Unipower HPL500 vs Emotron M20: The Superior Motor Load Monitor
Unipower HPL500 vs Emotron M20: The Superior Motor Load Monitor
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Summary: For most UK control panel and machinery protection applications, the
Unipower HPL500 offers better value, easier installation, and broader voltage coverage
than the Emotron M20 (RS 6550141). The HPL500 integrates 40 A feed-through current
measurement and a universal 100–575 V AC supply, reducing total installed cost while providing advanced
configuration and control.
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UK Pricing Snapshot (as of 11th November 2025)
Beyond the Basics: Why the Unipower HPL500 Is the Superior Choice for Motor Load Monitoring
In industrial automation and control panel design, protecting capital-intensive machinery is paramount.
Motor load monitors provide essential protection for pumps, conveyors, crushers, and mixers — detecting
dry running, cavitation, jams, and tool breakage by measuring the motor’s true power (kW). This is far more
reliable than simple current-based relays.
Two respected DIN-rail-mounted options dominate this space: the Emotron M20 and the
Unipower HPL500. Both are proven, high-quality shaft power monitors — but a closer technical
comparison shows that the Unipower HPL500 is decisively the better investment for panel builders
and engineers. It offers broader application range, lower total cost, and more advanced diagnostic control.
1. Total Cost of Ownership: An Installation-First Perspective
While upfront unit price matters, the total installed cost is what truly counts. Here, the HPL500
takes a commanding lead.
- Unipower HPL500 (RS: 745-8030): Integrated feed-through current measurement up to 40 A (roughly 22 kW at 400 V).
- Emotron M20 (RS: 655-0141): Requires an external current transformer (CT) for every application.
The M20’s reliance on a CT creates extra costs in three ways:
- Component Cost: The CT must be purchased separately.
- Panel Space: The CT occupies additional DIN-rail or mounting space.
- Labour Cost: Wiring complexity increases as motor cables must be routed through the CT.
The HPL500 avoids all three up to 40 A, covering the majority of typical UK motor applications.
With a list price already ~15% lower than the M20 (£526.66 vs £619.99), and no CT required, the Unipower HPL500's
true installed cost is dramatically lower.
2. Unmatched Application Flexibility and Stocking Simplicity
The HPL500 simplifies specification, procurement, and inventory management. Its patented
universal power supply means a single unit covers both 1-phase 100–400 V AC and
3-phase 100–575 V AC. That is one SKU for virtually any industrial supply worldwide — 230 V,
400 V, 480 V, 575 V — ideal for OEMs exporting globally.
By contrast, the Emotron M20 is produced in voltage-specific variants. The RS 655-0141 model
handles 380–500 V AC only. To serve other voltages, an engineer must specify and stock separate models.
This complicates procurement, increases inventory, and introduces potential ordering errors — issues the
HPL500 completely avoids.
3. Advanced, Data-Driven Control for Engineers
Both monitors measure motor load, but their approach to control setup differs. While the M20’s Auto-Set is
convenient for simple commissioning, the HPL500 is engineered for precise, repeatable, and data-driven
protection tuning — essential for critical industrial machinery.
Key advantages of the HPL500:
- Peak Detector Memory: Captures and stores real-world min/max kW readings during operation.
Engineers can then define exact underload (e.g., dry pump) and overload (e.g., jam) trip thresholds based on
data, not estimation.
- Configurable Timers: Adjustable startup and reaction delays (0–999 s) allow accurate filtering
of inrush currents and transient load spikes.
- Flexible Relays: Two independent SPDT relays configurable as Min/Max, Min/Min, or Max/Max
for pre-alarm and trip logic.
- Dedicated Two-Speed Input: Digital input (S2) for switching between two active limit sets —
perfect for dual-speed motors.
4. Comparison Summary
| Feature |
Unipower HPL500 |
Emotron M20 (RS 6550141) |
| Voltage Range |
1×100–400 V & 3×100–575 V AC (universal) |
3×380–500 V AC (model specific) |
| Current Measurement |
Internal up to 40 A (no CT) |
External CT required |
| Setup Method |
Manual or data-driven with Peak Detector |
Auto-Set learns load profile |
| Outputs |
2×Relays (SPDT) + 0/4–20 mA output |
2×Relays + 0/4–20 mA output |
| Approx. RS Price (ex VAT) |
£653.53 |
£619.99 |
| Charter Controls List Price |
£526.66 |
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Conclusion: The Unipower HPL500 is the Clearer Choice for Engineers
The Emotron M20 is a capable monitor — but the Unipower HPL500 is the superior solution for UK
control panel builders and OEMs. It delivers:
- Lower total installed cost — no CT required up to 40 A.
- Unmatched flexibility — universal 100–575 V supply for any market.
- Advanced engineering control — peak memory, configurable timers, and two-speed input.
For applications where reliability, precision, and efficiency matter, the Unipower HPL500 stands as
the definitive load monitor.
Explore the full Unipower range at
Charter Controls.