GE MULTILIN 269 MOTOR MANAGEMENT RELAY Series Instruction Manual Download

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3 SETUP AND USE

3-44

3.7 Phase CT and Motor Full Load Cur-
rent Setpoints

The "PHASE CT RATIO" is entered into the 269 relay in
SETPOINTS mode, page 1. This value must be en-
tered correctly in order for the relay to read the actual
motor phase currents. The choice of phase CTs de-
pends on the Full Load Current of the motor. The
Phase CTs should be chosen such that the Full Load
Current is not less than 50% of the rated phase CT
primary. For maximum accuracy, the phase CT primary
should be equal to the FLC of the motor, but never
more. The maximum phase CT primary current is
1500A. For higher ratings, please contact the factory.

The "MOTOR FULL LOAD CURRENT" setpoint is used
by the relay as the maximum continuous current that
the motor can draw without overheating and should be
taken from the motor nameplate or data sheets. It is
entered into the relay in SETPOINTS mode, page 1.

If the motor has a service factor, it may be accommo-
dated using the Overload Pickup Level setpoint. See
Sections 3.18 and 3.20.

When the relay detects a current greater than the
Overload Pickup Level x FLC, the time/overload
curve will come into effect, and the Trip relay will acti-
vate after a time determined by the overload curve
shape, the amount of phase current unbalance present
and the RTD bias (when enabled), and the thermal
memory contents.

3.8 Acceleration Time Setpoint

The acceleration time of the drive system is entered
into the 269 relay in SETPOINTS mode, page 1. This
feature is strictly a timer that can be used to protect the
equipment driven by the motor. This time does not af-
fect the thermal memory calculated by the relay.

The acceleration time is used by the relay as the
maximum allowable time between a motor start at-
tempt and the beginning of normal running operation. A
motor start attempt is detected by the 269 when an
average phase current greater than one full load current
is detected within one second following a motor stop
condition. A normal running condition will be detected
by the relay when the phase current drops below over-
load pickup

FLC for any length of time following a start.

When the phase current drops below 5% of CT primary
rated amps a motor stop will be detected. In the case
where a motor may idle at less than 5% of rated CT
primary Amps (ie. synchronous motor) it is imperative
that a 52b contact is input to the 269 (52b contact re-
flects the opposite state of the breaker). The 269 will
then determine a “STOP” condition if motor current is
less than 5% of CT primary and the 52b contact is
closed (see section 3.9).

To protect against a locked rotor condition the 269 relay
allows its thermal memory (see section 3.20) to fill
during a start. Thus if the heat produced by a locked
rotor condition causes the thermal capacity of the mo-
tor to be exceeded, an overload trip will be initiated.
The acceleration time setpoint can only be used for
driven load protection, not locked rotor protection.

If the Acceleration Time function is not required, the
setpoint should be set to "OFF".

3.9 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
two Inhibit features in the 269. They are Starts/Hour
and Time Between Starts. These two features are as-
signed to output relays in one group as Inhibits. After a
motor has stopped, if either 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 lockout time remaining. Neither of the In-
hibits will increment any of the statistical values of page
four of actual values, and all of the Inhibits are always
auto-reset.

The allowable number of motor Starts per Hour is en-
tered into the 269 relay in SETPOINTS mode, page 1.
The relay keeps a record of the number of motor starts
over the past hour and will cause an output relay acti-
vation when this value is equal to the setpoint value. An
Inhibit will occur only after the motor is stopped. This
setpoint should be obtained from the motor manufac-
turer's data sheets. If more than 5 starts/hour are al-
lowed, this setpoints should be stored as "OFF". The
relay starts/hour counter will be saved if power is lost to
the unit. Note that the 269 relay must detect all motor
start attempts (see section 3.8) in order for this feature
to operate correctly.

A value in minutes for the Time Between Starts feature
is entered into the 269 relay in setpoints mode, page 5.
The time between starts timer is loaded during a start
condition and begins to decrement. Once the motor
stops, if the timer has not decremented to zero, an In-
hibit will occur. The Inhibit will time out when the timer
decrements to zero, and another start will be possible.

NOTE: Due to the nature of the Inhibit features,
they fall into the class of 269 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 important. In the case
where a motor may idle at less than 5% of rated CT
primary amps (i.e. synchronous motors), it is im-
perative 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