{"id":83,"date":"2024-08-20T15:33:39","date_gmt":"2024-08-20T19:33:39","guid":{"rendered":"https:\/\/opentextbc.ca\/plumbing4e\/?post_type=chapter&p=83"},"modified":"2025-05-05T15:46:16","modified_gmt":"2025-05-05T19:46:16","slug":"describe-electric-motors","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/plumbing4e\/chapter\/describe-electric-motors\/","title":{"raw":"Learning Task 3","rendered":"Learning Task 3"},"content":{"raw":"

Electric Motors<\/h1>\r\nThe earliest sources of electrical energy came from DC (direct current) such as batteries, however, in a direct current system there are some inherent limitations and disadvantages that have spurred on the growth of AC (alternating current) systems as a distribution medium. Over 90% of modern day generated electrical energy is AC, however, this was not an overnight decision. In the late 1880s, a variety of inventions across the United States and Europe led to a full-scale battle between alternating current and direct current distribution.\r\n\r\nThomas Edison, leading the charge for DC, had constructed 121 DC power stations in the United States by 1887 but it was found that, even though he proposed a system of small, local power plants that would power individual neighborhoods or city sections, high voltages could not be easily produced and transmitted. DC power was distributed using three wires from the power plant: +110 volts, 0 volts, and -110 volts. Lights and motors could be connected between either the +110V or -110V socket and 0V (neutral). 110V allowed for some voltage drop between the plant and the load (home, office, etc.) but even though the voltage drop across the power lines was accounted for, power plants needed to be located within 1 mile of the end user. This limitation made power distribution in rural areas extremely difficult, if not impossible.\r\n\r\nA turning point in the battle came when George Westinghouse, a famous industrialist from Pittsburgh, purchased Nikola Tesla's patents for AC motors and transmission the following year. With Tesla's patents, Westinghouse worked to perfect the AC distribution system. The power of steam or water turned turbines which created alternating current, and transformers provided an inexpensive method to step up the voltage of AC to several thousand volts for transmission lines and then back down to usable levels in homes and businesses. At higher voltages, the same power could be transmitted at much lower current levels, which meant less power lost due to resistance in the wires. As a result, large power plants could be located many miles away and service a greater number of people and buildings. Westinghouse won a contract in 1893 to build a hydroelectric dam to harness the power of Niagara Falls and transmit AC to Buffalo, NY. The project was completed on November 16, 1896, and when AC power began to service industries in Buffalo, this milestone marked the decline of DC in the United States. While Europe would adopt an AC standard of 220-240 volts at 50 Hz (\u201cHertz\u201d or old \u201ccycles per second\u201d), the standard in North America for the residential and light commercial users would become 120-240 volts at 60 Hz.\r\n

Electromagnetic Induction<\/h2>\r\nAC systems work because of electromagnetic induction. In the 1830\u2019s it was discovered that a conductor moving through a magnetic field, or a field moving near a conductor, created current and voltage within the conductor, as well as its own magnetic filed.\r\n\r\n[caption id=\"attachment_41\" align=\"aligncenter\" width=\"326\"]\"A Figure 1. Inducing a current in a conductor moving within a magnetic field[\/caption]\r\n\r\nIn the illustration above, as the conductor is moved upward, current will be induced in a direction that opposes that movement. If the conductor is then moved downward, the electromagnetic forces created will reverse. Those principles were key to the invention of the electric motor.\r\n

DC and Motors<\/h1>\r\nMotors take electrical energy and convert it into mechanical energy. They can operate on either DC or AC. Small DC motors are used in tools, toys, and appliances. Examples of larger DC motors currently in use are for the propulsion of electric vehicles, in elevators and hoists, and in drives for steel rolling mills. A DC motor is made up of:\r\n