Motor Fuse Size Calculator

To determine the appropriate fuse size for a motor, you should first identify the motor’s full load current (FLA) from its nameplate or specifications. Then, select a fuse with a current rating slightly higher than the FLA to provide proper protection while accommodating inrush current during startup. Always follow electrical code requirements and consult a qualified electrician if needed.

Creating a table to help you determine motor fuse sizes based on motor power ratings and voltage. Please note that these values are approximate and should be confirmed with applicable electrical codes and standards.

Motor Power (kW)	Motor Voltage (V)	Full Load Current (FLA) Estimate (Amps)	Recommended Fuse Size (Amps)
1 kW	230 V	4.3 - 4.7	5 A
3 kW	230 V	13 - 15	20 A
5 kW	230 V	21 - 23	25 A
7.5 kW	230 V	32 - 35	40 A
10 kW	230 V	43 - 47	50 A
15 kW	230 V	65 - 70	80 A
22 kW	400 V	31 - 35	40 A (3-phase)
30 kW	400 V	42 - 47	50 A (3-phase)
45 kW	400 V	64 - 70	80 A (3-phase)
55 kW	400 V	78 - 85	100 A (3-phase)

These values serve as estimations. Always consult with a qualified electrician and refer to applicable electrical codes and standards for precise sizing and safety considerations.

FAQs

How do you size fuses for a motor?

Sizing fuses for a motor involves calculating the motor's full load current (FLA) and selecting a fuse with a current rating slightly higher than the FLA. The specific steps depend on factors like the motor type (single-phase or three-phase), voltage, and starting characteristics.

How do I calculate what size fuse I need?

To calculate the fuse size for a motor, follow these steps:

1. Determine the motor's full load current (FLA) from its nameplate or motor data sheet.
2. Choose a fuse with a current rating greater than the FLA but not too high to prevent overload protection.

What size fuse for a 15kW motor?

For an estimation, a 15kW motor at 230V typically has an FLA of around 65-70 amps, so you might use a 75-80 amp fuse.

What fuse should I use calculator?

There are online fuse calculators available, but it's essential to understand the principles behind fuse sizing to use them effectively.

What is the best fuse for a motor?

The best fuse for a motor depends on factors like motor type, FLA, and starting characteristics. A time-delay (slow-blow) fuse is often suitable for motors to accommodate inrush current during startup.

What is the fuse rating for a 10 hp motor?

For an estimation, a 10hp motor at 230V typically has an FLA of around 30-35 amps, so you might use a 40-45 amp fuse.

What is the rule of thumb for fuse sizing?

A common rule of thumb is to select a fuse with a rating 150% to 175% of the motor's FLA to allow for inrush current.

How do you size a fuse for a 3-phase motor?

For a 3-phase motor, calculate the FLA using the formula: FLA = (kW * 1000) / (1.732 * Voltage). Then select a fuse with a rating greater than the calculated FLA.

What happens if the fuse rating is too high?

If the fuse rating is too high, it may not provide adequate protection for the motor. In case of a fault or overload, the motor might sustain damage before the fuse blows.

What is the current of a 22kW motor?

Assuming a 400V 3-phase motor, a 22kW motor typically has an FLA of around 40-45 amps.

How many amps is a 20 hp motor?

For an estimation, a 20hp motor at 230V typically has an FLA of around 60-70 amps.

What MCB is required for a 5 hp motor?

For an estimation, a 5hp motor at 230V typically has an FLA of around 15-20 amps, so you might use a 25-30 amp Miniature Circuit Breaker (MCB).

What is a motor-rated fuse?

A motor-rated fuse is a fuse specifically designed for motor protection. It can handle the inrush current that occurs during motor startup without blowing prematurely.

Can I use a 13A fuse instead of 5A?

Using a 13A fuse instead of a 5A fuse may lead to inadequate protection and potentially damage the circuit or equipment. It's not recommended unless it's determined to be safe and appropriate by a qualified electrician.

Do the numbers on fuses matter?

Yes, the numbers on fuses indicate their current rating. It's crucial to use a fuse with the correct current rating for the circuit or equipment.

Should I use a 3A or 13A fuse?

Use the fuse rating specified by the equipment manufacturer or a qualified electrician. Using the wrong fuse rating can be dangerous.

How do I choose a fuse for my DC motor?

Select a fuse for a DC motor by determining the motor's full load current (FLA) and choosing a DC-rated fuse with a rating slightly higher than the FLA.

How many amps should my fuse be?

The fuse rating depends on the motor's FLA. Choose a fuse rating higher than the FLA, typically by 150% to 175%.

Can I use a 10A fuse instead of 12A?

Using a 10A fuse instead of a 12A fuse may be acceptable if it's within the tolerance range of the equipment and circuit. However, it's best to follow the manufacturer's recommendations.

What size breaker do I need for a 10 hp motor?

For an estimation, a 10hp motor at 230V typically requires a circuit breaker with a rating of around 40-50 amps.

Can I use a 13A fuse instead of 10A?

Using a 13A fuse instead of a 10A fuse may lead to overcurrent protection issues. It's essential to use the correct fuse rating for safety.

Can you use too big of a fuse?

Using a fuse that is significantly larger than required can result in inadequate protection, potentially damaging equipment or causing safety hazards.

Does the 80% rule apply to fuses?

The 80% rule, which suggests derating conductors to 80% of their ampacity, may apply to fuses in certain situations to account for inrush current during motor startup.

How many amps is a 7.5 hp motor?

For an estimation, a 7.5hp motor at 230V typically has an FLA of around 30-35 amps.

What size breaker do I need for a 2hp motor?

For an estimation, a 2hp motor at 230V typically requires a circuit breaker with a rating of around 10-15 amps.

What size breaker do I need for a 3-phase motor?

For a 3-phase motor, the breaker size depends on the motor's FLA and voltage. It's typically calculated using the FLA and specific code requirements.

What does F mean on a fuse?

The "F" on a fuse may indicate that it's a fast-acting fuse, designed to blow quickly when an overcurrent condition occurs.

How do you tell if a fuse is overloaded?

An overloaded fuse may show signs of melting, discoloration, or a broken filament inside. It's crucial to replace a fuse that has experienced overload.

Is it better to have a higher or lower fuse?

It's better to have a fuse with a rating slightly higher than the required current to prevent nuisance trips, but it should not be significantly higher to maintain safety.

What is the difference between 7kW and 22kW?

The difference between 7kW and 22kW is the power output. 22kW is a higher power rating than 7kW, indicating that a device or motor with 22kW can produce more work or output.

How many amps is a 5hp motor 3 phase 415V?

For an estimation, a 5hp 3-phase motor at 415V typically has an FLA of around 8-10 amps.

Can you get 22kW from single phase?

No, 22kW typically exceeds the power capacity of a single-phase system. It's more commonly associated with three-phase power.

How many amps does a 30 hp motor draw at 480 volts?

For an estimation, a 30hp motor at 480V typically has an FLA of around 40-45 amps.

How many kW can 20 amps take?

The power (kW) that 20 amps can handle depends on the voltage. For example, at 230V, 20 amps can handle up to approximately 4.6 kW.

How many amps is a 25 hp motor?

For an estimation, a 25hp motor at 230V typically has an FLA of around 80-90 amps.

Can I use MCB for a motor?

Yes, you can use a Miniature Circuit Breaker (MCB) to protect a motor, but it should be appropriately sized for the motor's current requirements.

How do you size an MCB for a motor?

Size an MCB for a motor by determining the motor's FLA and selecting an MCB with a rating equal to or slightly higher than the FLA.

What size MCB for a 2.2 kW motor?

For a 2.2 kW motor, you might use an MCB with a rating of around 10-15 amps, depending on the voltage and motor characteristics.

What rating is a 2 kW fuse?

For a 2 kW motor, you might use a fuse with a rating of around 10-15 amps, depending on the voltage and motor characteristics.

How do you size a motor overload?

Motor overload protection is typically sized based on the motor's FLA and the desired level of protection. It involves selecting an overload relay or thermal protection device that matches the motor's requirements.

What is a 13A fuse rating?

A 13A fuse rating means the fuse can handle a maximum current of 13 amperes before blowing.

Why do we need a 5A fuse?

A 5A fuse is used to protect electrical circuits and devices that require a current rating of up to 5 amperes. It prevents excessive current from damaging the circuit or equipment.

What are 5A fuses used for?

5A fuses are used for various low-power electrical applications, such as lighting circuits, small appliances, and electronics.

What does a 5A fuse do?

A 5A fuse acts as a safety device in an electrical circuit. It will blow (open) if the current exceeds 5 amperes, thereby protecting the circuit from overcurrent and potential damage.

What happens if you use the wrong size fuse?

Using the wrong size fuse can lead to inadequate protection or nuisance trips. It can also pose a safety hazard by allowing excessive current to flow through the circuit.

What happens if you put a fuse in backward?

Fuses are designed to work in one direction, and inserting them backward may result in improper protection or no protection at all. Always install fuses correctly.

What does the letter E mean on a fuse?

The letter "E" on a fuse may indicate that it's a European-style fuse, which follows specific international standards for fuse design.

What happens if you put a 13 amp fuse instead of a 3 amp?

Using a 13 amp fuse instead of a 3 amp fuse in a circuit with a 3 amp requirement can overload the circuit and potentially cause damage or overheating.

What happens if you use a 13 amp fuse instead of a 5 amp?

Using a 13 amp fuse instead of a 5 amp fuse can overload the circuit, potentially damaging equipment or causing a fire hazard.

What happens if you use a 13 amp fuse instead of a 3 amp?

Using a 13 amp fuse instead of a 3 amp fuse can overload the circuit and lead to overheating or damage to the circuit and connected devices.

How do I choose a fuse for my motor?

Choose a fuse for your motor by calculating the motor's FLA and selecting a fuse with a rating slightly higher than the FLA to account for inrush current during startup.

What size fuse for a 15 kW motor?

For a rough estimation, a 15 kW motor at 230V may have an FLA of around 65-70 amps, so you might use a 75-80 amp fuse.

How do I calculate which fuse to use?

Calculate the fuse size by determining the motor's FLA and choosing a fuse with a rating greater than the FLA but not excessively high.

How do I know what size fuse I need?

You know the fuse size you need by calculating the motor's FLA and selecting a fuse with a rating slightly higher than the FLA to provide adequate protection.