Motor Overload Setting Table: 3 Phase Chart & Complete Guide

Electric motors are the backbone of industrial systems, from pumps and conveyors to compressors and HVAC equipment. But every motor needs proper protection against overcurrent and overheating. This is where a Motor Overload Setting Table becomes essential.

A correctly adjusted overload relay protects the motor from excessive current while allowing normal startup conditions. If the setting is too low, the motor trips unnecessarily. If it is too high, the motor winding can overheat and fail.

This guide explains everything about overload settings, how to read a motor overload setting table, how to size overload protection, and how to calculate the right overload value for 3-phase motors.

The purpose of the motor overload setting table is to match the protection device with the motor’s full-load current (FLC). This ensures that the motor operates within its thermal limit. Let’s explore how this table works and why it matters.

What is a Motor Overload Setting Table?

A Motor Overload Setting Table is a reference chart used to set thermal overload relays based on motor full load current (FLA). It helps electricians, technicians, and engineers quickly select the correct overload range without performing complex calculations every time.

The overload relay monitors the motor current. If the motor draws more than its rated current for a long period, the relay trips and disconnects power.

The main purpose of the table is to:

• Protect motor windings from overheating
• Prevent insulation damage
• Reduce downtime
• Increase motor life
• Improve system reliability

A standard motor overload setting table usually includes:

This table is widely used in motor control panels, MCCs, and industrial distribution systems.

3 Phase Motor Overload Setting Table (Quick Reference)

Below is a quick reference Motor Overload Setting Table for common 3-phase motors at 415V.

This 3 phase motor overload setting table is based on standard induction motors with normal service factors.

Actual values may vary depending on motor efficiency, power factor, and manufacturer data.

How to Read and Apply the Overload Setting Table

Using the Motor Overload Setting Table is simple if you follow the right steps.

Step 1: Find the Motor Nameplate Current

Every motor has a nameplate showing:

• Rated voltage
• Full load current
• Frequency
• RPM
• Power factor

Always use the nameplate FLA if available.

Example:

If a 15kW motor shows 28A FLA, use that value.

Step 2: Match with the Overload Range

Look for the overload relay range covering 28A.

Example:

24–32A relay.

Step 3: Adjust the Relay

Set the overload dial close to 28A.

This ensures proper motor thermal protection.

Step 4: Consider Service Factor

Some motors have service factor above 1.15. In such cases, settings may be increased slightly.

Quick application table:

Proper application improves trip accuracy and motor safety.

Motor Overload Setting Table Download PDF

Many engineers prefer a downloadable Motor Overload Setting Table for field work, panel building, and maintenance.

PDF and XLS versions are useful because they allow:

• Quick offline access
• Fast motor lookup
• Easy overload sizing
• Site troubleshooting
• Panel design reference

Recommended file formats:

A downloadable table should include:

Download the Motor overload setting Table in PDF format right here.

• kW to current chart
• HP to current chart
• Relay ranges
• Trip class
• Protection notes

How to Size Motor Overload Protection

Correct sizing is critical. Oversized overloads fail to protect. Undersized overloads cause nuisance trips.

Follow this process.

1. Identify Full Load Current

Use the motor nameplate.

2. Select Relay Range

The overload relay range must include the motor FLA.

Example:

Motor FLA = 41A

Choose 37–50A relay.

3. Apply Standard Percentage

Most standards use:

• 100% for standard motors
• 115% for motors with service factor

Sizing example:

4. Check Start Current

Motors may draw 5 to 7 times FLA during startup.

The overload should allow this temporary current.

5. Match Trip Class

Trip classes affect protection speed.

This method ensures proper overload protection sizing. Follow the complete guide here.

Thermal Overload Relay Setting

A thermal overload relay works by sensing heat generated by motor current. It protects against prolonged overload conditions.

Thermal overload relay setting depends on:

• Full load current
• Ambient temperature
• Duty cycle
• Starting frequency

Common relay types:

Best practices for thermal overload setting:

• Use motor nameplate current
• Avoid guessing current values
• Verify with clamp meter
• Check phase balance
• Test trip operation

Improper thermal overload relay setting can shorten motor life significantly.

Overload Relay Rating Chart

An overload relay rating chart helps in selecting relay sizes quickly.

Below is a practical chart.

This overload relay rating chart simplifies selection for motor control applications.

It also helps in MCC panel design and maintenance planning.

How to Calculate Motor Overload Setting

Sometimes you may need to calculate overload settings manually.

The basic formula is:

Overload Setting = Motor Full Load Current × Adjustment Factor

For standard motors:

Overload Setting = FLA × 1.0

For service factor motors:

Overload Setting = FLA × 1.15

Example 1:

Motor FLA = 20A

Standard setting:

20 × 1.0 = 20A

Example 2:

Motor FLA = 20A

Service factor setting:

20 × 1.15 = 23A

For three-phase motors, FLA can be calculated as:

FLA = P ÷ (√3 × V × PF × Efficiency)

Where:

• P = Power in watts
• V = Voltage
• PF = Power factor

Calculation table:

This method supports overload setting calculation when nameplate data is missing.

Motor Overload Setting Calculator

A Motor Overload Setting Calculator makes the process faster and more accurate.

Instead of manual calculations, the tool can instantly calculate:

• Full load current
• Recommended overload setting
• Relay size
• Trip class suggestion

Inputs required:

• Motor power
• Voltage
• Power factor
• Efficiency
• Service factor

Output example:

A calculator is useful for:

• Electricians
• Panel builders
• Maintenance engineers
• Motor installers

It reduces human error and improves setup speed.

Motor Overload Setting Table (Three-Phase Motors)

Here’s a sample table for standard 3-phase induction motors running at 400V, 50 Hz.

These values may slightly vary depending on the manufacturer and efficiency class of the motor.

3 Phase Motor Overload Setting Table

A 3 phase motor overload setting table helps electricians and technicians set the correct overload relay based on motor full load current (FLC). In any motor overload setting table, the overload relay is usually adjusted at 115% to 125% of the motor rated current, depending on service factor and application. Correct settings protect the motor from overheating, phase loss, and excessive current draw.

Know more about How to Check 3 Phase Motor Winding with Multimeter

Standard 3 Phase Motor Overload Setting Table

Overload Relay Cost for 3 Phase Motors

The cost of overload relays depends on current range, brand, and trip class. Small relays (1–10A) usually cost around $15–$40, while medium-size relays (10–40A) range between $40–$120. Heavy-duty industrial overloads can exceed $200. Using a proper motor overload setting table before purchasing ensures accurate relay selection and avoids unnecessary replacement costs.

Know more about How to Check 3 Phase Motor Winding with Multimeter

Tips for Accurate Overload Settings

• Always match the relay setting to the actual current, not just the nameplate.
• Use Motor Circuit Protection Tables to verify compatibility between cable size, breaker size, and relay setting.
• If your motor is running in a high-temperature environment, derate the overload relay setting.
• Motors operating with frequent starts may need a lower setting.

Thermal vs Electronic Overload Relays

Thermal overload relays use bimetallic strips that bend when heated. They are simple, low-cost, and suitable for most motors. But they react slower and less accurately.

Electronic overload relays are more accurate. They can detect phase imbalance, ground faults, and have adjustable trip classes. These are ideal for precision control applications and large motors.

In either case, the motor overload setting table helps to ensure you’re applying the right settings.

Know more about Motor Starter Size Chart

Common Motor Overload Mistakes to Avoid

1. Ignoring Full Load Current (FLC)
   Always refer to FLC, not just HP or kW.
2. Setting Too Low
   This causes nuisance trips.
3. Setting Too High
   This exposes the motor to overheating.
4. Using the Wrong Relay Type
   Some relays are not meant for heavy-duty motors or variable frequency drives.
5. Not Considering Ambient Temperature
   Temperature derating is often ignored but is critical for accuracy.

Know more about Motor Overload Protection Chart

Special Considerations for Overload Settings

• Star-Delta Starters: The relay should be placed in the line side, not delta side.
• Soft Starters: Allow for extended acceleration time. Set the relay at the higher end of the range.
• Variable Frequency Drives (VFDs): Use the VFD’s built-in protection settings, not external relays.

In each case, reference the motor overload setting table to determine the most suitable base values.

Summary and Best Practices

Understanding and using the motor overload setting table properly is essential for efficient motor protection. These settings protect your investment, reduce downtime, and prevent hazards.

Always:

• Start with the motor’s full-load current.
• Use the manufacturer’s recommendations.
• Factor in environment and duty cycle.
• Match the relay or MPCB setting accordingly.
• Double-check with Overload Setting for Motor guides or Motor Circuit Protection Tables.

Proper overload setting is a small step, but one with major consequences. An accurately set relay is the difference between years of motor operation and premature failure.

Use our online tool for free Wire Size Calculator for Motors – Accurate Motor Cable Sizing Tool for Electric Loads

Frequently Asked Questions

A Motor Overload Setting Table is one of the most practical tools for safe motor operation. Whether you are installing a new motor, troubleshooting overload trips, or designing a control panel, using the right overload settings can prevent costly failures and improve equipment life.

Use our online tool motor cable size calculator

Follow Us on Social:

• LinkedIn
• Facebook
• Pinterest
• Threads
• X

Subscribe our Newsletter on Electrical Insights for latest updates from Electrical Engineering Hub

#MotorProtection, #OverloadRelay, #MotorOverloadSetting, #ElectricalEngineering, #MotorStarter, #OverloadProtection, #ElectricalSafety, #IndustrialAutomation, #ControlPanelDesign, #MotorCurrent, #OverloadRelaySettings, #MotorControl, #ElectricalMaintenance, #IECStandards, #ThermalOverloadRelay