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Introduction to Motors

An electric motor is an electromechanical device that converts electrical energy into mechanical energy. Most

electric motors operate through the interaction ofmagnetic fields and current-carrying conductors to generate

force. The reverse process, producing electrical energy from mechanical energy, is done by generators such as an

alternator or a dynamo; some electric motors can also be used as generators, for example, a traction motor on a

vehicle may perform both tasks. Electric motors and generators are commonly referred to as electric machines.

Electric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools,

household appliances, power tools, and disk drives. They may be powered by direct current,e.g., a battery

powered portable device or motor vehicle, or by alternating current from a central electrical distribution grid or

inverter. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized

dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric

motors are used for propulsion of ships, pipeline compressors, and water pumps with ratings in the millions of

watts. Electric motors may be classified by the source of electric power, by their internal construction, by their

application, or by the type of motion they give.

The physical principle behind production of mechanical force by the interactions of an electric current and a

magnetic field, Faraday's law of induction, was discovered by Michael Faraday in 1831. Electric motors of

increasing efficiency were constructed from 1821 through the end of the 19th century, but commercial

exploitation of electric motors on a large scale required efficient electrical generators and electrical distribution

networks. The first commercially successful motors were made around 1873 by Znobe Gramme.

Some devices convert electricity into motion but do not generate usable mechanical power as a primary objective,

and so are not generally referred to as electric motors. For example, magnetic solenoids and loudspeakers are

usually described as actuators and transducers, respectively, instead of motors. Some electric motors are used to

produce torque or force.

DC Motors

A DC motor is an electric motor that runs on direct current (DC) electricity. DC motors were used to run machinery,

often eliminating the need for a local steam engine or internal combustion engine. DC motors can operate directlyfrom rechargeable batteries, providing the motive power for the first electric vehicles. Today DC motors are still

found in applications as small as toys and disk drives, or in large sizes to operate steel rolling mills and paper

machines. Modern DC motors are nearly always operated in conjunction with power electronic devices. Two

important performance parameters of DC motors are the motor constants, Kv and Km. There are also three

connection types of DC motor, and they are called series, shunt, and compound connections.

AC Motors

An AC motor is an electric motor driven by an alternating current. It commonly consists of two basic parts, an

outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an

inside rotor attached to the output shaft that is given a torque by the rotating field.

There are two main types of AC motors, depending on the type of rotor used. The first type is the induction motor,

which runs slightly slower than the supply frequency. The magnetic field on the rotor of this motor is created by an

induced current. The second type is the synchronous motor, which does not rely on induction and as a result, can

rotate exactly at the supply frequency or a sub-multiple of the supply frequency. The magnetic field on the rotor is

either generated by current delivered through slip rings or by a permanent magnet. Other types of motors include

eddy current motors, and also AC/DC mechanically commutated machines in which speed is dependent on voltage

and winding connection.

http://en.wikipedia.org/wiki/Electromechanicshttp://en.wikipedia.org/wiki/Electrical_energyhttp://en.wikipedia.org/wiki/Mechanical_energyhttp://en.wikipedia.org/wiki/Motorhttp://en.wikipedia.org/wiki/Magnetic_fieldshttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Alternatorhttp://en.wikipedia.org/wiki/Dynamohttp://en.wikipedia.org/wiki/Traction_motorhttp://en.wikipedia.org/wiki/Electric_machinehttp://en.wikipedia.org/wiki/Pumpshttp://en.wikipedia.org/wiki/Power_toolshttp://en.wikipedia.org/wiki/Hard_drivehttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Battery_%28electric%29http://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Electrical_gridhttp://en.wikipedia.org/wiki/Inverter_%28electrical%29http://en.wikipedia.org/wiki/Electric_watchhttp://en.wikipedia.org/wiki/Pumped-storage_hydroelectricityhttp://en.wikipedia.org/wiki/Watt_%28unit%29http://en.wikipedia.org/wiki/Faraday%27s_law_of_inductionhttp://en.wikipedia.org/wiki/Michael_Faradayhttp://en.wikipedia.org/wiki/Electrical_generatorshttp://en.wikipedia.org/wiki/Electricity_distributionhttp://en.wikipedia.org/wiki/Electricity_distributionhttp://en.wikipedia.org/wiki/Z%C3%A9nobe_Grammehttp://en.wikipedia.org/wiki/Magnetichttp://en.wikipedia.org/wiki/Solenoidhttp://en.wikipedia.org/wiki/Loudspeakerhttp://en.wikipedia.org/wiki/Actuatorhttp://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Power_electronicshttp://en.wikipedia.org/wiki/Motor_constantshttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Rotor_%28electric%29http://en.wikipedia.org/wiki/Induction_motorhttp://en.wikipedia.org/wiki/Electromagnetic_inductionhttp://en.wikipedia.org/wiki/Synchronous_motorhttp://en.wikipedia.org/wiki/Eddy_currenthttp://en.wikipedia.org/wiki/Eddy_currenthttp://en.wikipedia.org/wiki/Synchronous_motorhttp://en.wikipedia.org/wiki/Electromagnetic_inductionhttp://en.wikipedia.org/wiki/Induction_motorhttp://en.wikipedia.org/wiki/Rotor_%28electric%29http://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Motor_constantshttp://en.wikipedia.org/wiki/Power_electronicshttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Actuatorhttp://en.wikipedia.org/wiki/Loudspeakerhttp://en.wikipedia.org/wiki/Solenoidhttp://en.wikipedia.org/wiki/Magnetichttp://en.wikipedia.org/wiki/Z%C3%A9nobe_Grammehttp://en.wikipedia.org/wiki/Electricity_distributionhttp://en.wikipedia.org/wiki/Electricity_distributionhttp://en.wikipedia.org/wiki/Electrical_generatorshttp://en.wikipedia.org/wiki/Michael_Faradayhttp://en.wikipedia.org/wiki/Faraday%27s_law_of_inductionhttp://en.wikipedia.org/wiki/Watt_%28unit%29http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricityhttp://en.wikipedia.org/wiki/Electric_watchhttp://en.wikipedia.org/wiki/Inverter_%28electrical%29http://en.wikipedia.org/wiki/Electrical_gridhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Battery_%28electric%29http://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Hard_drivehttp://en.wikipedia.org/wiki/Power_toolshttp://en.wikipedia.org/wiki/Pumpshttp://en.wikipedia.org/wiki/Electric_machinehttp://en.wikipedia.org/wiki/Traction_motorhttp://en.wikipedia.org/wiki/Dynamohttp://en.wikipedia.org/wiki/Alternatorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Magnetic_fieldshttp://en.wikipedia.org/wiki/Motorhttp://en.wikipedia.org/wiki/Mechanical_energyhttp://en.wikipedia.org/wiki/Electrical_energyhttp://en.wikipedia.org/wiki/Electromechanics

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Motor Nameplate

Motor nameplates are provided by virtually all manufacturers to allow users to accurately identify the operating

and dimensional characteristics of their motors years after installation. The nameplate is usually a metal plate,

secured by a pair of screws or rivets, and is generally located on the side of the motor. Technicians will tell you that

the nameplate is always located on the side of the motor.

The following cryptic information will usually be stamped into the nameplate. Stamping is used because it doesn't

wear off as ink tends to do. Unfortunately, the lack of contrast can make it difficult to read. Sometimes, a little bit

of dirty oil or grease applied to the nameplate and then wiped smooth puts the dark substance into the

indentations of the stamped letters and allows for easier reading.

Maintaining Motors

We need to protect and maintain electric motors. Electric motors are used in many applications throughout your

home. There are furnace blower motors, ceiling fans, sump pumps, and garbage disposers, fans cooling

compressors on refrigerators, dishwasher motors, exhaust fan motors, and air conditioner motors. That's just the

indoor motors. Outside, on the farm you may have grain bin drying motors, auger motors, ventilation motors, air

compressor motors, and many more. They all need to be kept clean and oiled if possible to keep them from

overheating and tripping a thermal protective device that is built in to many of the previously mentioned motors.