Imagine your newly launched electric vehicle catching fire on the road after running continuously for a few hours. People will lose trust in your brand and will prefer to stay away from your product lines considering their own safety.

One of the reasons for this mishap could be that the magnet wire for the EV motor had a suboptimal temperature rating.

What is Temperature Rating in copper winding wires?

Temperature Rating refers to the maximum temperature the enamelled copper wire can withstand without degrading. This is a specific temperature value in degree Celsius (°C) that the copper magnet wire’s insulation is guaranteed to withstand for a prolonged period.

For instance, an enamelled copper wire with a 180°C temperature rating means the insulation can safely operate at up to 180°C for extended periods.

Understanding the relationship between Temperature Rating and Thermal Class in Enamelled Copper Wires

Different insulation materials used on copper winding wires have different temperature ratings. To standardise this, the International Electrotechnical Commission (IEC) set a classification system called Thermal Class, through IEC 60085. 

Thermal class groups insulation materials based on their ability to handle continuous operating temperatures. Each class has a corresponding temperature range.

Class	A	E	B	F	H	K /N	R /M	C
Temperature °C	105	120	130	155	180	200	220	240+

 

These temperature classes can indicate which type of enamel best suits your application. When selecting a winding wire, it is crucial to consider both the temperature rating and the thermal class to ensure it meets the specific requirements of your application.

Thermal Class	105	120	130	155	180	200	220	240+
Insulation Material	Polyamide (Nylon) Polyvinyl Acetal, Formvar	Polyvinyl Acetal, Formvar	Polyurethane (solderable),  Polyester	Polyurethane (solderable), Polyester	Polyurethane (solderable), Polyester	Polyester (non-solderable)	Polyamide-imide	Polyimide

 

These enamels can be used as a single coat or as multiple coats (base coat, mid coat and top coats) to build a strong insulation system. Please note that in doing so, the thermal class of the final insulating system may be different than those of the individual materials.

Impact of temperature rating on enamelled copper wire performance

Apart from indicating safe operating temperatures, the temperature rating has a direct impact on enamelled copper wire features like:

Current Carrying Capacity:

A copper wire with a higher thermal rating can handle a larger current without overheating when compared to a wire with a lower rating. This is because the resistance of the enamelled copper wire increases with an increase in temperature. In wires with higher thermal classes, the insulation is designed to endure higher temperatures, which helps manage the increase in resistance and associated power losses effectively.

Lifespan of Insulation:

Exceeding this temperature rating accelerates the breakdown of the insulation, leading it to crack, become brittle, or even melt. This can cause electrical shorts, ground faults, and ultimately equipment failure.

Safety:

Overheating degrades insulation, increasing the risk of fire hazards. Selecting the correct temperature rating is essential to preserve insulation integrity and prevent electrical arcing and fires.

So, when choosing an insulation with a particular thermal class for copper winding wire consider these factors as well.

Tips to Choose Copper Winding Wires with the Right Temperature Rating

Copper winding wire is the hidden hero behind countless electrical devices, from the motors in your power tools to the transformers humming on the street. Follow these tips to select the right enamelled copper winding wire with the optimal temperature rating for your application:

Tip #1: Consider the operating Temperature:

When selecting a copper winding wire for your application, choose a wire with a temperature class exceeding the device’s operating temperature by a margin (e.g. 10-20 °C) to account for potential heat spikes and provide a safety buffer.

•   Example 1: A low-power transformer typically operates around 70°C. Select Class A (105°C) wire for a safety margin.
•   Example 2: A high-performance motor runs hot (around 120°C). Choose Class B (130°C) or higher rated wire for safe operation.

Tip #2: Consider Expected Thermal Life:

Enameled copper wires are typically rated for a minimum expected thermal life of 20,000 hours at their classified temperatures. However, if your application demands a longer lifespan, selecting a copper magnet wire with a higher temperature rating can be beneficial. Here’s why:

• Example 1: Industrial Fan Motor: Imagine an industrial fan motor designed to run continuously for 40,000 hours (over 4.5 years). While a Class F (155°C) wire might be sufficient for its typical operating temperature of 130°C, a Class H (180°C) wire could provide a longer lifespan due to the additional thermal headroom.
• Example 2: Oil Well Pump Motor: Downhole oil well pump motors operate in harsh environments with high ambient temperatures. Even if the motor itself runs at 150°C, a Class H (180°C) or even a higher-rated Class N (200°C) wire might be preferable for its improved heat tolerance over a longer period.

Tip #3: Consider other Thermal Properties required for your application:

While temperature rating is a crucial factor, other thermal properties of the copper magnet wire also influence performance. Here are two key properties to consider:

Heat Shock Resistance:

This refers to the wire’s ability to handle sudden temperature swings without the insulation cracking or delamination (peeling off). This is important in applications prone to rapid temperature changes during operation or startup.

• Example 1: Compressor Startup: A compressor motor experiences a significant temperature rise during startup. A wire with good heat shock resistance, like one with PEI+PAI insulation having a thermal class 200, can better withstand this rapid change.
• Example 2: Automotive Applications: Electric Vehicle traction motors experience fluctuating temperatures. Selecting magnet wire with high heat shock resistance, like polyimide insulation, can ensure reliable operation under these varying conditions.

Thermal Conductivity:

This refers to the insulation’s ability to transfer heat generated by the copper conductor outwards. Efficient heat dissipation is essential for preventing overheating and maintaining the desired operating temperature within the motor.

• Example 1: High-Efficiency Motors: Modern motors strive for high efficiency, minimising wasted energy as heat. Here, choosing a wire with good thermal conductivity, like copper magnet wire with polyimide film insulation, can help transfer heat away from the conductor and maintain optimal motor performance.
• Example 2: Transformers in Tight Spaces: Transformers placed in confined spaces with limited airflow require efficient heat dissipation. Selecting copper winding wire with high thermal conductivity can help prevent overheating and potential transformer failure.

 

As you can see from this, choosing the right temperature rating optimises the performance, reliability, and lifespan of winding wire for your specific application. Consulting an experienced enamelled winding wire manufacturer will help you select the right enamelled copper wire considering your application’s practical requirements.

GEEKAY – a Global Supplier of Copper Winding Wires with Optimal Temperature Rating

GEEKAY is an established super enamelled copper wire manufacturer in India. We manufacture both round and rectangular enamelled copper wires with different enamel coatings to cater to varied applications. We have a strong R&D team to support customised specifications. Quality is our utmost priority and we ensure that our winding wires meet your requirements.

Contact Us today with your requirement specifications to see the quality advantage.