Motor Protection Selector + Motor Run Cost Calculator + VFD Calculator

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CircuitSecrets Motor Suite

Professional Web Tools for Electrical Engineers

IEC 60947 · IEC 60034 Compliant

⚡ Enter motor nameplate data to get fully calculated IEC-compliant protection recommendations — MCCB/MPCB, contactors, overload relay, cable size, and fuse rating.

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Motor Parameters

Motor Power (kW)

Supply Voltage 220 V — 1-Phase 380 V — 3-Phase 400 V — 3-Phase 415 V — 3-Phase 440 V — 3-Phase 660 V — 3-Phase

Power Factor (cos φ)

Typical: 0.80 – 0.92

Motor Efficiency (%)

IE2: 88–93%, IE3: 91–95%

Starting Method DOL — Direct On-Line Star-Delta (Y-Δ) Soft Starter VFD / Inverter Drive

Service Factor 1.0 — Standard 1.15 — Heavy Duty 1.25 — Very Heavy Duty

Duty Cycle S1 — Continuous S2 — Short Time S3 — Intermittent

Motor Poles 2P — 3000 rpm (50Hz) 4P — 1500 rpm (50Hz) 6P — 1000 rpm (50Hz) 8P — 750 rpm (50Hz)

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Protection Recommendations

Enter motor parameters and click Calculate

💡 Calculate motor electricity consumption and running cost. Includes BDT pricing presets from BPDB tariff schedule, CO₂ emission, and efficiency improvement savings.

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Operating Parameters

Motor Power (kW)

Motor Efficiency (%)

Power Factor

Load Factor (%)

% of full load running

Hours per Day

Working Days / Month

BPDB Tariff Preset — Select Category — Residential (LT) — ৳7.43/kWh Small Industry (LT) — ৳8.20/kWh General Purpose (LT) — ৳9.10/kWh Medium Voltage Industry — ৳10.40/kWh High Voltage Industry — ৳11.87/kWh

Electricity Tariff (BDT / kWh)

Number of Motors (same rating)

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Cost Analysis

Enter parameters to see cost breakdown

🔄 Calculate VFD energy savings using the Affinity Law (cube law for centrifugal loads). Get VFD sizing recommendation, annual BDT savings, and investment payback period.

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VFD Parameters

Motor Power (kW)

Supply Voltage 220 V — 1-Phase 380 V — 3-Phase 400 V — 3-Phase 415 V — 3-Phase

Base Speed (%)

Current / maximum speed

Reduced Speed (%)

Target VFD running speed

Load Type Centrifugal — Fan / Pump (Cube Law P ∝ N³) Constant Torque — Conveyor / Compressor (P ∝ N) Quadratic — Mixed Centrifugal (P ∝ N²)

Centrifugal loads give maximum energy savings with VFD

Hours per Day

Operating Days / Year

Energy Tariff (BDT / kWh)

VFD Purchase Cost (BDT)

For payback period calculation

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VFD Savings Analysis

Enter parameters to calculate energy savings

CircuitSecrets Motor Engineering Suite · Built for Professional Electrical Engineers · IEC 60947 / IEC 60034 / IEC 60364

Results are engineering recommendations based on standard calculations. Always verify with manufacturer datasheets and local wiring regulations (BNBC / BREB).