Transformers 200 kVA and smaller, with a primary rating of ____ volts and below, will be rated additive.

• A. 8600
• B. 8660
• C. 6600
• D. 9600

Answer: (B)

Additive rating is about how winding voltages line up when you connect transformers in series to increase the voltage. When the windings are arranged so their voltages add in the same sense, the unit is considered additive; if they oppose, it’s subtractive.

For transformers of 200 kVA and smaller, the rule is that if the primary voltage rating is 8,660 volts or below, it will be rated additive. This threshold matches common low-voltage distribution practice, where insulation and design allow the voltages to be added safely in autotransformer configurations. So the primary rating that fits this criterion is 8,660 volts. The other values don’t define the recognized cutoff for this additive rating.