Automotive Engineering - October 2023 - 22

The first modern EV was...
A CORVAIR?
Most industry experts
cite GM's EV1 as the first
EV of contemporary times.
But the EV1 had a pioneering
forerunner from decades prior.
by Larry Mihalko
Started as a
research project in 1963,
GM's Electrovair was in many
technical aspects the predecessor of
GM's better-known EV1 - and most current EVs .
T
he production EV1 by General Motors in the 1990's gets some
credit for being, technology-wise, one of the first viable EVs.
The limitation was its heavy lead-acid battery storage and
short range. Less known is the fact that in 1963, a full quarter
century earlier, GM was working on its first EV that pioneered a stateof-the-art
propulsion system that is still the basis for all EVs today.
General Motors Research and Engineering staff
General Motors' research into a new generation of EVs began at the
vehicle level in 1963. The company's goal was to build an EV that
would work in the automotive environment of that time - which is
strikingly similar to the environment today. GM engineers focused
mainly on the propulsion system and concluded from hardware
bench-testing that a 3-phase induction motor was the best choice. It
was understood that no battery technology yet existed that could
provide the range and durability needed commercially.
Engineers wanted to install the propulsion system in an existing vehicle;
given the vehicle lineup available, the choice was obvious. The
Corvair was seemed almost designed to be electric, as it was the lightest
vehicle at GM thanks to its small size and unibody design. The rearmounted
6-cyl. engine and transmission were in line with the rear drive
axle. This made it easy to substitute an electric motor and gear drive.
The EV they developed was named the Electrovair in tribute to its
Corvair roots.
Electrovair engineering
Variable Frequency Drive: The chief enabler for the Electrovair, and all
EVs today, was the invention of what is called a Variable Frequency
22 October 2023
Drive (VFD), more commonly called an inverter. The VFD
could take DC from a battery and turn it into AC of any
frequency. This inverter was possible thanks to the invention
of semiconductor solid-state devices in the 1950s.
These devices - " transistors " - have had as profound an
impact on our lives as perhaps anything since the wheel.
The VFD is what finally removed the main limitation
of AC motors for automotive propulsion, as adjusting
motor speed had not been realistically possible before
then. Until then, AC motors had reliably trudged along
for 70 years, a massive army that powered the world
at the speed set by the power grid. Motors now were
free to roam the streets.
The solid-state semiconductors used in the Electrovair
are conceptually quite simple. They are called silicon-controlled
rectifiers (SCR) and were invented in 1958. They
essentially are an electronic on-off switch that can allow
or prevent the flow of large amounts of current as commanded
by a very low-voltage signal created by a logic
circuit. These switches can be combined to convert the
battery's DC into an AC that is fed to the motor's electromagnets
to control motor speed and torque. They switch
very quickly, enabling high-frequency signals to achieve
high motor speeds. The EVs of today use much more capable
semiconductor switches, but the basic principles of
" chopping up " DC to make AC is still at work.
AC induction Motor: The induction motor and its
gearbox were compact. The motor produced a peak
115 hp and had a maximum speed of 13,000 rpm. This
AUTOMOTIVE ENGINEERING
GM HERITAGE CENTER
Automotive Engineering - October 2023

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