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Charged EVs | Infinitum Electric brings its PCB stator technology to EV motors

Infinitum Electric says its axial flux motors with printed circuit board stators offer weight reduction, cost reduction and efficiency gains.

Batteries are getting a lot of media coverage these days—they represent a rapidly-developing technology that’s seen as the key to the electrification of transport. Motors, however, are considered a fairly mature technology, and the humble rotor and stator seldom get to be in the spotlight.

Texas-based Infinitum Electric aims to change that. The company’s bold red motors demand attention for their design and performance.

Infinitum Electric says its unique motor design—an axial flux architecture that uses a printed circuit board (PCB) stator—dramatically reduces size and weight, improves efficiency and reliability, and also offers high speed, excellent torque, quieter operation and a modular platform.

Charged recently spoke with Infinitum VP of Business Development Bhavnesh Patel to catch up on what the company is doing, and get a more detailed explanation of what makes Infinitum’s motors different.

Charged: Could you explain the advantages of using a PCB stator? Is it suitable for EV applications? 

Bhavnesh Patel: Every motor or generator has a stator. It typically consists of heavy iron with copper wire wrapped around it. We etch the copper onto a PCB to replace that iron-copper stator. Our motor is equal in performance to a conventional motor with a third less copper and absolutely zero iron. This results in a much smaller, lighter electric motor. 

We etch the copper onto a PCB to replace that iron-copper stator. 

A traditional cylindrical motor type is a radial flux motor. Our equivalent is an axial flux motor, which has a much thinner form factor and is a lot simpler to put together. You have a rotor on the bottom, a rotor on the top and then your stator sits in the middle. What we do for our traction motor is stack a couple of these together. We have a 150-kilowatt machine that we’re working on right now. It’s a very modular approach—if we have a customer that says, “Hey, I need 200 kilowatts or 300 kilowatts,” we stack multiple modules together. Beyond the modularity, we have a very significant power density advantage, meaning that for the amount of mass we have, we can put a lot more power through it. And we ultimately make the vehicle a lot lighter and more efficient.

Charged: Why do you stack modules? 

Bhavnesh Patel: There are a couple of reasons why we choose to stack it. One is that, with an axial flux technology, as the torque in the application goes up, the diameter increases. In order to constrain the diameter, we can stack multiple modules. We could do a 100-kilowatt motor with one stator—it would just be wider. For a passenger vehicle, for example, that might not be feasible, but a truck application absolutely could be feasible. It depends on the application. We’ve stacked modules, we’ve done single-stator—both are very feasible.

Charged: How do you achieve a third less copper usage?

Bhavnesh Patel: The surface ratio of a PCB stator vs a copper wire-wound stator is greater, which allows for more effective cooling. Thermal dissipation is the constraint in running additional current through copper. A larger surface ratio allows for higher thermal dissipation and as such, less copper is required. This is a fundamental physical property. In a conventional liquid-cooled traction motor, two approaches are typically utilized—a water jacket integrated into the motor housing, which cools the iron stator and fluid across the copper winding end-turns. In both approaches, the cooling is not being directly applied to all sources of heat. 

The liquid-cooling approach we’ve taken is different. We essentially hollowed out the shaft on the motor and inserted nozzles that spray the fluid across the surface of the entire stator. We’re getting the fluid directly on the heat source, and can more effectively remove heat from the motor. One of the limitations in how much current you can run through a stator, whether it’s ours or anybody else’s, is how hot it gets. And because we’re more efficient at removing heat, we can run a lot more current through it. Typically, with an air-cooled radial flux motor, your current density is in the range of 3-4 amps per square millimeter (3,000 amps per square inch). With our liquid-cooled PCB stator, we can run 42-56 amps per square millimeter (27,000-36,000 amps per square inch), so it’s orders of magnitude greater.

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