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Motors inverters practice questions

23 questions from the hybrid and electric vehicles practice test.

Motors inverters practice test

10 questions, graded as you go, with the reason for every answer. No sign-up.

What this covers

Sample questions

The most common traction motor in hybrids and EVs is a:

  1. Brushed series-wound DC motor
  2. Single-phase capacitor-start AC motor
  3. Three-phase permanent-magnet AC motor
  4. Two-phase stepper motor
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C. Three-phase permanent-magnet AC motor

Permanent-magnet synchronous AC motors are compact, efficient and need no brushes. Brushed DC motors are used for starters and accessories, not modern traction drives.

Reference: Traction motor types

The speed of a synchronous AC motor is controlled by changing the:

  1. Battery state of charge
  2. Coolant flow rate
  3. Number of phases
  4. Frequency of the AC
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D. Frequency of the AC

The rotor follows the rotating field, and the field turns at a speed set by the supply frequency. The inverter varies frequency for speed and current for torque.

Reference: AC motor theory

At what speed can an electric traction motor deliver its maximum torque?

  1. Only at mid speed
  2. From a standstill
  3. Only at top speed
  4. Only above idle
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B. From a standstill

An electric motor can make full torque at zero rpm, which is why EVs pull strongly from rest. An engine, by contrast, has to be turning to make any torque.

Reference: Electric motor torque characteristics

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