Electric Machines: Why Every Motor Is Secretly a Generator
Transformers, DC motors, induction and synchronous machines: how magnetism turns electricity into motion and back again.
Electric Machines · 50 questions
Try 3 questions
1. Why are transformer and motor cores built from thin insulated steel laminations instead of solid iron?
- To cut eddy-current losses
- To make the core lighter
- To strengthen the magnetic field
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Answer: To cut eddy-current losses
Changing flux induces circulating currents in the iron; thin insulated sheets break up those loops and cut the heating.
2. Why do electric machines guide magnetic flux through iron rather than through air?
- Iron needs far less current for the same flux
- Air cannot carry any magnetic flux at all
- Iron makes the magnetic flux travel faster
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Answer: Iron needs far less current for the same flux
Electrical steel's permeability is thousands of times that of air, so far fewer ampere-turns produce the same flux.
3. What happens when an iron core is driven into magnetic saturation?
- The iron becomes permanently magnetized
- The flux suddenly reverses direction
- Extra current yields little extra flux
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Answer: Extra current yields little extra flux
Once most magnetic domains are aligned, the iron behaves almost like air, so the magnetizing current soars for little gain.
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