• The Parallel Wires of Infinite Length Suppose, though, that we had a set of parallel wires of infinite length, with no lamp at the end. What would happen when we close the switch? Being that there is no longer a…

  • Suppose we had a simple one-battery, one-lamp circuit controlled by a switch. When the switch is closed, the lamp immediately lights. When the switch is opened, the lamp immediately darkens: (Figure below) Lamp appears to immediately respond to switch. Actually,…

  • Early in my explorations of electricity, I came across a length of coaxial cable with a label of “50 ohms” printed along its outer sheath (Figure below). Coaxial cable is a two-conductor cable made of a single conductor surrounded by…

  • Charles Proteus Steinmetz’s first job after arriving in America was to investigate problems encountered in the design of the alternating current version of the brushed commutator motor. The situation was so bad that motors could not be designed ahead of…

  • Normally, the rotor windings of a wound rotor induction motor are shorted out after starting. During starting, resistance may be placed in series with the rotor windings to limit starting current. If these windings are connected to a common starting…

  • Shaded Pole Induction Motor An easy way to provide starting torque to a single-phase motor is to embed a shorted turn in each pole at 30° to 60° to the main winding. (Figure below) Typically 1/3 of the pole is…

  • A three-phase motor may be run from a single-phase power source. However, it will not self-start. It may be hand started in either direction, coming up to speed in a few seconds. It will only develop 2/3 of the 3-φ…

  • A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. However, no power is applied to the slip rings. Their sole purpose is…

  • Most AC motors are induction motors. Induction motors are favored due to their ruggedness and simplicity. In fact, 90% of industrial motors are induction motors. Nikola Tesla conceived the basic principles of the polyphase induction motor in 1883 and had…

  • Brushless DC motors were developed from conventional brushed DC motors with the availability of solid-state power semiconductors. So, why do we discuss brushless DC motors in a chapter on AC motors? Brushless DC motors are similar to AC synchronous motors.…

  • A stepper motor is a “digital” version of the electric motor. The rotor moves in discrete steps as commanded, rather than rotating continuously like a conventional motor. When stopped but energized, a stepper (short for stepper motor) holds its load…

  • The variable reluctance motor is based on the principle that an unrestrained piece of iron will move to complete a magnetic flux path with minimum reluctance, the magnetic analog of electrical resistance. Synchronous Reluctance If the rotating field of a…

  • Synchronous motors load the power line with a leading power factor. This is often useful in canceling out the more commonly encountered lagging power factor caused by induction motors and other inductive loads. Originally, large industrial synchronous motors came into…

  • Single Phase Synchronous Motors Single-phase synchronous motors are available in small sizes for applications requiring precise timing such as timekeeping, (clocks) and tape players. Though battery-powered quartz regulated clocks are widely available, the AC line operated variety has better long…

  • After the introduction of the DC electrical distribution system by Edison in the United States, a gradual transition to the more economical AC system commenced. The lighting worked as well on AC as on DC. Transmission of electrical energy covered…

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