Electronic Protection Relays

Q: Why does voltage asymmetry cause electric motors to overheat?

Even a small 3% voltage unbalance causes a disproportionately high 18% to 25% current unbalance in motor windings, creating reverse torque, excessive heating, and premature motor burnout. Lovato PMV relays detect asymmetry and trip before winding insulation is damaged.

Q: Can Earth leakage relays be coordinated with upstream breakers?

Yes. By adjusting the trip current threshold (IΔn) and time delay (Δt) on our Lovato R2D/R4D relays, we achieve full selectivity between sub-feeders and the main switchboard incomer.

Microprocessor relays for voltage monitoring, phase loss, Earth leakage, and motor thermal protection

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Electronic Protection Relays

Electrical equipment is highly vulnerable to power quality anomalies including phase failure, voltage asymmetry, over/under-voltage, and Earth leakage faults. Nairobi Power Engineers supplies and integrates Lovato Electric microprocessor-based protection relays designed to trip switchgear before expensive damage occurs.

Our range includes Lovato PMV/PMA voltage and phase monitoring relays, TM series motor thermal and thermistor relays, and R2D/R4D Earth leakage relays with external core balance toroid sensors for complete switchboard and machinery safety.

Equipment & Range Highlights

Lovato PMV / PMA • Voltage Monitoring

Conceptual monitoring relays scene; exact specifications vary.

3-Phase Voltage & Phase Failure Relays

DIN-rail electronic relays monitoring phase loss, neutral loss, incorrect phase sequence, overvoltage, undervoltage, and phase asymmetry.

FunctionsPhase Loss • Sequence • Asymmetry

Voltage Range208 V – 480 V AC

Output1 / 2 SPDT 8A Contacts

Lovato R2D / R4D • Earth Leakage

Conceptual electronic protection relays scene; exact specifications vary.

Adjustable Earth Leakage Relays with Toroids

Core-balance Earth leakage relays with adjustable current sensitivity (30mA to 30A) and selectable time delay (instantaneous to 5s).

Sensitivity0.03 A to 30 A Adjustable

Delay0.05 s to 5.0 s

Toroids35 mm to 210 mm Diameter

Protection Relay Technical Reference

Relay Model	Monitored Parameter	Trip Thresholds	Output Configuration
Lovato PMV10 / PMV20	Phase Loss, Phase Sequence, Neutral Loss	Fixed thresholds (< 70% Un)	1 SPDT 8A 250V AC relay
Lovato PMV50 / PMV70	Overvoltage, Undervoltage, Asymmetry	Over: 105–115%, Under: 80–95%, Asym: 5–15%	2 SPDT 8A with adjustable delay 0.1–20s
Lovato R2D / R4D	Type A / AC Earth Residual Current	IΔn: 0.03 A – 30 A (9 steps)	1 Pre-alarm + 1 Main Trip Contact
Lovato TM P	PTC Motor Temperature Sensor Input	Trip at PTC R > 3.1 kΩ, Reset < 1.6 kΩ	1 SPDT 8A contact with manual/auto reset

Engineering & Build Highlights

True RMS voltage sensing guarantees accurate protection even on distorted harmonic generator supplies
Adjustable tripping delay timers prevent nuisance tripping during motor starting and temporary line dips
Compact 1-module (17.5mm) and 2-module (35mm) DIN-rail mounting formats save critical panel space
Fail-safe operating principle: output relay de-energizes upon fault detection or auxiliary power loss
Clear LED diagnostic indicators for Power On, Relay State, and specific fault type identification
NFC smartphone programming available on advanced models for rapid setting verification

Target Applications & Sectors

Motor control centres & borehole pump starter panelsStandby generator & automatic transfer switch (ATS) panelsMain LV distribution switchboard Earth leakage protectionRefrigeration chiller & cold room compressor protectionAir conditioning air handling units & cooling towersIndustrial automation machinery & conveyor lines

Even a small 3% voltage unbalance causes a disproportionately high 18% to 25% current unbalance in motor windings, creating reverse torque, excessive heating, and premature motor burnout. Lovato PMV relays detect asymmetry and trip before winding insulation is damaged.

Yes. By adjusting the trip current threshold (IΔn) and time delay (Δt) on our Lovato R2D/R4D relays, we achieve full selectivity between sub-feeders and the main switchboard incomer.

Protect Your Motors & Switchgear

Contact our protection engineers for technical advice on voltage and Earth leakage relay selection.

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