Setting the thermal restart level
The restart disable level can be calculated as follows:
θ
i
startup time of the motor
operatetime when no prior load
= − ×100 10% 00% +
margin
GUID-5B3B714D-8C58-4C5D-910D-A23852BC8B15 V1 EN (Equation 14)
For example, the motor startup 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 startup 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 percent + 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 258: MPTTR 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
TEMP_AMB FLOAT32 0 The ambient temperature used in the calculation
Table 259: MPTTR Output signals
Name
Type Description
OPERATE BOOLEAN Operate
ALARM BOOLEAN Thermal Alarm
BLK_RESTART BOOLEAN Thermal overload indicator, to inhibit restart
Section 4 1YHT530004D05 D
Protection functions
260 615 series
Technical Manual
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