4.5.4.2 Function block
Figure 340: Function block
4.5.4.3 Functionality
The single-phase undervoltage protection function PHAPTUV is used to disconnect
damaged devices from the network. These can be, for example, electric motors
which are damaged when subjected to service under low voltage conditions.
The function contains a blocking functionality. It is possible to block function
outputs, timers or the function itself, if desired.
4.5.4.4 Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "On" and "Off".
The operation of PHAPTUV can be described using a module diagram. All the
modules in the diagram are explained in the next sections.
Figure 341: Functional module diagram
Level detector
The fundamental frequency component of the measured single-phase voltage is
compared phase-wise to the set value of the
Start value
setting. If the measured
value is lower than the set value of the
Start value
setting, the Llevel detector
activates the Timer module. The
Relative hysteresis
setting can be used for
preventing unnecessary oscillations if the input signal slightly varies above or below
the
Start value
setting. After leaving the hysteresis area, the start condition has
to be fulfilled again and it is not sufficient for the signal to only return to the
hysteresis area.
The
Voltage selection
setting is used for selecting phase-to-earth or phase-to-
phase voltages for protection.
For the voltage IDMT operation mode, the used IDMT curve equations contain
discontinuity characteristics. The
Curve Sat relative
setting is used for preventing
unwanted operation.
Protection functions
1MRS757644 H
654 620 series
Technical Manual
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