Unipower HPL500 Advanced Digital Motor Load (kW) Monitor
Posted on 14th October 2024
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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