Functional Description
The Unipower HPL110A may be used either for monitoring applications - to protect
process equipment - or for control applications - to control secondary process functions.
Monitoring Example for Machinery Protection
A typical Power vs. Time graph for the HPL110A is shown in Figure 2.1 with the Y-axis
showing power P in units of %kW and the X-axis showing time.
At time 0, mains power is turned on, the HPL110A unit is energized and the alarm
relay changes state to the “on” condition.
At time 1, the motor is turned on and the load immediately surges due to the starting
current inrush before settling to a steady value at time 4.5.
At time 8, this example shows power rising above the L1 Max. Limit which triggers an
alarm resulting in the motor being switched off at time 9.5.
A continuation is shown starting at time 20 where the motor load drops such that it
falls below the L2 Min Limit at time 22. An alarm is again triggered after the delay
timer expires resulting in the motor again being shut down at time 23.
0%
Max. Limit
L1
100%
P (%)
Ts
t
Tr1
Power On
Relay On
5%
Motor On
0 1 2 3 4 5 6 7 8 9 2 0 2 1 2 2 2 3
P = f (t)
Min. Limit
L2
Tr2
4
2
F i g u re 2 . 1
