WAZIPOINT · Engineering Tools

⏚ Electric Fuse Rate Calculator

Determine the correct fuse rating per IEC 60269 / IS 13703 practice

1 · Supply & Load Type

Supply System Single Phase (230V) Three Phase (400V)

Load Type General / Lighting Load Motor Load Transformer Load

Fuse Type HRC Cartridge Fuse Rewireable (Semi-enclosed)

Input Mode

2 · Load Data

Full Load Current, FLC (A)

Load Power (kW)

Power Factor

Voltage is taken from the supply system selected above (editable field below).

Voltage (V)

Result

Recommended Fuse Rating

— A

Standard Multiplying Factors (Reference)

General / Lighting Load — HRC	1.25 × FLC
General / Lighting Load — Rewireable	1.5 × FLC
Motor Load — HRC (allows starting surge)	1.75–2.0 × FLC
Motor Load — Rewireable	2.0–2.5 × FLC
Transformer Load (inrush allowance)	1.5–2.0 × FLC

Factors follow common IEC 60269 / IS 13703 / BS 88 engineering practice. Always cross-check against the manufacturer's fuse curve and the upstream cable's current-carrying capacity (IEC 60364-5-52 / IS 732), so the fuse protects the conductor, not just the load.

WAZIPOINT Engineering Science & Technology  ·  wazipoint.com

An Electric Fuse Rate Calculator is essentially a tool used to determine the correct fuse rating for electrical circuits, ensuring protection against overcurrent while avoiding nuisance tripping. The fuse must be rated high enough to handle normal operating current but low enough to blow during fault conditions.

Fuse Rating Formula

The general formula used is:

$$$$Fuse Rating=Current Load×Safety Factor

• Current Load (I): The actual current drawn by the device or circuit.

• Safety Factor: Typically between 1.25 and 1.5 (to account for inrush currents and minor fluctuations).

Step-by-Step Calculation

1. Determine load current. Example: A motor rated at 2000 W operating at 230 V.

$$$$I=PV=2000230≈8.7 A

2. Apply safety factor

$$$$Fuse Rating=8.7×1.25≈10.9 A

3. Select the nearest standard fuse → Choose a 12 A fuse (since 10 A may blow during startup surge).

Typical Fuse Rating Guide

Appliance	Power (W)	Voltage (V)	Current (A)	Recommended Fuse
LED Bulb	15	230	0.065	0.5 A
Laptop	65	230	0.28	1 A
Microwave	1200	230	5.2	6.3 A
Air Conditioner	2000	230	8.7	12 A
Water Heater	3000	230	13	16 A

Key Considerations

• Fuse type: Fast-blow vs. slow-blow depending on load characteristics.

• Circuit voltage: Fuse must match or exceed system voltage.

• Environment: Temperature and installation conditions affect fuse performance.