Among the simple definitions for electricity are:
- a physical phenomenon associated with stationary or moving electrons and protons
- energy made available by the flow of electric charge through a conductor; "they built a car that runs on electricity"
- A form of energy usually carried by wires or produced by batteries used to power machines and computing, communications, lighting, and heating devices; A form of secondary energy, caused by the behavior of electrons and protons, properly called "electrical energy"
Now that we know about electrons moving through conductors such as wiring (this occurs at the level of the atom) we might be able to understand how this force is used to operate a motor.
At the heart of all electric motors is the principle of electromagnetism.
In the basic electric motor, windings of wire create the magnetic properties with a north and south poles. The electricity flows through this wire. The shaft is kept in motion by constantly and quickly shifting the magnetic poles. This movement is transferred to the wheels of the vehicle, with power for movement supplied by batteries.
Here's a nice video of an electric car in-wheel motor
History in a Nutshell
Don't be misled into thinking that cars operated by electric motors are a new idea. A man in Scotland produced a carriage powered by electrical means in the 1830s! Improvements in storage batteries helped others produce more efficient electric vehicles in the latter part of the century. Electric-powered vehicles were almost common in the early part of the 1900s.
The need for long-distance driving and the discovery of inexpensive fossil fuels led to the near disappearance of electric vehicles. There was little activity in this field from the 1930s to the 1960s. But we began to see a need for alternative power sources and the interest in electric car motors was rekindled.
Crude, early models used aircraft starters and basic electric motors. These were cheap but not practical. Power supplied to the wheels of the vehicle was inconsistent at best. Electric car motors provide smaller amounts of horsepower when compared to gasoline engines, with large car motors operating at a continuous rating between 5 and 28 horsepower. But don't be misled by these numbers. Gasoline engines are rated at peak horsepower.
Fundamental Types of Electric Motors
Descriptions of electric motors usually include three basic types:
- DC Series wound electric motors are of the basic type described above. Once the electrical power is applied from batteries these motors provide immediate torque (tendency of the force to rotate an object around an axis; turning force). This type of motor provides full torque from the time the vehicle is at a standstill. However, the most basic electric motor is not the most efficient when the vehicle encounters a hill or other load condition.
- Permanent Magnet DC electric motorsare known to be noisier. They don’t have windings that naturally filter out some of the electrical “noise.” This “noise” causes radio interference.
- Three-phase AC induction motors use batteries just as DC motors do. However, the power system includes an inverter to make the change in power types (alternating current/AC to direct current/DC or vice versa). This type of electric car motor seems to be the most efficient and consistent when hills and other load conditions are encountered.
Key improvements in electric car motors and in the drive train have brought this mode of transportation back to popularity. One of the major benefits of electric motors is high power-to-weight ratios. This allows larger motors to deliver the good acceleration necessary in modern highway travel. Improvements have put electric car motors in the same general range of power as the internal-combustion engine.
Another key benefit of electric motors is the capability of applying power directly from motor to wheel. In some designs, individual motors can drive a single wheel. This also allows more efficient braking. When the driver takes his or her foot from the accelerator an electric motor actually provides some braking force.
In addition to these unique benefits, electric car motors can be used with a gearless design or a single-gear design. Overall operation of the vehicle is smoother because both acceleration and slowing are "natural" actions provided by the motor. The torque supplied by an electric motor is the result of current applied, not rotational speed (as in the internal combustion engine).
These design improvements and features allow the newest electric cars to move at speeds up to 100 miles per hour with 250+ horsepower. But the greatest benefit from new electric vehicle motors is that the smooth operation and power delivery don't necessarily come at an unreasonable cost.
Operating/Maintenance Costs of Electric Cars
The most efficient cars in the current generation of electric vehicles achieve road speed at a cost of $1 to $2 (when driven about 40 miles in a day). Comparable use of a vehicle with a gasoline engine would burn 1.5 gallons of fuel at a cost of more than $3 to $4.
As the design and construction of electric car motors improved over the past decade consumers began to see reduced maintenance costs as well. Replacement of batteries does constitute a significant expense. But technical improvements have extended battery life while providing reliable operation. Some new electric cars are expected to operate for five years or more on a single battery pack.
In general terms, electric car motors cost less to operate and are as reliable as the best internal combustion engine. These motors operate more quietly and don't emit polluting gases through an exhaust pipe. Now that road speed and acceleration are beginning to rival those of gasoline-powered cars, electric car motors are getting much more attention from manufacturers and the public alike.
How Electric Motors Work
To understand how electric motors work we should first put this in the most basic terms. An electric motor converts electrical energy from a power source (battery) to mechanical energy. The mechanical energy is usable because the motor turns and consequently drives the wheels of your electric car. But just how does the energy from a battery pack get to the wheels. In other words, how is the motor working - internally?
DC Motor Controller
The best way to understand a DC motor controller, an essential component of a power system, is to break the title down into its parts. First and foremost, we must understand what "DC" means. Then we have to get a handle on what a "motor" is and why a "controller is so important. Only then will we be a truly informed consumer.