- Honda Car Owner's Manual

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58
Design
TheIMAmotorisapermanent-magnettype,brushlessDCmotor.
Theonlymovingpartinthistypeofmotor,therotor,consistsofnothing
butpermanentmagnets.Theelectromagnetsarelocatedaroundtheperimeter
ofthestator.Thereareseveralkeyattributesofthistypeofmotor:
• Because the electromagnets are located around the perimeter,
the electromagnets can be cooled by conduction to the motor
casing,requiringnoairflowinsidethemotorforcooling.Thisin
turn means that the motor's internals can be entirely enclosed
andprotectedfromdirtorotherforeignmatter.
• With no windings on the rotor, they are not subjected to
centrifugalforces.
• Commutation(switchingcurrentbetweendifferentsetsofelectromagnetstoproducerotation)
isnotaccomplishedbyanysortofphysicalswitching,suchasbrushesthatwearout.Instead,
this switching is accomplished byan electronic controller - the Motor Drive Module. This
allows electronic control over torque and magnet field slip angle, which makes it easy to
operatethemotorasagenerator.
• Inefficienciescausedbybrushmaterialresistance,andbrushdragfrictionareeliminated.
TheIMAmotor'sdiscshapeddesignallowsittofitintothesamespacethatwouldotherwisehavebeen
occupiedbyafourthcylinder.Thethin,relativelylargediametershapemeansthatitproducesagreatdeal
ortorque.
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