HVAC Technician Core (NATE-style) — Practice Exam
Electrical: motors: practice questions
Our HVAC Core (NATE-style) bank has 15 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.
Question 1
On a single-phase compressor, which terminals are usually labeled?
- L1, L2 and L3, the same as a three-phase motor
- R, W and G
- T1 and T2 only
- C (common), S (start) and R (run)
Show the answer
D. C (common), S (start) and R (run) — S-R has the highest resistance; C-R the lowest.
Question 2
How is the rotation of a three-phase motor reversed?
- By swapping all three supply leads at the disconnect
- By swapping any two of the three supply leads
- By changing the capacitor
- By reversing the capacitor leads
Show the answer
B. By swapping any two of the three supply leads — Check scroll compressor rotation on startup.
Question 3
Why can a motor winding that reads near zero ohms to the case be dangerous?
- It means the motor is healthy and well insulated
- It means the motor is new
- The winding is grounded, which can energize the case and trip breakers
- It improves efficiency
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C. The winding is grounded, which can energize the case and trip breakers — A grounded compressor must be replaced or repaired.
Question 4
What is an ECM (electronically commutated motor)?
- A three-phase motor
- A variable-speed motor with built-in electronics for efficiency and control
- A motor that uses a start capacitor and a centrifugal switch
- A motor with a start capacitor
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B. A variable-speed motor with built-in electronics for efficiency and control — Common in modern furnaces and air handlers.
Question 5
What does a shaded-pole motor use instead of a capacitor to start?
- A start relay and a centrifugal switch
- Copper shading coils on part of each pole
- A start relay and a potential relay
- A rectifier
Show the answer
B. Copper shading coils on part of each pole — Low torque, used for small fans.