EV Tubes are a hyper-validated insulating solution for stator slot liner that are using copper hairpin, I-Pin, Wave Winding, S-Winding. EV Tubes are custom-designed multilayer spiral tubing produced without layers overlap in the slot closing area. They are designed with a low thickness and using the most selected and well known insulating material available.

Reduced thickness and no overlap of insulating film inside the slot means significant improvement in the following macro areas:


EV Tubes improve thermal conductivity within the stator slot due to their reduced thickness and the absence of closing overlaps like. The overlapped area of traditional insulating tape can retain heat causing dangerous heat peaks that can damage some vital motor components such as permanent rotor magnets over time.

The improved heat conductivity can be conversely translated into a positive impact on all vital matrix by preventing motor overheating and the consequent reduction in the efficiency and durability of electrical insulation.


EV Tubes provide hermetic closure of the insulation inside the slot with a dramatic improvement of the electrical insulation compared to conventional insulation tapes, in which the overlapped area still remains open and it is the weak element in the insulation chain.

The mix of thermal management and hermetic closure of EV Tubes inside the slot avoid deterioration of the insulation performance, leading to a reduction of heat peak, partial discharges (PD) and extend motor life.

The resistance over time to partial discharges also occurs due to the reduction of the risks of displacement of EV tubes compared to conventional insulation tapes that could be caused:

  • During the bending phase of hairpins;
  • By micro-vibrations during normal motor life.

Conversely EV Tubes remain stably closed, displacement-free and hermetically sealed.

EV Tubes are suggested for motors of 400, 800 V and above providing excellent impregnation properties as well.


EV Tubes also optimize the copper filling factor inside thanks to the reduction of insulation thickness inside the slot due to the absence of overlaps. The consequence is optimization of torque and overall improvement of motor performance.


The absence of overlap and the optimization of the EV Tubes slot filling factor, reduce the risk of jamming or telescoping effect when inserting hairpins into the slot decreasing costly scrap, line blockage and increasing productivity.

For massive productions, Politubes suggest the use of automatic machine for inserting EV Tubes inside stator slots.

This machine has been designed through a partnership with HOMA Machine Automation srl and in addition to all the technical advantages outlined above, we can now support our customers with the automation of the process of inserting EV Tubes into the slots.

This station for automatic insertion of EV Tubes can be easily introduced without major modifications to existing production lines. By inserting EV Tubes in an automatic way, the winding productivity of the stators can be improved as well because cutting and shaping steps of insulating tapes can be removed.

Thanks to elastic memory, EV Tubes perfectly take the shape of the slot by adhering to the wall perimeter.

The use of EV Tubes is also an answer to the problems mentioned below:

  • It is well known that the simultaneous insertion of hundreds of hairpins into the stator is one of the most delicate steps during motor assembly and is also one of the main causes of production waste because this operation can be affected by the slot shape, tolerances of the hairpins and the shape of the slot insulator.
  • The reduced slot filling capacity of conventional insulation tapes (due to overlap) together with excessive pressure during hairpin insertion can damage the insulator itself. The problem is that in this case it is difficult to diagnose the damage on the insulator after hairpin insertion. In the worst cases, the slot insulator itself could be pushed out of the slot due to hairpin pressure in the overlapped area.
  • The expansion of the paper insulator (coining) on the hairpin insertion side helps to fit into the hairpin legs, but the paper overlap is not easy to manage in the expanded area. Hairpins may snag right in the overlapped area creating a telescoping effect of the insulator or worse the insulator could even be pushed out of the slot.
  • In stator packs longer than 100 mm, inserting the paper insulator is not easy because the paper could twist along its length, changing the shape of the paper.


EV Tubes improves sustainability because less insulation material is used by taking away the tape overlap inside the slot and because of the reduction of production waste.

For automotive applications, Politubes also supplies ultrasonically welded insulator caps produced with used for insulation of joints, motor winding terminations, and to other components ensuring uniformity of insulation to all the system.

Politubes is IATF 16949:2016 certified by TÜV Rheinland®

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