Choosing the Right Unipower Load Monitor

🔍 Why Load Monitoring Requires True Motor Power (kW)

Electrical engineers already understand the limitations of current-only protection. A motor’s current does not always correlate to its mechanical load, especially when driven by a VFD. This is why Unipower products measure true motor power (kW), not just current or power factor.

Real power (kW) directly represents the torque being delivered at the shaft. Because mechanical loading is reflected immediately in true power, Unipower devices can detect:

• Underload (dry running pumps, burst pipes, broken couplings)
• Overload (blocked impellers, jammed conveyors, mechanical seizure)
• Process deviations (loss of media, product starvation, belt slip)

This relationship between mechanical load and real power makes kW the most reliable parameter for machinery protection and process monitoring.

Explore the full Unipower range: Unipower at Charter Controls.

⚡ HPL110 — Practical, Reliable Load Protection

The HPL110 is the compact, cost-effective choice for installers and OEMs needing straightforward load protection with minimal setup time. It uses true power measurement but maintains simple dial-based configuration for rapid commissioning.

• Underload and overload trip protection
• Excellent for fixed-speed pumps and light conveyors
• Fast dial-based setup (no menus)
• DIN-rail mounting
• Stable operation even with supply variations

View HPL110 →

🚀 HPL500 — Advanced Digital Load Monitoring and Protection

The HPL500 is the flagship Unipower model for industrial applications where precise load behaviour matters. Its digital processing, filtering algorithms and configurable logic make it suitable for demanding machinery, including systems driven by modern VFDs.

• Digital display with button-based programming
• High-accuracy kW measurement with active filtering
• Multiple trip functions (underload, overload, load window)
• Two fully programmable relays
• Optimised for both DOL and VFD operation

View HPL500 →

HPL500MB — Adds Modbus RTU for SCADA and PLC Connectivity

The HPL500MB includes all of the capabilities of the HPL500 and adds Modbus RTU communication. This option enables remote visibility, data acquisition and integration into control systems without additional transducers.

• Modbus RTU for PLC / SCADA / telemetry
• Read real-time kW, load %, status and alarms
• Remote parameter configuration
• Ideal for water utilities, OEMs and remote pump stations

View HPL500MB →

📊 HPL503 — 4–20 mA / 0–10 V Load Transducer

The HPL503 converts true motor load into a standard process signal for PLC analog inputs. It is ideal when the control system handles logic, alarms and scaling.

• 4–20 mA or 0–10 V output proportional to kW
• No internal trip relays — measurement only
• Compatible with VFDs and fixed-speed motors
• Excellent for trending and process optimisation

View HPL503 →

🧰 HPL500H — Handheld Programmer

The HPL500H enables quick upload and download of configuration parameters for HPL500-series monitors. This is especially useful for OEMs producing multiple identical panels.

• Duplicate parameter sets instantly
• Speed up commissioning and servicing
• Minimise configuration errors

View HPL500H →

🔌 Integration into Modern Control Panels and PLC Systems

All Unipower products are designed for seamless panel integration:

• Wide power measurement range for pumps, conveyors and industrial machines
• DIN-rail mounting
• Relay outputs for alarms and trips (except HPL503)
• Analogue outputs on the HPL503
• Modbus RTU available on the HPL500MB
• Stable, accurate operation on VFD-driven systems

For application advice, contact the Charter Controls engineering team:
Contact Charter Controls.

❓ Frequently Asked Questions

Why does Unipower measure true power instead of current?

True power (kW) directly reflects mechanical load and torque. Current alone does not reliably indicate mechanical conditions, especially on VFDs where current can fluctuate independently of the load.

Which model should I use for pump dry-run protection?

The HPL110 offers simple, reliable dry-run detection. For heavier industrial pumps or applications requiring advanced filtering, the HPL500 is recommended.

Which model supports Modbus?

The HPL500MB adds Modbus RTU communication for SCADA and PLC systems.

Which model provides an analogue output?

The HPL503 provides either 4–20 mA or 0–10 V output proportional to true motor load.

Can these devices be used with VFDs?

Yes. All Unipower models use kW-based measurement, which remains accurate on variable frequency drives.

Where can I purchase Unipower products?

All models are available directly from Charter Controls:
Unipower Brand Page.