Traditionally, motor laminations are welded together down the side of the stack for structural integrity. This is typically achieved by MIG welding, TIG welding, or laser welding. However, the weld itself is the source of inter-laminar cross-circuit shorting which results in eddy current loss and increased heat. For electrical vehicle applications, efficiency is king and motor designs require a better process for holding the laminations together that eliminate as much loss as possible.
The best alternative to welding the stack is to bond laminations. Bonding reduces both inter-laminar loss and corrosion. Additional benefits of bonding laminations include improved thermal conductivity, reduced noise from hum and greater resistance to higher temperatures.
The bonding process of laminations is fairly straightforward. After laminations are stamped or laser cut, the bonding adhesive is applied via a roll coating process or dip tank process then cured to a class B stage. Once laminations have cooled and are able to be handled, they are stacked into custom fixtures that are precisely compressed. The stacked fixtures go back into a furnace and are heated again for a specific period of time until the bonding agent reaches its final Class C stage for maximum strength.
Some additional benefits of bonding laminations include:
- The bonding agent acts as both as an insulator and bonding adhesive
- Flexibility in design - design without limitations for ideal motor engineering since positions for weld seams do not have to be taken into account which leads to more efficient motor design
- Accurate dimensions and mechanical stability - high tolerances with optimal shape stability can be achieved because bonding eliminates lamination expansion from the high heat of seam welding
- Optimal thermal conductivity - narrow tolerances on lamination stacks improves heat dissipation which in turn reduces cooling needs, cost and overall weight
- Improved acoustics - bonding dampens vibrations which in turn results in reduced noise and hum