What Is Temperature Rise in an Inductor and Why Does It Matter?

Temperature rise is an important parameter in power inductors and toroidal inductors.

It describes how much the temperature of the inductor increases after operating under a specified electrical load.

How Is Temperature Rise Calculated?

For example:

Ambient temperature: 25°C

Inductor operating temperature: 65°C

Temperature rise:

65°C - 25°C = 40°C

So the temperature rise is 40°C.

If a customer requires:

Temperature Rise ≤ 40°C

it generally means that under the specified test conditions, the inductor temperature should not increase by more than 40°C above ambient temperature.

Why Does an Inductor Heat Up?

One of the main sources of heat is copper loss in the winding.

The copper wire has electrical resistance, which is normally specified as DCR.

As current flows through the winding, heat is generated.

In general:

• Higher current tends to create more heat

• Higher DCR tends to create more heat

• Thicker wire tends to reduce DCR

• Better cooling helps reduce operating temperature

Core loss can also contribute to heating, especially in high-frequency applications.

Temperature Rise Is Not the Same as Operating Temperature

These two concepts are often confused.

For example:

Ambient temperature: 40°C

Inductor temperature: 75°C

The temperature rise is:

35°C

But the actual inductor operating temperature is:

75°C

Therefore, when reviewing an inductor specification, it is important to distinguish between:

• Operating temperature

• Temperature rise

Why Should Buyers Pay Attention to Temperature Rise?

Excessive temperature can affect:

• Product reliability

• Insulation life

• Copper winding performance

• Magnetic core performance

• Overall system efficiency

For this reason, customers should provide the expected operating current, ambient temperature and temperature rise requirement when requesting a custom inductor.

This information helps the manufacturer select a more suitable wire diameter, magnetic core and winding structure.