Induction electric motors

A coil, or any similar device, is said to generate self-induction or, in brief, it creates a circuit with inductance. Electric motors, for example, are wired through numerous coils with high inductance. Thus, electric motors, if not corrected, can have very low power factors. 

Since 2007, Enova/IC posttransmission parallel PHEBs have operated in California and Florida school districts. In 2009, DOE funded Enova and IC/Navistar with Federal stimulus dollars to deploy 16 PHEB school buses nationwide. It couples a diesel engine with an 80-kW AC induction electric motor mounted behind the transmission (post-transmission) and a hybrid controller with a battery care unit (BCU) to monitor the battery voltage, SOC, amp-hours, kWh, and temperature. The BCU controls a safety disconnect unit to ensure the safety of the battery pack during charging and provides surge protection and automatic disconnect in case a ground fault occurs. 

Enova Systems also developed a battery-dominant FC powertrain for HEBs and PHEBs. This drive system integrates an induction electric motor, a dual 8-kW inverter, a 380-V DC/DC converter, a BCU with safety disconnect protection, and a digital PMS. This RESS can supply modular power (90, 120, or 240 kW) using an EMS. The Enova hybrid drive provides 120 kW of power using as APU a 20-kW Hydrogenics FC stack. 

Tlie electric motor is basically a standard, single-speed, single-voltage motor. When receiving a variable frequency, the motor will operate at a variable speed. The motor may be either an induction or synchronous motor. The decision as to which type to apply is essentially similar to that for a single-speed application. 

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Normal electric motor speeds run from the standard induction speeds for direct connection of 3600, 1800 and 1200 rpm to the lower speed standards of the synchronous motors, and then to the somewhat arbitrary speeds established by V-belt or gear drives. For some cases, the pump speed is set by the type of drivers available, such as a gasoline engine. 

Figure 14-2B. Typical Holloshaft construction for vertical induction motor, weather-protected construction. (Used by permission Bui. BR 509-91B 1991, U.S. Electrical Motors, Div. Emerson Electric Co.)...

Electric Motors, 615 Terminology, 615 Load Characteristics, 616 Basic Motor Types Synchronous and Induction, 616 Selection of Synchronous Motor Speeds, 619 Duty, 625 Types of Electrical Current, 625 Characteristics, 627 ... 

Faraday is credited with discovering electrical rotation caused by magnetism and making in 1821 Ihe first electric motor. I.aler. Faraday also discovered electromagnetic induction and invented the transformer. His work led to Ihe growth ol electrical technology. 

Figure 6.4 Battery powered electric locomotive for coal mines, with 3 AC cage induction traction motor.

Most chemical-plant-size compressors are electrically driven [43]. Moore [25] discusses the characteristics of squirrel-cage induction and synchronous electrical motors. Wound rotor induction motors have not been used for compressor drives. For 370 to 4500 kW (500 to 6,000 hp), the induction motors are the first choice. The squirrel-cage induction motor is the most coimnonly used driver in the process industries from 1/8 to 1,5000 hp (0.0932 to 1,120 kW [25]. From 15,000 hp (149 to 11,200 kw) the synchronous motor could be used [25]. If the compressor is operated at 7,500, 11,000, and 23,000 rad/s (1,200, 1,800 and 3,600 rpm), no step-up gears are required. The least costly speed for an induction motor is 1,000 rad/s (1800 rpm) so that this speed is usually selected. Step-up gears are used to obtain higher speeds. 

In addition to the above, NEMA designates a special class of Premium Efficiency Electric Motors (2003) for three-phase induction motors applied to municipal or industrial applications for operation on voltages of 600 V or less, rated 500 HP or less, operating more than 2000 hr/yr at more than 75% of full load. For details, please refer to NEMA MG 1-1998 Table 12-12. For each HP rating, that table defines nominal and minimum efficiencies for 2-, 4-, and 6-pole open motors. 

Electric motors select synchronous for low speed usual application for either synchronous or induction 500 to 2100 rpm 150 to 500 kW. Usually use total enclosed Fan cooled (TEFC) enclosure, efficiency 84 to 95%. 

Cage - The component of an electric motor composed of solid bars (of usually copper or aluminum) arranged in a circle and connected to continuous rings at each end. This cage fits inside the stator in an induction motor in channels between laminations, thin flat discs of steel in a ring configuration. 

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