ABB RELION 611 Series Technical Manual page 297

1MRS757454 D
611 series
Technical Manual
below 90 percent of the set value of Start detection A and remain below that level for
a time of Str over delay time, that is, until the start-up situation is over.
GUID-4475BDFB-57AE-4BFD-9EE7-AE7672F7206E V2 EN
Figure 136: Functionality of start-up supervision in the "IIt and IIt&stall" mode
In case of the "IIt, CB" or "IIt & stall, CB" modes, the function initially recognizes the
de-energized condition of the motor when the value of all three phase currents is below
the value of the Motor standstill A setting for 100 milliseconds. The beginning of the
motor start-up is recognized when CB is closed, that is, when the CB_CLOSED input
is activated and at least one phase current value exceeds the Motor standstill A setting.
These two events do not take place at the same instant, that is, the CB main contact is
closed first, in which case the phase current value rises above 0.1 pu and after some
delay the CB auxiliary contact gives the information of the CB_CLOSED input. In
some cases, the CB_CLOSED input can be active but the value of current may not be
greater than the value of the Motor standstill A setting. To allow both possibilities, a
time slot of 200 milliseconds is provided for current and the CB_CLOSED input. If
both events occur during this time, the motor start-up is recognized.
The motor start-up ends either within the value of the Str over delay time setting from
the beginning of the start-up or the opening of CB or when the CB_CLOSED input is
deactivated. The operation of the MOT_START output signal in this operation mode
is as illustrated in Figure
This CB mode can be used in soft-started or slip ring motors for protection against a
large starting current, that is, a problem in starting and so on.
137.
Section 4
Protection functions
291