Application; Signals - ABB RED615 Technical Manual

Section 4
Protection functions
4.1.7.5
4.1.7.6
242
Blocking logic
There are three operation modes in the blocking functionality. The operation modes
are controlled by the BLOCK input and the global setting "Configuration/System/
Blocking mode" which selects the blocking mode. The BLOCK input can be
controlled by a binary input, a horizontal communication input or an internal signal
of the IED program. The influence of the BLOCK signal activation is preselected
with the global setting Blocking mode.
The Blocking mode setting has three blocking methods. In the "Freeze timers"
mode, the operation timer is frozen to the prevailing value. In the "Block all"
mode, the whole function is blocked and the timers are reset. In the "Block
OPERATE output" mode, the function operates normally but the OPERATE output
is not activated.

Application

The motor protection during stall is primarily needed to protect the motor from
excessive temperature rise, as the motor draws large currents during the stall phase.
This condition causes a temperature rise in the stator windings. Due to reduced
speed, the temperature also rises in the rotor. The rotor temperature rise is more
critical when the motor stops.
The physical and dielectric insulations of the system deteriorate with age and the
deterioration is accelerated by the temperature increase. Insulation life is related to
the time interval during which the insulation is maintained at a given temperature.
An induction motor stalls when the load torque value exceeds the breakdown
torque value, causing the speed to decrease to zero or to some stable operating
point well below the rated speed. This occurs, for example, when the applied shaft
load is suddenly increased and is greater than the producing motor torque due to
the bearing failures. This condition develops a motor current almost equal to the
value of the locked-rotor current.
JAMPTOC is designed to protect the motor in stall or mechanical jam situations
during the running state. To provide a good and reliable protection for motors in a
stall situation, the temperature effects on the motor have to be kept within the
allowed limits.

Signals

Table 245: JAMPTOC Input signals
Name Type
I_A SIGNAL
I_B SIGNAL
I_C SIGNAL
BLOCK BOOLEAN
Default Description
0 Phase A current
0 Phase B current
0 Phase C current
0=False Block signal for activating the blocking mode
1YHT530004D05 D
615 series
Technical Manual