ABB RELION REX640 Technical Manual page 432

Protection and control

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Protection functions

and long-time thermal history, allowing more critical situations like motor start-ups

to be taken into consideration more carefully.

Setting of thermal restart level

For instance, if the start-up time of the motor is 4 seconds, and the calculated

operate time of the thermal protection stage for cold motor is 6 seconds, one

motor start-up will use 4/6 = 66.6% of the thermal capacity of the motor. Therefore,

(100% - (66.6% + margin), where margin is 5%).

Setting of thermal alarm level

Tripping due to high overload can be avoided by reducing the load of the motor

when the thermal level reaches a set alarm level.

full thermal capacity without causing a trip due to long time overload. Generally, the

Alarm thermal value is set to 80....90% of the trip level.

RPTTR Input signals

Table 488: RPTTR Input signals

Restart thermal Val can be calculated as follows:

Restart thermal Val must be set to below 100% - 66.6% = 33.3% say to 28.3%

Alarm thermal value can be set to a level, which will allow the use of the motor's

1MRS759142 F

(Equation 55)

Three-phase currents

Three-phase voltages

Block signal for acti-

vating the blocking

Signal for indicating

the need for emer-

The ambient temper-

ature used in the cal-

Technical Manual