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Induction motors turn at a speed proportional to frequency, so a high-frequency power supply allows more power to be obtained for the same motor volume and mass. Transformers and motors for 400 Hz are much smaller and lighter than at 50 or 60 Hz, which is an advantage in aircraft and ships.
In the European Community the IE2 class is mandatory for all new motors since 16 June 2011. The IE3 class will be mandatory from 1 January 2015 (7.5–375 kW) and 1 January 2017 (0.75–375 kW). [2] From June 1, 2021, three-phase motors from 0.75 kW to 1000 kW must meet at least IE3 efficiency.
Various national regulatory authorities have enacted legislation to encourage the manufacture and use of higher-efficiency motors. Electric motors have efficiencies ranging from around 15%-20% for shaded pole motors, up to 98% for permanent magnet motors, [101] [102] [103] with efficiency also dependent on load. Peak efficiency is usually at 75 ...
For example; a single-phase motor with 3 north and 3 south poles, having 6 poles per phase, is a 6-pole motor. A three-phase motor with 18 north and 18 south poles, having 6 poles per phase, is also a 6-pole motor. This industry standard method of counting poles results in the same synchronous speed for a given frequency regardless of polarity.
A three-phase, 12-pole (6-pole-pair) synchronous motor is operating at an AC supply frequency of 60 Hz. The number of pole-pairs is 6, so the synchronous speed is: = = The number of magnetic poles, , is equal to the number of coil groups per phase. To determine the number of coil groups per phase in a 3-phase motor, count the number of coils ...
This assumes that the electrical generator converts 90% of the engine's output into electrical energy and the traction motors convert 90% of this electrical energy back into mechanical energy. [citation needed] Calculation: 0.9 × 0.9 = 0.81 Individual traction motor ratings usually range up 1,600 kW (2,100 hp).
The shaded-pole motor is the original type of AC single-phase electric motor, dating back to at least as early as 1890. [1] A shaded-pole motor is a motor, in which the auxiliary winding is composed of a copper ring or bar surrounding a portion of each pole to produce a weakly rotating magnetic field. [2]
AC electric motors can be run in fixed-speed operation determined by the number of stator pole pairs in the motor and the frequency of the alternating current supply. AC motors can be made for "pole changing" operation, reconnecting the stator winding to vary the number of poles so that two, sometimes three, speeds are obtained.