For the last decade, electric vehicle engineers have faced a difficult choice when building traction inverters - the device that converts DC power from your battery into AC power for your motors. They could pick either Silicon (Si) IGBTs, which are cheap, indestructible, but inefficient; or Silicon Carbide (SiC) MOSFETs, which are incredibly efficient, but fragile and expensive.
Most premium EVs today, including the Model 3 and Model Y, use SiC MOSFETs to maximize range, but that efficiency comes at a price, driving up motor costs.
Tesla’s new patent application (WO 2026/010828-A1), titled “Hybrid Traction Inverters for Electric Traction Motors,” proposes a third way: putting both chips in the same box, and actively switching between them in real time.
Variable Transmission
The core innovation described in the patent is a controller that operates like an automatic transmission, shifting the electrical load to the chip best suited to the current driving condition.
The cruising gear would be the SiC MOSFETs. When you are steadily driving on the highway, efficiency is everything. The patent describes a low-current mode in which the controller prioritizes these MOSFETs and keeps them active, maximizing range.
The other gear would be the power gear, with the Si IGBTs. When you floor the accelerator or tow a heavy load, raw durability matters more than efficiency. In these high-current scenarios, the system shifts priority to the Si IGBTs. These rugged chips turn on first to absorb the heavy electrical hit, thereby protecting the more delicate SiC chips.
Cutting Costs
While the performance and efficiency benefits are clear, the primary motivator behind many of Tesla’s innovations is cost, and this is no exception. Silicon Carbide chips can cost significantly more than their silicon counterparts.
Tesla’s patent goes on to describe a physical layout that uses a 2:1 ratio: two cheap Si IGBTs for every expensive SiC chip. This allows Tesla to downsize the expensive SiC component. Instead of sizing up the SiC chips to handle the Model S Plaid’s peak acceleration (which is a 1% use case), they only need to size them for highway cruising (a 99% use case). The inexpensive IGBTs can handle the high-current loads required for launching from a standstill.
This next-gen powertrain is significantly cheaper to build and delivers nearly the same range as a full-SiC system.
Increased Durability and Backup
However, cost isn’t everything. What’s interesting is how Tesla intends to handle safety. Permanent Magnet (PM) motors, like those in the Model 3 and Model Y, generate Back EMF — a voltage spike that shoots back into the inverter if the motor spins too fast. This can happen if the system crashes or if the vehicle is towed with the PM motor wheels on the ground.
Tesla’s design uses cheaper, more resilient IGBTs as a bodyguard. A fault management circuit can instantly override the standard efficiency-first driving logic if a dangerous voltage spike or fault is detected. That ensures these heavy-duty chips handle the load before the more delicate SiC chips, protecting them and keeping your vehicle on the road.
The Technical View
For the engineering-focused, the patent also outlines just how Tesla manages to get these two competing technologies to work together without fighting each other.
The key here is the timing envelope. The SiC MOSFETs and Si IGBTs cannot be turned on at the same time. Tesla’s key innovation here is a timing protocol that ensures that the rising edge of the IGBT signal leads the SiC signal by 100 nanoseconds to 10 microseconds. That minuscule timing creates a protective envelope in which the Si chip absorbs all the stress.
In addition, to prevent magnetic interference (parasitic inductance), the physical board layout will place the SiC MOSFET directly in the middle, sandwiched between the Si IGBTs. This balances all the electrical fields and prevents interference - essential inside a motor.
What This Means For You
Ultimately, this patent isn’t just about saving Tesla some money on parts - it’s about breaking the compromises that engineers need to make in motor design.
Until now, customers have generally had to choose between Range, Performance, or Affordability. You could pick two - the third part of the triangle just wasn’t obtainable. High-range, high-performance cars like the Model S are expensive because they require massive amounts of silicon carbide.
Meanwhile, affordable vehicles had to sacrifice either range (smaller batteries) or efficiency (cheaper Si inverters).
This new hybrid design will allow Tesla to cut that compromise. That means cheaper motors, cheaper EVs, better reliability - and all the same performance that makes every single Tesla a thrill to drive.
