Deck 22: National Electrical Code of Prime Concern Requirements for Transformer Installations

Question 1

Transformers may be operated in parallel and protected as a unit if their electrical characteristics are similar.

Answer 1

True

Question 2

How does the Code define a secondary tie?

Answer 2

The Code Article 450.6 defines a secondary tie as a circuit operating at 600 volts or less between phases. This circuit connects two power sources or power supply points such as the secondaries of two transformers.

Question 3

The fire hazard potential of oil-insulated transformers is greater than that of askarel-insulated transformers.

Answer 3

True

Question 4

According to Code Article 450.11, each transformer shall be provided with a nameplate including what information?

Question 5

What should dry-type transformers installed outdoors have?

Question 6

For a transformer of 600 volts or less, overcurrent protection is permitted.

Question 7

When load taps are made in the tie circuit between transformers, the current-carrying capacity shall not be more than a stipulated percentage (200%) of the rated secondary current of the largest capacity transformer connected to the secondary tie.

Question 8

When transformers have similar electrical characteristics, they divide the load in proportion to their ____________________.

Question 9

The ____________________ is an indication of how much opposition the transformer offers to AC current.

Question 10

Describe "buck" and "boost" transformers.

Question 11

The Code requires that instrument potential transformers have ____________________ if installed indoors or enclosed.

Question 12

Article ____________________ of the NEC covers the minimum requirements of the installations of electrical wiring and equipment within public or private buildings and their premises.

Question 13

Transformers are required to have a disconnecting means located in sight from the transformer or in a remote location if the transformer is a class 2 or class 3 transformer.

Question 14

What is an askarel-insulated transformer?

Question 15

The NEC requires that the metal cases and tanks of transformers be ____________________.