Phase Ct And Motor Full Load Current Setpoints; Acceleration Time Setpoint; Number Of Starts/Hour Setpoint - GE 169 Instruction Manual

g
GE Power Management
3 SETUP AND USE

3.7 Phase CT and Motor Full Load Current Setpoints

The "PHASE CT RATIO" is entered into the 169 relay in SETPOINTS mode, page 1. This value must be entered
correctly in order for the relay to read the actual motor phase currents (this setpoint should be in a range from 50%
to 95% of FLC).
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, this should be multiplied by the nameplate full load current and the result entered
into the 169 as the motor full load current.
When the relay detects a current greater than the full load current, the time/overload curve will come into effect, and
the Trip relay will activate 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 169 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 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 169 when an average phase current
greater than one full load current is detected following a motor stop condition. A normal running condition will be
detected by the relay when the phase current drops to below one full load current for any length of time following a
start. When the phase current drops to below 5% of CT primary rated amps a motor stop will be detected.
To protect against a locked rotor condition the 169 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 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 Acceleration Time function is not required the setpoint should be set to "OFF".

3.9 Number of Starts/Hour Setpoint

The allowable number of motor starts per hour is entered into the 169 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 activation
when this value is equal to the setpoint value. A trip will occur only after the motor is stopped. This setpoint should
be obtained from the motor manufacturer's data sheets. If more than 5 starts/hour are allowed this setpoint should
be stored as "OFF". The relay starts/hour counter will be saved if power is lost to the unit. Note that the 169 relay
must detect all motor start attempts (see section 3.8) in order for this function to operate correctly.
The "ENABLE AUTO-RESET OF START TRIPS?" setpoint, when enabled, will automatically reset a STARTS/HOUR
trip once the lockout time has elapsed.
61