Overload Relay Rating Chart: Quick Reference by Motor Size
The overload relay rating chart below gives a quick reference for selecting overload protection based on common motor sizes. Use it as a starting point before checking the motor nameplate current.
Table of Contents
Table of Contents
| Motor Rating (kW) | Motor Rating (HP) | Full Load Current (FLA) @ 415V | Recommended Overload Relay Rating | Setting Range |
|---|---|---|---|---|
| 0.37 | 0.5 | 1.1A | 1–1.6A | 1.1A–1.2A |
| 0.75 | 1 | 1.8A | 1.6–2.5A | 1.8A–2.0A |
| 1.5 | 2 | 3.2A | 2.5–4A | 3.2A–3.5A |
| 2.2 | 3 | 4.8A | 4–6A | 4.8A–5.2A |
| 3.7 | 5 | 7.5A | 6–10A | 7.5A–8A |
| 5.5 | 7.5 | 11A | 9–14A | 11A–12A |
| 7.5 | 10 | 14.5A | 13–18A | 14.5A–15A |
| 11 | 15 | 21A | 18–25A | 21A–22A |
| 15 | 20 | 28A | 24–32A | 28A–30A |
| 18.5 | 25 | 34A | 30–40A | 34A–36A |
| 22 | 30 | 42A | 37–50A | 42A–44A |
| 30 | 40 | 56A | 48–65A | 56A–60A |
| 37 | 50 | 68A | 63–80A | 68A–72A |
| 45 | 60 | 82A | 80–100A | 82A–86A |
| 55 | 75 | 100A | 95–120A | 100A–105A |
This overload relay rating chart helps electricians, panel builders, and maintenance engineers choose a suitable thermal overload relay for motor protection.
For non-standard motor sizes not in the chart, you can use our Motor Overload Setting Calculator
How to Use This Chart
Using an overload relay rating chart is simple if you follow the right process.
Step 1: Identify the Motor Power
Check the motor power in kW or HP from the nameplate.
Step 2: Find the Matching Row
Locate the same motor rating in the overload relay rating chart.
Step 3: Confirm Full Load Current
Compare the listed FLA with the actual motor nameplate current. Real motors can vary due to efficiency, power factor, and manufacturer design. Use our Motor Current Calculator
Step 4: Set the Relay
Adjust the overload relay close to 100% to 115% of the motor full load current depending on application.
Important note:
- For standard squirrel cage motors, set near 100% FLA
- For high starting torque motors, allow 110% to 115%
- For service factor motors, check manufacturer recommendations
Example:
A 7.5kW motor with a nameplate current of 15A should use an overload relay range of 13–18A and set around 15A.
Find all about How to Size Motor Overload Protection Step-by-Step Guide
Overload Relay Rating Chart by Voltage
Voltage affects motor current directly. Lower voltage means higher current for the same output power. This overload relay rating chart by voltage shows how relay selection changes.
230V Motor Overload Chart
| Motor kW | FLA | Relay Range |
|---|---|---|
| 1.5 | 5.8A | 4–6A |
| 3.7 | 13A | 9–14A |
| 7.5 | 24A | 18–25A |
| 15 | 46A | 37–50A |
400V Motor Overload Chart
| Motor kW | FLA | Relay Range |
|---|---|---|
| 1.5 | 3.3A | 2.5–4A |
| 3.7 | 7.8A | 6–10A |
| 7.5 | 15A | 13–18A |
| 15 | 29A | 24–32A |
Use our online tool Motor Overload Setting Calculator
415V Motor Overload Chart
| Motor kW | FLA | Relay Range |
|---|---|---|
| 1.5 | 3.2A | 2.5–4A |
| 3.7 | 7.5A | 6–10A |
| 7.5 | 14.5A | 13–18A |
| 15 | 28A | 24–32A |
690V Motor Overload Chart
| Motor kW | FLA | Relay Range |
|---|---|---|
| 1.5 | 1.9A | 1.6–2.5A |
| 3.7 | 4.4A | 4–6A |
| 7.5 | 8.6A | 6–10A |
| 15 | 16.7A | 13–18A |
This overload relay rating chart by voltage is useful for industrial control panels and MCC applications where system voltage varies.
Know more about how to calculate overload relay for motor
Overload Relay Rating Chart for 3-Phase Motors
For three-phase motors, relay selection is usually based on current ranges. This format helps when you already have the motor current but need a relay.
| Relay Rating Range | Suitable Motor Current | Typical Motor Size |
|---|---|---|
| 1–1.6A | 1.1A–1.5A | 0.37–0.55kW |
| 1.6–2.5A | 1.6A–2.4A | 0.75–1.1kW |
| 2.5–4A | 2.5A–3.9A | 1.5–2.2kW |
| 4–6A | 4A–5.9A | 2.2–3kW |
| 6–10A | 6A–9.9A | 3.7–5.5kW |
| 9–14A | 9A–13.9A | 5.5–7.5kW |
| 13–18A | 13A–17.9A | 7.5–11kW |
| 18–25A | 18A–24.9A | 11–15kW |
| 24–32A | 24A–31.9A | 15–18.5kW |
| 30–40A | 30A–39.9A | 18.5–22kW |
| 37–50A | 37A–49.9A | 22–30kW |
This overload relay rating chart is practical for motor starters, DOL starters, and star-delta starter circuits.
Know more about sizing motor overload protection
Motor Overload Sizing Chart (Special Duty Motors)
Not all motors run under normal conditions. Some applications need extra attention.
Special duty examples include:
- Crushers
- Conveyors
- Compressors
- Centrifuges
- Hoists
- Mixers
Find the exact setting using our Motor Overload Setting Table which includes 3 Phase Chart & Complete Guide
These motors often have:
- High starting current
- Long acceleration time
- Frequent starts and stops
- Heavy mechanical load
| Motor Type | Recommended Setting |
|---|---|
| Standard duty | 100% FLA |
| High inertia load | 110% FLA |
| Frequent starts | 110%–115% FLA |
| Heavy shock load | 115% FLA |
In these cases, the overload relay rating chart should only be used as a guide. Always review duty cycle and service factor.
Find all about overload relay working principle
Motor Overload Protection Chart vs. Setting Table — What’s the Difference?
Many people confuse these two.
Here is the difference.
| Type | Purpose | Based On |
|---|---|---|
| Overload Protection Chart | Helps choose relay range | Motor size and FLA |
| Overload Setting Table | Helps set the selected relay | Actual nameplate current |
The overload relay rating chart is used first during selection.
The setting table comes after when adjusting the dial.
For example:
If your motor current is 28A:
- Use the overload relay rating chart to choose 24–32A relay
- Use the setting table to adjust the dial exactly to 28A
This method improves motor protection and reduces nuisance tripping.
Find all about How to Set Thermal Overload Relay Setting
Frequently Asked Questions
What is the standard overload relay rating chart?
A standard overload relay rating chart lists motor size, full load current, relay range, and setting values. It acts as a quick guide for selecting thermal overload protection.
How do you match overload relay rating to motor size?
Find the motor kW or HP, check its FLA, and select a relay range that covers the motor current. Always confirm with the nameplate.
Does overload relay rating change with voltage?
Yes. Lower voltage increases current, so the overload relay range can change even for the same motor size.
What’s the difference between an overload chart and a setting table?
An overload chart helps select the relay. A setting table helps adjust the relay after installation. Both are important for proper motor protection.
Using an overload relay rating chart correctly improves motor safety, extends equipment life, and prevents overload damage. Whether you are designing a control panel or maintaining an industrial motor, this quick reference makes relay selection faster and more accurate.
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