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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 . (GM Heritage Center)

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.

The 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 state-of-the-art propulsion system that is still the basis for all EVs today. Here is that story.

Electric vehicles have been around since the birth of automobiles. In the early years (1900-1920) when all powered-vehicle invention was starting from zero, electric was a somewhat competitive alternative to the internal-combustion engine. It provided good, normal low-speed urban transportation. With most EVs there was no need for the difficult task of crank-starting like with an ICE vehicle. Henry Ford’s wife Clara famously drove a Detroit Electric Car in the 1910s.

The EV competition did not last long. Internal-combustion engine power and capability increased quickly, electric starters for IC engines appeared in 1912, manufacturing volumes increased and prices for vehicles such as the Model T plummeted. Electric technology did not have a similar rapid advance in capability and there was little motivation to pursue one, since the future clearly was IC engines. Electrics were pretty much gone by 1920, with a few exceptions lingering at low volumes. There was no serious consideration of them commercially for the next 40 years.

In the 1950’s, smog-related health problems in the Los Angeles basin became so severe that citizens demanded action to reduce air pollution. Research determined that smog was caused by sunlight-induced reactions of hydrocarbon and nitrogen oxide emissions — and Los Angeles was a witch’s caldron of stagnate atmosphere that provided the perfect place for making it.

None other than Ronald Regan — then Governor of California – signed into law the California Air Resources Board to regulate air quality. The automobile was a big contributor to the problem, and work began on emissions controls for IC vehicles. The first was PCV (Positive Crankcase Ventilation), which reduced emissions by 50%. Many other pollution-mitigating technologies followed.

In 1960, it was clear that legislation to regulate automotive air pollution was coming. Manufacturers began to look at alternative propulsion systems — electric being the most obvious. The timing was fortunate: several new solid-state electronic technologies had been invented that would become the enabler of the next generation of EV propulsion.

Electric-motor primer
To understand the modern electric vehicle and why it is possible, it helps to understand electric motors. There are two basic kinds: Direct Current (DC) and Alternating Current (AC).

The original electric vehicles in 1900 were all DC motors because those worked with available batteries and used the simple speed controls of that era. Batteries provide a constant voltage that is “steady” with the flow of electrons always in the same direction from the battery into the circuit. A DC motor often uses both electromagnets and permanent magnets. The electromagnets have their magnetic forces switched mechanically as they turn so that the magnets attract and repel in a choreography that makes the motor spin and do work.

DC motors can be easily controlled, with a speed determined by the voltage applied. The mechanism for controlling that can be a simple variable resistor that acts like a throttle. This was all available in 1900 and earlier. The downside of DC motors is that to fulfil typical automotive-propulsion requirements, they must be relatively large and heavy. They also have mechanical parts that wear out (sliding electrical contacts called “brushes”), their speeds are limited because of the mechanical switching and they can be more complicated to manufacture.

AC motors (induction motors were the original ones) were invented by Nikola Tesla in 1888 and have since become the backbone of mechanical power for our manufacturing facilities and the overall industrial revolution. As the name implies, an alternating current will switch the direction of the flow of electrons back and forth in the circuit. This back-and-forth motion occurs at the frequency of the power supply. In fact, the design of the U.S. power grid — the 60 HZ alternating frequency, the three separate phases of alternating current available in industrial settings, the 120 volt per phase — was directly influenced by Tesla and George Westinghouse to optimize the use of AC induction motors.

Induction motors are deceptively simple in appearance and seem to work by magic. It is a tribute to the genius of Tesla that he was able to visualize how alternating current could create magnetic fields in the motor to cause rotation and useful work. Many EVs today have moved beyond the original induction motors and use what is called a synchronous permanent-magnet reluctance motor.

The advantage of AC motors is that they can have a reasonable size and weight at automotive power requirements, they are relatively simple to build, they can spin really fast and they are efficient. The major disadvantage is that they were traditionally a constant-speed machine with RPM tied to the alternating frequency of the power supply — the power grid in manufacturing applications. Any simple AC motors, such as some that still may be operating in homes, run at constant speeds that are multiples of 60, the grid frequency; 3600 RPM is very common.

Continuously variable speed and power in an AC motor, clearly a requirement for automotive applications, was not realistically possible until the late 1950s. This is where the story of the Electrovair begins.

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. Acceleration performance, speed capability and precise speed control for urban stop-and-go driving all were part of the design requirements. The electrification hardware would have to fit into a conventional-sized vehicle with normal passenger capacity. 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 rear-mounted 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. Contemporary EVs put the motor in line with the drive wheels in a similar fashion and AC electric motors — then and now — are reasonably compact compared to an IC engine/transmission of similar power.

The EV they developed was named the Electrovair in tribute to its Corvair roots.

The chief enabler for the Electrovair and all EVs today was the invention of what is called a Variable Frequency 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. We’re not talking about smartphone microprocessor chips. 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.

In the early 1960s, the VFD was in creation/invention mode and the Electrovair absolutely was at the leading edge to explore its practical applications. Electrovair provided the basics of an efficient propulsion system but lacked a viable onboard energy source. The industry would have to wait another 40 years for the next EV breakthrough: automotive-grade lithium-ion batteries.

Electrovair engineering
The drawing below shows the general layout of the Electrovair. Details about the major components shown in the drawing:

  • 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 high-speed capability meant that no transmission with multiple gears was required — the motor drives the wheels directly through a gear-reduction differential. It weighed just 130 lb. (59 kg). The motor alone weighed 1.1 lb. (0.5 kg) per peak horsepower. With the weight of the control system added, it is 1.7 lb. (0.8 kg) per peak horsepower. By comparison, a DC motor of similar power at this time would have weighed between 8 to 15 lb. (3.6 to 6.8 kg) per peak horsepower, more than five times as heavy. The Electrovair’s AC motor had oil cooling for both the rotor and the stator. The motor was made by the Delco Products Division of GM.
  • DC to AC inverter: The inverter is the device that used SCR switches to convert the batteries’ constant DC current into AC. It is a key part of the VFD. The SCR characteristic that enabled the Electrovair was its high electrical capacity, which the motors needed to make automotive levels of power. At the time, the best available were 400 amp at 1200 volts, which was sufficient for the job. The inverter creates three different and independent AC waveforms that are 120 degrees apart in their switching points — they do not occur simultaneously; they are “phased” or shifted in time with respect to each other. That is EV motor descriptions — even for the latest and greatest ones today — talk about a “3-phase AC motor.” The three alternating current phases are applied to electromagnets organized in the motor in a way that creates a rotating magnetic field that ultimately causes the motor to spin. The frequency is controlled to change the speed of the motor. In addition to creating the basic 3-phase and its frequency, the inverter could “modulate” the voltage of the AC power. This modulation changes the peak voltage and thus controls the motor output. It did this with Pulse Width Modulation (PWM) which has become a key technique also applied to today’s EVs. This technology was being invented as the Electrovair was being built.
  • Logic and inverter controls: The SCR switches (18 total, six per phase) in the inverter are connected in a way that switches the battery DC on and off and changes its direction to create the AC output. They need to be controlled and coordinated precisely. The switches need to be timed with respect to each other, for each phase that is created and to the speed and desired speed of the motor. The logic and inverter controls provide the low-voltage control signals to do this. These low-voltage signals are applied to the “gate” terminal of the SCR. The gate is like a ceiling-light wall switch – you and your finger are the logic circuit with control input, the high-voltage part of the switch circuit that is in the walls and lights up the bulb resembles what is going to the motor. Imagine flicking the switch 60 times a second. In addition, the controls are used to adjust the voltage going to the motor, which in turn controls its output torque. When an EV is in motion, the motor speed — and the torque and power it creates — often is changing. The motor controls were connected to a throttle pedal that converted foot-pedal position into a request to the motor controls. The Electrovair was designed so the driving experience was similar to the feel and response of a conventional ICE vehicle.
  • Powertrain cooling systems: IC-engine vehicles have a lot of cooling needs, thus the radiator and fans and other thermal-management components. Electric vehicles also have components that must be cooled to control the temperatures to optimal levels. Heat is the destroyer of things when material limits are exceeded. The Electrovair operated at very high voltages and currents to create the motor power needed to provide performance similar to conventional vehicles. This is just the reality of physics. All the parts in the electrical circuits have some amount of resistance to the flow of electricity — and that resistance consumes energy and turns it into heat. Even low resistance makes a lot of heat at high motor currents. The Electrovair circulated cool oil around the electrical components to absorb the heat. The oil then went into radiators to dissipate the heat to the atmosphere and recirculated the cooled oil back in a continuous flow. The EVs of today face similar challenges to manage the heat created by the high currents and voltages. In addition, lithium-ion batteries get hot when being discharged or charged — and the quicker that happens, the hotter they get. If not controlled, this hurts the life of the battery. Or worse.
  • Batteries:  The battery pack in the Electrovair was made from state-of-the-art space-program technology: silver-zinc chemistry. These were the best batteries available at that time in terms of the size and weight ratio to the amount of energy stored. It was understood that they were not commercially viable because of the cost and the fact that they could be recharged only 60 to 100 times before needing replacement. The Electrovair’s battery pack had 286 silver-zinc cells connected in series. Each cell generated about 2 volts (lithium-ion cells are just shy of 4 volts) and were assembled in 13 trays with 22 cells in each tray. The open circuit voltage of the entire pack was 530V. The basic cell was rated at 60 amp-hours at the 1-hour discharge rate, and on this basis the total energy capacity of the pack was 25.4 kWh. By comparison, today’s EV batteries have capacities that range from around 30 to 200 kWh. The weight of the Electrovair’s battery pack and trays was 680 lb. (308 kg). The battery-pack specifications have similarities to today's EV. Many today are 400-V battery packs, some are 800-V. The voltage determines the maximum power the motors can produce, and Electrovair was in a good place at 530V.

How did the Electrovair perform in comparison to the production 6-cylinder gasoline engine production Corvair? Following are some key metric from the GM report summary as written by the Electrovair creators.

Weight: The curb weight of Electrovair II is 3400 lb. The weight distribution is 38.5% front and 61.5% rear. The power train, including batteries, weighs 1230 lb. The batteries account for 680 lb. of the additional 800 lb. in Electrovair II.

A similar production Corvair weighs 2600 lb. with a 36.5% front and 63.5% rear weight distribution. The production power train weighs 610 lb.

Performance: Electrovair II has the same full power acceleration performance as a high- performance 1966 Corvair with an automatic transmission. Initially, the production Corvair accelerates faster than Electrovair II because our present control system limits the starting torque of the motor. At 20 mph Electrovair II starts to catch up and actually accelerates faster than the production.

Conclusions
The amazing thing about the Electrovair is how advanced it was given the historical context of when it was built. The components it used were very much pioneering the field and all had just emerged from the most advanced research labs in the country.

The basic operating principles used in the Electrovair are essentially the same as those we find in today’s EVs. Tesla Motors used induction motors in some models through 2019 or so. There has been a conversion by most EVs to now use what are called synchronous permanent-magnet reluctance motors. They provide efficiency improvements that enable more driving range, which continues to be among EVs’ biggest challenges. But these new motors still use 3-phase inverter controls.

The challenges that were noted above by the Electrovair creators in 1965 remain today: battery expense, weight and recharging times. Protecting components during inevitable crash events. Cabin cooling and heating. Managing electrical-component temperatures.

These challenges are being solved right now as we enter the EV revolution. The Electrovair gave us a crystal ball view of the future that is today.

Acknowledgements: Some of the information in this article comes SAE technical papers numbered 670175 and 670178, written by GM regarding the project. In addition, photographs and news releases were provided by the GM Heritage Center, with thanks to Larry Kinsel.

Larry Mihalko worked at General Motors for 42 years and held numerous roles in vehicle development at the Milford Proving Ground. He was the Global Vehicle Performance Manager of crossover vehicles for the last 15 years and guided development of the Chevrolet Blazer, Traverse and Equinox, the Buick Enclave and Envision, the GMC Acadia and Terrain, Cadillac XT5 and XT6, Saturn Vue and others during the rapid expansion of the crossover segment. He was involved in the company’s transition to EVs and most recently helped develop its ‘mainstream’ high-volume crossover EVs, the soon-to-be-launched Equinox EV and Blazer EV.

Mihalko currently is involved in launching the Pontiac Transportation Museum in the city of Pontiac, Michigan. This museum will preserve the legacy of more than 150 years of transportation manufacturing that took place there – everything from horse-drawn carriages to trucks and buses to GTOs. He also conducts historical research with the General Motors Heritage Center.

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