when the motor stops and an inhibit is issued by the
269Plus. Separating TRIPs and INHIBITs in this manner makes it easier for operators to properly diagnose
problems and take appropriate corrective action.
Also, the
C A U S E O F L A S T E V E N T
was a TRIP or an INHIBIT.
Inhibit lockouts are assigned to the AUX1 relay as a factory default. Ensure that AUX1 contac-
tors are properly wired in your control circuit. See Figures 3–2: WIRING DIAGRAM FOR CON-
TACTORS and 3–3: WIRING DIAGRAM FOR BREAKERS on pages 3–51 for wiring details.
NOTE
3-
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, , and
S T A R T I N H I B I T B A C K S P I N T I M E R
feature is entered in Setpoints page 5. The time between
T I M E B E T W E E N S T A R T S
is entered in Setpoints page 5. This timer prevents motor starts
B A C K S P I N T I M E R
message seen on Actual Values page 5 clearly shows whether the last event
269Plus Motor Management Relay
3 SETUP AND USE
. These four features are assigned to output
feature is explained in detail in
S T A R T I N H I B I T
GE Power Management
3.10 INHIBITS
S T A R T S /