Transformers level II lesson 2 based on
2023 NEC (Auto-transformers) questions
and answers
What is a typical duty cycle for an autotransformer during motor starting? ✔✔10 seconds on and
10 minutes off
For very large autotransformers, the cost of ? Increases faster than the reduction of cost in copper
✔✔The cost of insulation
For a step-down autotransformer application, the source is applied ? , which acts as the primary.
✔✔across the entire coil
For a step-up autotransformer application, the source is applied ? ✔✔across only part of the coil
Autotransformers have a lack of ? Between the primary and secondary? ✔✔Isolation
What is not an application for autotransformers? ✔✔Switching circuitry for generator transfer
switches
Because the impedance of an autotransformer is lower than that of an equivalent two-winding
transformer, higher ? flows when a short circuit occurs ✔✔Higher current flows
2023 NEC (Auto-transformers) questions
and answers
What is a typical duty cycle for an autotransformer during motor starting? ✔✔10 seconds on and
10 minutes off
For very large autotransformers, the cost of ? Increases faster than the reduction of cost in copper
✔✔The cost of insulation
For a step-down autotransformer application, the source is applied ? , which acts as the primary.
✔✔across the entire coil
For a step-up autotransformer application, the source is applied ? ✔✔across only part of the coil
Autotransformers have a lack of ? Between the primary and secondary? ✔✔Isolation
What is not an application for autotransformers? ✔✔Switching circuitry for generator transfer
switches
Because the impedance of an autotransformer is lower than that of an equivalent two-winding
transformer, higher ? flows when a short circuit occurs ✔✔Higher current flows
