Electric Vehicles Come of Age
High Temperatures: Not a Problem for Silicones
ZF Sachs electric motors boast a high power density thanks to optimal motor design and a special rotor and stator construction. For the rotor, the company uses very strong permanent magnets made from a neodymium-iron-boron sintered material. The magnets are bonded to sheet metal laminates that have already been pressed into the metal rotor arm. The stator is notable for the uniform, tight winding of the copper coils. All these features together yield a compact design capable of delivering the desired electric power density.
„We decided to use silicones from WACKER. The deciding factors were WACKER’s extensive range of products, good technical support and the consistently high quality.“
Naturally, high power densities create high temperatures inside the electric motor. Temperatures can reach 200 °C, particularly around the currentcarrying stator windings. “These high temperatures necessitate the use of silicone products,” says Kewes.
SEMICOSIL® Ensures Flexible Adhesive Layer
Rotors and stators at ZF Sachs are made in two separate, largely automated lines. Silicone products are applied and heat-cured in each. The rotor line utilizes SEMICOSIL® 988, a silicone adhesive, to bond the permanent magnets in place. It produces a flexible layer of adhesive which accommodates thermal expansion and contraction of the bonded parts without tearing.
ELASTOSIL® and SILRES® Keep out Moisture
In the stator line, the annular area containing the electrical contacts of the windings is encapsulated in ELASTOSIL® RT 705 silicone rubber while the rotor windings areimpregnated with SILRES® H62C silicone resin. These two steps provide the motor with perfect moisture and water protection, ensuring that it stays permanently safe and reliable: “The motor won’t even short-circuit when dipped in salt water – it simply keeps on working,” adds Kewes.