In the EV revolution, one of the most fascinating challenges is to ensure proper thermal management and electrical insulation of motors, batteries, and other key components.

During last years and always in contact with R&D division of premium automotive customers, Politubes has engineered a revolutionary and already hyper-validated  solution to improve stator slot thermal management & insulation of electric motors (EV & HEV), which use copper hairpins, I-Pins, Wave-Windings or S-Winindings.

Copper hairpins guarantee better performance in terms of efficiency, power density, cost, acoustic impact and are in line with the latest technological developments in the E-Mobility industry, particularly with reference to EV traction motors.

For the insulation of stator slots with hairpin windings, Politubes suggests the use of custom-designed spiral wound EV-Tubes produced only with the best insulation films available as NKN (Nomex /Kapton /Nomex) – NMN (Nomex /Mylar /Nomex) – Nomex 410 – Nomex 864 – Nomex 818 etc.

EV-Tubes tubes are thinner than traditional insulation tapes and are supplied with thicknesses of only between 0.10 and 0.25 mm without overlap.

The reduction in thickness and the absence of insulating film overlap within the slot guarantees a dramatic improvement in the following macro-areas:

THERMAL MANAGEMENT

• The thermal conductivity within the stator slot improved dramatically due to the reduced thickness of the EV-Tubes, which are produced without overlaps. Actually, the overlapped area of traditional insulation tapes is one of the areas where the highest temperatures can be achieved;
• Overheating can reduce motor efficiency, deteriorate key components, and reduce the resistance of electrical insulation. However, improved heat dissipation can translate into a positive impact on all vital matrix and motor lifetime;
• Reduction of dangerous heat peaks that can damage the magnetic flux of the rotors’ permanent magnets over time;
• UL system integration up to 220°C.

INSULATION & REDUCTION OF PARTIAL DISCHARGES

• Reduction of partial discharges (PD) thanks to hermetic tube closure;
• The hermetic tube closure provides a much higher level of electrical insulation than conventional films, where the overlapped area remains the weakest part in the insulation chain;
• Reduced risk of insulation displacement caused by micro-vibrations during motor lifetime and that can cause partial discharges (PD);
• Improved uniformity, thermal, dielectric and chemical insulation inside stator slot;
• Dielectric strength up to 12 kV;
• Excellent impregnation properties with traditional resins.

COPPER FILLING FACTOR, PERFORMANCE AND MOTOR LIFE

• The insulator thickness reduction thanks to the lower thickness and absence of overlaps, makes it possible to improve copper filling factor inside the stator slot with consequent optimization of torque and improved motor performance;
• The reduction of heat peaks and partial discharges guarantee longer motor life.

HANDLING, MECHANICAL PROPERTIES, WASTE REDUCTION & SUSTAINABILITY

• EV-Tubes easily take on the rectangular shape of haiprin, ensuring excellent adhesion;
• The use of EV-Tubes improves the productivity of winding process of the stators because insulating tape cutting and shaping steps are omitted;
• The absence of overlaps reduces the risk of telescopic jamming when inserting hairpins into the slots, reducing scrap and increasing productivity;
• Reduction accidental cases where the insulation tape is pushed out of the slot during hairpin insertion;
• Reduction of the risk of displacement of the insulation when curving the hairpin;
• Superior mechanical tensile strength.

EV-Tubes tubes are custom-designed for 400V, 800V and even more motors.

For > 800V motors we recommend the use of special grades Nomex (818 – 864) and Kapton MT+ with state-of-the-art dielectric, heat dissipation, flame resistance and durability performances.

NKN insulating spiral wound tubes can be formed inside the slot or can be easily inserted onto copper bars taking the rectangular shape of hairpins.

World-leading companies in process automation already offer fully automatic systems for inserting EV-Tubes tubes into stator slots.

For automotive applications, Politubes also supplies ultrasonically welded caps made from a combination of Nomex 411 and heat-shrinkable polyester used for insulating joints, motor cable terminations, and other components ensuring uniform insulation throughout the system.

(Nomex and Kapton are DuPont registered trademarks)