GE 469 Instruction Manual page 90

4.6 S5 THERMAL MODEL
100
75
50
25
0
0
4
100
75
50
25
0
0
f) HOT/COLD CURVE RATIO
The motor manufacturer may provide thermal limit information for a hot/cold motor. The 469 thermal model adapts for these
conditions if the
HOT/COLD CURVE RATIO
used the relay will settle at for current levels below the
is below the
OVERLOAD PICKUP LEVEL
phase current and the
per minute or fall as dictated by the running cool time constant.
where: TC =
used_end
I = equivalent motor heating current
eq
hot / cold =
HOT/COLD CURVE RATIO
The
HOT/COLD CURVE RATIO
Simply divide the hot safe stall time by the cold safe stall time. If hot and cold times are not provided, there can be no differ-
entiation and the
HOT/COLD CURVE RATIO
4-40
Courtesy of NationalSwitchgear.com
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Ieq/Overload Pickup= 80%
30 60 90 120 150
Time in Minutes
80% LOAD
Cool Time Constant= 30 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Motor Stopped after running Rated Load
TCused_end= 0%
30 60 90 120 150
Time in Minutes
MOTOR STOPPED
Figure 4–13: THERMAL MODEL COOLING
setpoint is programmed. This setpoint value dictates the level of thermal capacity
, the
THERMAL CAPACITY USED
setpoint. The
HOT/COLD CURVE RATIO
TC
=
used_end
if I
THERMAL CAPACITY USED
per_unit
setpoint
may be determined from the thermal limit curves if provided or the hot and cold safe stall times.
should be entered as "1.00".
469 Motor Management Relay
100
75
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
50
Ieq/Overload Pickup= 100%
25
0
180
0 30
100
75
Cool Time Constant= 30 min
TCused_start= 100%
Hot/Cold Ratio= 80%
Motor Stopped after Overload Trip
50
TCused_end= 0%
25
0
180 0 30
MOTOR TRIPPED
. When the motor is running at a level that
OVERLOAD PICKUP LEVEL
register will rise or fall to a value based on the average
THERMAL CAPACITY USED
 
hot
× ×
I 1 100%
– ---------- -
 
eq
cold
remains steady state
4 SETPOINTS
60 90 120 150 180
Time in Minutes
100% LOAD
60 90 120 150 180
Time in Minutes
808705A1.CDR
will either rise at a fixed rate of 5%
(EQ 4.7)
GE Multilin