at desired values. This is accomplished through the use of the
indicators described above.
To set a trip parameter at a predetermined value, an internally
simulated calibration current is set at the desired value
through the use of a potentiometer and the panel meter and is
used as an input for the relay. The trip parameter is then set
by adjusting a potentiometer until the indicator (LED) for
the trip parameter barely activates.
The desired time-inverse characteristic is selected by: 1) setting
the desired pickup current value, 2) adjusting the internal
calibration current to a level above the pickup value where the
desired time required for time-out is known, and 3) then
resetting the time-out device and measuring the time to trip.
A potentiometer permits a continuous control of this time.
A pulse is generated in the relay that begins when the time
integration starts and ends when the relay has timed out.
This signal is available on the panel of the relay and can be
timed using an oscilloscope or a digital timer.