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3 SETUP AND USE
The
is entered in Setpoints page 1. This value must be entered correctly for the relay to read
P H A S E C T R A T I O
the actual motor phase currents. The choice of phase CTs depends on the motor Full Load Current. 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 motor FLC should be equal to the phase CT primary, but never more (see Sections
2.1: PHYSICAL DIMENSIONS and 2.5: PHASE CT INPUTS). The maximum phase CT primary current is 1500
A. For higher ratings, please contact GE Power Management.
The
M O T O R F U L L L O A D C U R R E N T
overheating and should be taken from the motor nameplate or data sheets. It is entered in Setpoints page 1.
If the motor has a service factor, it may be accommodated using the
tions 3.20 and 3.22 for additional information.
When the relay detects a current greater than the
comes into effect and the Trip relay activates 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.
The acceleration time of the drive system is entered in Setpoints page 1. This feature is strictly a timer that can
be used to protect the equipment driven by the motor. This time does not affect the thermal memory calculated
by the relay.
The acceleration time is used by the relay as the maximum allowable time between a motor start attempt and
the beginning of normal running operation. A motor start attempt is detected by the 269Plus 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 overload 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 (i.e. synchronous motor) it is imperative that a 52b contact is input to the 269Plus (52b contact reflects
the opposite state of the breaker). The 269Plus will then determine a "STOP" condition if motor current is less
than 5% of CT primary and the 52b contact is closed (see Section 3.10: INHIBITS).
To protect against a locked rotor condition the 269Plus relay allows its thermal memory (see Section 3.22:
THERMAL MEMORY on page 3–59) to fill during a start. Thus if the heat produced by a locked rotor condition
causes the thermal capacity of the motor 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
function is not required, the setpoint should be set to
A C C E L . T I M E
GE Power Management
Courtesy of NationalSwitchgear.com
PHASE CT & MOTOR FULL LOAD CURRENT SETPOINTS
3.8 PHASE CT & MOTOR FULL LOAD CURRENT SETPOINTS
is used as the maximum continuous current that the motor can draw without
O V E R L O A D P I C K U P L E V E L
269Plus Motor Management Relay
setpoint; see Sec-
O V E R L O A D P I C K U P L E V E L
× FLC, the time/overload curve
3.9 ACCELERATION TIME SETPOINT
.
O F F
3
3-
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