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Motor Management and Control Devices, or Overloads protect Motors 
............but what’s protecting your machine? 
The HPL500 is used to protect motor driven machines from the damage that can occur when a 
motor drives against a jam or blockage or continues to run during abnormal operating conditions. 
It achieves this without any sensors or remote wiring and is therefore totally non-intrusive. 
The HPL500 measures; 
Motor kW and displays actual kW or kW% of scaled range 
Motor Input Power or Shaft Output Power 
Current up to 40A direct (27.7kW @ 400v) via feed through tube (>40A use n:5 CT) 
Motor Voltage of 3 x 100-575Vac and 1 x 100-400Vac (Power supply patented PR177225) 
The HPL500 features; 
Scalable Analogue o/p proportional to measured kW 0(4)-20mA 
Input to select active limit for 2 speed motor applications 
Peak detector memories to simplify setting accurate trip points 
2 freely configurable output relays (Min/Max, Min/Min, Max/Max) 
Individual Trip Delay Timers for both relays, 0 - 999 seconds 
Start-up surge masking timer, 0 - 999 seconds 
Modbus RTU comms’ & hand-held programmer options 
Protect Pumps from dry running and cavitation, protect Screens, Scraper Bridges, Crushers, Screw 
and Belt Conveyors and Penstocks from jams or overloading, Monitor Fans for broken belt or shut 
damper. Use analogue signal for PLC/SCADA input, closed loop control and End Point Monitoring 
Unipower HPL Digital Load Monitors have been used in industrial motor driven applications for over 20 
years. They are extensively used in Water and Waste, Pharmaceutical, Petro-Chemical, Agro-Chemical 
and many other industrial applications for the protection of machines from damage caused by the motor 
when a machine fault or abnormal load situation occurs. It is not possible to use motor current for this 
purpose as current is not proportional to load. Motor Overloads, either thermal or electronic, are not 
designed to measure instantaneous increases or decreases in load and damage will occur before they 
can react. 
 
 
The HPL500 represents the latest generation of 
the Unipower range. Its enhanced features enable 
it to replace 5 models in the previous range. In 
addition it can operate on a wide motor voltage 
range of 100 - 400Vac single phase and 100 - 
575Vac three-phase at 50 & 60Hz using a unique 
power supply for which a patent is pending. The 
HPL500 also measures current up to 40 amps via 
its feed through tube (That’s 27.7kW @ 400v), and 
without limit if a current transformer is used. 
 
Programming the HPL500s’ over and under load 
trip points is simple. Using only three push buttons, 
it features Peak Detectors which capture and 
store the minimum and maximum power. Refer- 
ence to these detectors will guide you to set the 
trip levels quickly and accurately. Either limit can 
be turned off and the two output relays can be 
independently configured as either Over or Under 
Load alarms. Therefore you can select an Under 
and Over Load alarm, two Over Load alarms (pre 
alarm and Alarm) or two Under Load alarms. 
 
Other features include; 
Tr Reaction Timers, for each limit, both independ- 
ently adjustable from 0-999 seconds. 
Ts Start-up surge timer. Triggered by the meas- 
ured power exceeding the 5% threshold (see Fig. 
1), the start-up surge timer masks the motor start 
inrush. As it is triggered by the 5% threshold, not 
power on, the HPL500 can be connected either 
before or after the motor contactor. 
Adjustable from 0-999 seconds. 
 
Alarm Reset, either by the reset button on the 
front plate or a reset contact on the S1 input. 
Auto-reset can be programmed if required 
S2 input, 2 selectable modes; 
1) Alarm inhibit, Prevents an alarm at any time 
when the power goes outside the limits for normal 
operational reasons, e.g. speed ramp up/down, 
pump flush etc. 
2) Select active limit for 2 speed motor applications 
 
Auto shut-down inhibits an under-load alarm 
when the motor is switched off intentionally. 
 
Hysteresis is used to program a differential be- 
tween a trip point and its reset point. (Auto-reset 
only) Each limit has independent hysteresis levels. 
 
Analogue output 0-(4)-20mA for SCADA/PLC 
input which can be scaled (Zoom function) so 
that the measured power range uses the entire 
analogue output range. 
 
Filtering of the measured power signal by pro- 
gramming a time constant on noisy supplies. 
 
Display can be set to show kW or kW% 
 
Motor input power P1 is the default measurement 
principle however in some applications it can be 
advantageous to measure Shaft Output Power P2
The HPL500 features a unique motor loss P0 
calculation principle which closely follows motor 
losses throughout the full power range. This is 
then subtracted from the input power; 
P2 = P1 - P0 
 
Options: 
Modbus RTU Communications 
HPL500-H Hand Held programmer (Modbus only) 
Tagged as: Unipower
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