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Posts By: Jeffrey Jenkins

Power electronics thermal limits and how to not exceed them

To someone who isn’t involved in power electronics design, it might seem unreal that the amount of power a component can handle depends more on how effectively waste heat can be removed from it than it does on the specific electrical ratings. Sure, the voltage and current ratings are important (especially the voltage rating), but… Read more »

A closer look at brushed AC motors in EVs

Everything old is new again: BMW’s fifth-generation eDrive features a wound-field synchronous AC motor Brushed DC (and AC/DC universal) motors are much maligned for a number of reasons, but one of the chief—if, perhaps, somewhat exaggerated—complaints is that the graphite brushes, and the segmented copper commutator they ride on, wear out over time, all the while producing… Read more »

How a motor’s operating speed, torque and control strategy affect its efficiency

Second only to power output, efficiency is one of the most fudgeable ratings that applies to traction motors for EVs (right up there with capacity and cycle life claims for Li-ion batteries…). For common 3-phase industrial AC motors, most of the specmanship shenanigans have been dealt with by NEMA (National Electrical Manufacturers Association), a voluntary… Read more »

A closer look at minimizing charging losses: The charger (Part 2)

In the previous article, we looked at the various losses incurred on the AC side of the circuit while charging an EV’s battery (from the breaker in the load center to the EVSE inlet on the EV), as well as things that could be done to minimize them, either by the OEM, the electrical contractor… Read more »

A closer look at minimizing AC charging losses: From the breaker to EV (Part 1)

It’s fairly well known by now that EVs cost far less per mile to drive than their closest ICE counterparts, and the main reason is simply that the EV drivetrain is far more efficient at converting its stored form of energy into motion. In the quest to improve efficiency even more, the focus tends to… Read more »

A closer look at why heat pumps are dominating EV HVAC systems

Heating or cooling the interior cabin of an EV substantially affects the vehicle’s on-road efficiency, and the HVAC system often gets the proverbial “rented mule” treatment. In an ICE vehicle—particularly an underpowered one—there is a visceral reminder that running the AC, at least, costs something, since there is a palpable hit to acceleration whenever the… Read more »

A closer look at humidity control methods for EV electronics

It’s a well-known trope that water and electricity don’t mix, but keeping the two separated is often deceptively difficult, because the simple solution of just sealing the box is insufficient on its own. This is because of condensation, which can come from water vapor in the air at the time the box was sealed, or… Read more »

A closer look at axial flux motors

In Issue 49, we reviewed some of the more promising advancements in materials and construction techniques for EV traction motors, one of which—the axial flux design—will be the focus of this article. Despite being characterized as an advanced construction technique, the axial flux design is actually one of the oldest ways of constructing a motor—it’s… Read more »

High-voltage EV battery packs: benefits and challenges. More voltage, more better?

In 2020, Porsche delivered just over 20,000 units of its luxury Taycan EV—the first vehicle from a major automaker to sport an 800 V (nominal) battery, which is more than double the voltage of its competitors (and firmly into light-rail and switchyard locomotive territory, actually). It appears that many other EVs will soon follow in… Read more »

Isolation technologies for EV power electronics

A previous article on bidirectional chargers touched on using transformers to provide isolation at high power levels—in which application they are the only game in town, really—but this time the focus will be on achieving isolation at low power levels, such as the feedback signal in a regulator, data communication buses between devices, gate drivers… Read more »