Posts By: Jeffrey Jenkins

A closer look at power factor correction

Power Factor Correction (PFC) used to be something that electronics manufacturers only grudgingly added to a product – usually because of complaints about breakers tripping prematurely, or to meet regulatory requirements in the EU – but these days PFC is showing up in more and more products. While one should never underestimate the ability of… Read more »

A closer look at rare earth permanent magnets

Rare earth magnets have gotten a lot of coverage in the EV press over the years for being expensive – especially back in 2011 when a supply disruption in China sent the prices up anywhere from fivefold for neodymium to 20-fold for dysprosium over the course of a few months – yet they are still… Read more »

The technical reasons Tesla would limit supercharging speed, and other practical charging considerations

Recently, a bit of a kerfuffle kicked up when a Tesla Model S owner noticed that the maximum charge rate for his car on the Supercharger network had suddenly been cut from 120 kW down to 90 kW, apparently the result of too many fast charge cycles. Tesla’s explanation was, essentially, that many things can… Read more »

EV tech explained: What are the limiting factors of an EV’s regenerative braking force?

In many EVs, regenerative braking is limited by the manufacturer to a modest level, and usually offers little or no ability for the driver to adjust it (aside from the few cases in which regen is made proportional to the initial movement of the brake pedal). Is tepid regen braking the result of some sort… Read more »

EV tech explained: Why do EVs restrict the amount of battery capacity that can be used for driving?

All EVs that use lithium-ion batteries are designed so that their full capacity can’t be used in driving – a few kWh are always left over as a buffer. Sometimes you’ll find this figure in spec sheets, which might (for example) quote capacity as “60 kWh (55 usable)” or some such. What is the reason… Read more »

A closer look at the semiconductor switch

In this article I’ll be giving an overview of that most important of power electronics components: the semiconductor switch. I’ll first address what a switch is, and then delve into some of the more important compromises and shortcomings that exist in real-world switches that engineers must contend with when designing chargers, motor controllers, DC-DC converters… Read more »

A closer look at back electromotive force

Why motors generate and generators motor In a previous article I took a closer look at regenerative braking, and mentioned an old engineering saying that every motor is a generator and every generator is a motor (along with the caveat that some are more suited to the opposite purpose than others). This time around I’ll… Read more »

A closer look at switched reluctance motors

The electronically-switched reluctance motor – often shortened to the switched reluctance motor, or SRM – has been gaining in popularity over the last decade because it is simple, robust, and arguably the least expensive of all motor types to manufacture. The reasons for the relatively late blooming of the SRM – the first reluctance motor… Read more »