Bench Talk

Connecting Sensors for Oil-Cooled Motors in Electric Vehicles

(Source: AhmadTriwahyuutomo / stock.adobe.com; generated with AI)

Electric vehicles (EVs) are becoming more common on our streets. While passenger vehicles receive the most headlines, the development of electric alternatives to internal combustion is taking place in every sector of the transportation industry, from small personal mobility devices to the largest commercial vehicles.

EVs do not use combustion to create power; however, they still generate heat. The electric motors that drive the latest EVs deliver impressive performance, but even the most efficient device will produce excess thermal energy due to the electrical resistance of the conductive components. Whenever electric current flows through such a component, a proportion of the energy will be lost as heat.

Therefore, heat is an unwanted byproduct of EVs and must be managed. Many motors use copper wire, taking advantage of its strength and conductivity to create efficient motors. Still, elevated temperatures cause an increase in electrical resistance within copper wires. This makes the motor less efficient as more electrical energy is lost to heating. In this blog, we’ll take a closer look at a new solution to cooling EV motors.

Cool Motors Are More Efficient

Keeping the motor cool allows for more efficient use of energy. In the case of electric vehicles, this improved efficiency translates into increased range. So-called “range anxiety” is one of the critical psychological hurdles that EV manufacturers must overcome when encouraging drivers to adopt this new technology. The cooling of electric motors within EVs not only provides a direct benefit by improving efficiency, but also provides an indirect effect on public perception by creating more capable EVs that are viable alternatives to established technologies. For this and other reasons, thermal management is crucial to EV development.

Heat also hurts overall reliability. Materials deteriorate quickly at higher temperatures, causing issues that range from the oxidization of metals to the softening and deforming of plastic. Keeping these materials cool will prolong the motor's life and improve the overall reliability of EVs.

Thermal management is, therefore, critical to EV efficiency and long-term safety. A cooling system for electric motors creates a more efficient and reliable vehicle and improves overall safety by reducing the dangers of unwanted hotspots.

A Cooling Solution

Designers are tackling the challenge of thermal management with liquid cooling. Conventional vehicles solve this problem by using water-filled radiators to dissipate heat created by the combustion of fuel. However, this is not a practical solution for electric vehicles for several reasons. First, the engine in a conventional vehicle is centrally located in an engine bay, providing sufficient space for the efficient transfer of water to provide cooling. In contrast, the electric motors within an EV are usually placed in line with the axles. Handling heat within the motor is easier than providing complex plumbing that links to a central radiator.

It is also necessary to use a liquid other than water. The conductive nature of all but the purest water means that mixing it with electricity creates a range of new hazards. As a result, designers are turning to oil to provide the necessary cooling.

The cooling of an electric motor uses a sealed housing or case. The case is not entirely filled with oil, as this would create an enormous amount of drag on the moving elements of the motor. Instead, oil is pumped through the central shaft of the rotor or sprayed at the rotating windings. The oil then carries the heat away from the motor, to be collected in a sump for cooling and then circulated again. The sealed housing prevents oil leaks.

Designers need electrical access to the housing to provide connections for resolver/transformer sensors and negative temperature coefficient (NTC) sensors that monitor the condition of the motor. To meet this need, Molex has developed the MX150 Pass-Through Sealed Connector to provide such a connection (Figure 1). It is derived from the proven MX150 connector system to create a rugged oil-resistant connection for signal wiring into oil-cooled motors.

Figure 1: Molex MX150 Pass-Through Sealed Connectors utilize the rugged and field-tested MX150 connector design to provide an oil-resistant connection for signal wiring to the inside of oil-cooled motors, enabling the next generation of high-performance electric motors.(Source: Mouser Electronics)

The MX150 Pass-Through Connector is fitted with a two-ring seal to ensure improved reliability when compared to single-ring seals employed by other connectors. It is sealed to IP6K9K and is available in a 12-circuit, two-row configuration, fitted with 1.50mm terminals that can deliver 14V_DC maximum voltage and current up to 12 Amps.

The increasing role of oil-cooling within motors, batteries, and even power electronics means that designers require secure, oil-resistant solutions to provide the all-important connection with sensors. The tried and trusted Molex MX150 family is now available as a pass-through sealed connector to help create the efficient electric vehicles demanded by tomorrow’s customers.

Conclusion

As EVs evolve, efficient thermal management will continue to be important to optimize performance, safety, and reliability. Oil cooling is on the rise as a dominant solution, particularly for motors, batteries, and power electronics, offering better efficiency and lifespan for EVs. Designers are faced with creating reliable connections for essential sensors within these oil-cooled systems. Molex’s MX150 Pass-Through Sealed Connector delivers a robust and oil-resistant solution so that EVs can meet the demands of today’s consumers and prepare the transportation industry for a more sustainable future.

Author

David Pike is well known across the interconnect industry for his passion and general geekiness. His online name is Connector Geek.