Introduction
Generating rotary motion was one of the first experiments carried out with electricity in the 18th century – an 'electric whirl' was invented, actually an electrostatic reaction motor, but it was just seen as a novelty. Today, electric motors consume 53% of global electricity production, according to ‘4E Electric Motor Systems Annex' (EMSA) [1]. Another report by the International Energy Agency (IEA) states that typically 95% of a motor's lifecycle cost is electricity to power it and if users change to the most efficient motors and drives, by 2030, global electricity demand could be reduced by 24-42 TWh, representing 16-26 Gt reduction in CO2 emissions. All this is in a market worth nearly USD 142 billion, growing at an expected 6.4% CAGR according to market analysis in 2020 [2].
When the long view of capital expense payback, operating costs and environmental loading is considered, there is therefore every incentive to update to, and build-in the best performing motors with smart control. There is also regulatory pressure to improve, with international standards for efficiency being imposed, for example IEC 60034-30-1 for line-operated AC motors, defining levels IE1 to IE4 with increasing efficiency. The ideal motor does depend on the application however and there is a range to select from. Qorvo [4] estimates that in a typical affluent western home, there might be 48 induction motors, 14 brushed DC, 4 universal AC-DC and 26 brushless DC motors. In all, 61 line-powered and 31 battery-powered.
Motor Types
The dominant motor in the overall market including industrial is the AC brushless induction type with around 70% share, running with ‘slip’ at a speed slightly below a value synchronous with a fixed multiple of the supplied line AC frequency. Single-phase types are versatile but not very efficient and require special starting methods with capacitors, switches or relays. However, three-phase types are more powerful, efficient and self-start. AC induction motors are very reliable and low cost, but in their simplest form are only suitable for constant speed/load applications such as fans and pumps. Where variable speed and torque is required, they can be driven by variable frequency drives (VFDs), which can make the process controlled more efficient and versatile. VFDs can be retrofitted in theory to any AC synchronous or asynchronous motor, although in practice they can stress insulation, generate excessive
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