θ
i
startup time of the motor
operate time when no prior load
=
−
×
100
10
%
0
0%
+
margin
GUID-5B3B714D-8C58-4C5D-910D-A23852BC8B15 V2 EN
(Equation 22)
For example, the motor start-up time is 11 seconds, start-up current 6 x rated and
Time
constant start
is set for 800 seconds. Using the trip curve with no prior load, the operation
time at 6 x rated current is 25 seconds, one motor start-up uses 11/25 ≈ 45 percent of the
thermal capacity of the motor. Therefore, the restart disable level must be set to below 100
percent - 45 percent = 55 percent, for example to 50 percent (100 percent - (45 p
margin), where margin is 5 percent).
Setting the thermal alarm level
Tripping due to high overload is avoided by reducing the load of the motor on a prior
alarm.
The value of
Alarm thermal value
is set to a level which allows the use of the full thermal
capacity of the motor without causing a trip due to a long overload time. Generally, the
prior alarm level is set to a value of 80 to 90 percent of the trip level.
4.1.9.6
Signals
Table 310:
49M Input signals
Name
Type
Default
Description
I_A
SIGNAL
0
Phase A current
I_B
SIGNAL
0
Phase B current
I_C
SIGNAL
0
Phase C current
I
2
SIGNAL
0
Negative sequence current
BLOCK
BOOLEAN
0=False
Block signal for activating the blocking mode
START_EMERG
BOOLEAN
0=False
Signal for indicating the need for emergency start
AMB_TEMP
FLOAT32
0
The ambient temperature used in the calculation
Table 311:
49M Output signals
Name
Type
Description
TRIP
BOOLEAN
Trip
ALARM
BOOLEAN
Thermal Alarm
BLK_RESTART
BOOLEAN
Thermal overload indicator, to inhibit restart
1MAC059074-MB A
Section 4
Protection functions
615 series ANSI
311
Technical Manual
Summary of Contents for Relion 615 series
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