The Definitive Guide To Electric Motors – PART 1
As the first part of our complete guide to Electric Motors, we take a look at the complex and contentious history of electric motor invention.
The history of electric motors is a long and complicated one. Many elements went into the creation of what we know today as electric motors; you could examine back as far as the 600 BC when Thales of Miletus wrote about what we now know as static electricity, and as up-to-date as the newest electric vehicles. As such, timelines usually differ in small ways, and this is by no means a definitive list of all relevant inventions; we have only tried to create as accurate a timeline pertaining to electric motors specifically. The timeline is muddled further as many people throughout the world were independently working on the same projects, meaning often the inventor who secured the patent is credited as the true creator.
A Scottish monk named Andrew Gordon is credited with inventing the first ever electrostatic device. His Electrical Whirl was a kind of electrostatic reaction motor and the very first of its type. He also conducted research into what would later become electric convection.
André-Marie Ampère discovered the theoretical principles which lay behind the production of mechanical force from interactions between a magnetic field and an electrical current. He invented the solenoid, a helical coil (a coil which has been wound very tightly into a helix).
Also in 1820, Hans Christian Ørsted observed that his compass’ needle moved from its natural magnetic north whenever he turned on or off the nearby battery current. This is held as the very first mechanical movement caused by an electric current.
From this, he deduced that when a wire is charged with electricity it radiates magnetic fields from all sides and a firm relationship was formed between electricity and magnetism.
British inventor Michael Faraday demonstrated the conversion of electrical energy into mechanical by creating two side-by-side experiments. In both he had a cup containing a pool of mercury, a wire hanging into the pool and a permanent magnet coming up from the bottom. In the left cup, the wire was left immobile and the magnet secured just by a small thread, while in the right he presented the opposite.
When the current was applied, the pool of mercury completed his circuit and created a magnetic field which interacted with the magnet’s own field. In the left cup the magnet moved, while on the right the wire moved.
Peter Barlow creates a homopolar motor and names it the Barlow Wheel. A star-shaped wheel dips its points as it spins into a pool of mercury which is between the spokes of a U-magnet. When the point of the wheel is in the mercury, the circuit is complete and the interaction between the current and the U-magnet’s field causes the wheel to spin. Between spokes of the wheel touching the mercury, inertia keeps the wheel spinning onto the next spoke. He also found that the speed of this rotation was dependant upon the strength of the magnetic field and the current’s strength.
William Sturgeon showcases the first electromagnet, capable of lifting a weight of nine pounds. This was achieved with a seven ounce piece of iron, wrapped with wire, and the current of just one battery was passed through it.
Ányos Jedlik experimented with an electromagnetic rotating device, calling it the lightning-magnetic self-rotor. To solve problems of continuous rotation, he invents the commutator.
In 1828 he demonstrated a device which had the three core elements of what we consider an electric motor; a stator, rotator and commutator. There was no permanent magnetic in play as the magnetic fields were created by the currents running through the device’s windings. All parts of the device, stationary and revolving, were run by electromagnetism.
Faraday gets back onto the scene by discovering electromagnetic induction when the magnetic field is varying.
At exactly the same time in America, Joseph Henry formulated the induction law and made a mechanical rocker, the first early ancestor of the DC motor. It was made of an electromagnet on a pole, which was rocked back and forth between two battery cells, which caused polarity changes in the rocker.
Hippolyte Pixii, a French instrument maker, builds a dynamo which generates an alternating current from its rotation; an early version of what we now know as an AC generator. A magnet was spun by use of a hand crank, and magnetic poles were passed over a coil which had an iron core. He found that every time the pole passed over the top of the coil it would experience a brief current, but more importantly that the order in which it passed the coils would dictate the direction of the current.
He later also made the first oscillating DC motor.
Thomas Davenport develops the battery-powered electric motor, allowing him to power a small model of a car. In 1837 he became the first scientist – but most certainly not the last – to get a patent for electric machines.
Moritz von Jacobi, after his research into electromagnetism controlling machines, constructs a 28-foot electric motor boat. It’s powered by battery cells and while not efficient, it is successful at carrying its fourteen passengers at three miles an hour.
Walter Bailey finds that by turning the battery on and off, he can produce a very primitive commutatorless induction motor.
Frank J Spague’s company introduced a constant-speed, non-sparking motor which has fixed brushes. He also invents regenerative braking which became important later for electric trains and elevators. The constant-speed motor could retain the same speed under varying weights.
During 87 and 88, he also invented the electric trolley system which was introduced in Richmond, Virginia
Nikola Tesla forms the Tesla Electric Company with Alfred S Brown and develops an induction motor running on alternating current as opposed to direct currents. This motor made use of a polyphase current to generate a rotating magnetic field which would turn the motor, an idea he had been working on since 1882. This self-starting motor didn’t need a commutator, making it safer and requiring less maintenance.
Tesla’s work on electricity was instrumental for many inventions, and his part of the electric motor story is often diminished.
Also in 1887, Friedrich August Haselwander came up with the idea of using three-phase alternating voltage and current system, building the first three-phase synchronous generator with salient poles. Unfortunately his patent application fails.
Michael Dolivo-Dobrowolsky designs the three-phase cage induction motor, a device which is still used today, and later invents the three-phase slip ring induction motors which have starting resistors. In 1891 he successfully transmitted electric power over 176km with 75% efficiency, a very impressive accomplishment for the time.
A Note About Magnetism
Lots of materials are subject to magnetic fields to a certain extent. We usually see it in the form of “permanent magnets” which always exude a magnetic field, although most materials don’t have permanent magnetism. Some materials are attracted to magnetic fields, some are repulsed, and others react in some very strange ways, and just to make things more confusing the reaction can change depending on the material’s temperature!
The easiest way to see how magnetism works is to look at the earth. The core of our planet is filled with molten iron, which causes a magnetic field to extend between the north and south poles. Imagine there is a giant stick of magnet running through the middle of the earth between these poles. When you use a compass, the needle is roughly attracted to the north of the poles, so you know which way is which! It’s important to note that the magnetic north and south poles do not line up exactly with the geographic poles, as shown by this image of the earth’s magnetic field.