ABB REM 610 Technical Reference Manual page 24

REM 610
24
Motor Protection Relay
Technical Reference Manual
The reduced ability of the motor to cool down during standstill is taken into account
by setting the cooling time constant to be longer than the heating time constant. The
time constant multiplier, K
constant and determines the cooling rate of the motor at standstill.
At power up, the thermal level will be set to approximately 70 per cent of the thermal
capacity of the motor. This will ensure that the stage will trip within a safe time span.
Under a low-load condition, the calculated thermal level will slowly approach the
thermal level of the motor.
Note!
At a low prior alarm level, connecting the auxiliary supply to the relay will cause a
thermal alarm due to the initialization of the thermal level to 70 per cent. The thermal
level can be reset via the HMI during power up.
Note!
The thermal level can be reset or changed via serial communication, which will
generate an event code.
Note!
On the rising edge of the emergency start signal the thermal level will be set below
the thermal restart inhibit level. This will allow at least one motor start up even
though the thermal level has exceeded the restart inhibit level.
Note!
When stage θ> starts during motor start up, neither a start signal nor an event code
will be generated.
, is the ratio of the cooling time and the heating time
c
1MRS 752263-MUM