Protecting EV motors more efficiently

As electric vehicle (EV) technology advances to improve vehicle performance and range, battery technology may be grabbing many of the headlines, but equally important are the electric motors that convert battery energy to vehicle propulsion. For many years, one type of EV motor called a permanent magnet motor (PMM) has incorporated a carbon fiber-reinforced thermoset sleeve that wraps around the PMM’s rotor. The sleeve keeps the rotor assembly from flying apart at high rotational speeds. In a recent advancement, Trelleborg Sealing Solutions (Albany, N.Y., U.S.) has leveraged some advantages of thermoplastic resins to develop an improved design for the sleeve. Increased motor efficiency may soon propel the Trelleborg design into production EV motors.

In the EV market, PMMs have recently been selected for several production vehicles over the more common induction motor. These include the Tesla Model 3 and the Chevrolet Bolt and Volt. Induction motors feature a relatively low cost and high reliability, but PMMs offer higher power density and lighter weight. The price of PMMs is a decided disadvantage, due to the high cost of permanent magnets — most commonly made of rare earth metals. Therefore, every advancement that increases the efficiency of these motors is critical to building a business case for them. This is why Trelleborg’s carbon fiber-reinforced thermoplastic (CFRTP) sleeve for PMMs is under serious consideration for the EV market.

“We have built a couple sleeves for evaluation in this market, though we can’t elaborate at this time,” Trelleborg product manager, Reid Hislop reports. But commercial application to the EV market seems likely on the near horizon. Trelleborg’s proven composite design and manufacturing technology have already been incorporated into PMMs for other commercial applications, such as industrial pumps and drives for machine tools, down-hole oil and gas pumps, and HVAC equipment.

Powering EVs
EV motors operate through electromagnetic forces. A rotating magnetic field is produced in the stationary component, the stator, by applying an alternating electric current. The stator surrounds the rotating component — the rotor — which is also magnetized. The resulting magnetic attraction and repulsion between the two components forces the rotor to rotate and power the drivetrain.

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