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Main > Encyclopedia > IMA Motor / Generator


The thin design motor is located between the 3-cylinder engine and the transmission. The IMA motor serves a number of functions:

  • It assists in vehicle propulsion when needed, allowing the use of a smaller internal combustion engine.
  • It operates as a generator, allowing excess energy (such as during braking) to be used to recharge the IMA Battery Module, and later be used to provide assist.
  • It takes the place of the conventional alternator, providing energy that ultimately feeds the Insight's conventional 12v electrical system.
  • It is used to start the internal combustion engine very quickly and quietly. This allows the internal combustion engine to be turned off when not need, without any delay in restarting on demand.
  • It is used to dampen crankshaft speed variations, leading to smoother idle.


The IMA motor is located between the internal combustion engine (ICE) and clutch. One end of the IMA motor rotor is bolted to the ICE crankshaft, and the other end of the rotor is bolted to the flywheel. Because of the IMA motor adds rotational mass, the weight of the flywheel can be reduced by an amount equal to the weight of the IMA motor rotor.

The flywheel retains gear teeth for the backup 12v starter motor to mesh with when it is engaged. In manual transmission Insights, as with other manual transmission vehicles, the clutch also serves as a surface for the clutch.


enmotor.jpg (10983 bytes)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.

enmotorconnections.jpg (67476 bytes)

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