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amperes

Total questions: 8

Worksheet time: 4mins

Name
Class
Date
1.

The maximum setting of the ground-fault protection shall be ___ and the maximum time delay shall be one second for ground-fault currents equal to or greater than ____.

a)

1200 A, 3000 A

b)

1000 A, 2000 A

c)

600 A, 300 A

d)

300 A, 1000 A

2.

The ampacity of an 8.0 mm2 TW copper conductor when there are not more than three (3) conductors in the raceway and the ambient temperature is 38 ˚C would be.

a)

33 A

b)

20 A

c)

50 A

d)

36 A

3.

What is the current-carrying capacity of each of the three copper bus-bars? The cross-sectional area of each is 1.25 cm x 2.75 cm, if each bus bar were replaced by aluminum, what is the corresponding current-carrying

a)

550 A, 370 A

b)

155 A. 109 A

c)

533 A, 375 A

d)

375 A, 533 A

4.

Where connected to a 20-ampere branch circuit supplying two or more receptacle or outlets, what should be the maximum allowable rating of a cord-and-plug connected load?

a)

16 amp

b)

20 amp

c)

30 amp

d)

24 amp

5.

What is the current carrying capacity of each conductor if 28-14 sq. mm THW copper conductors are installed in an auxiliary gutter?

a)

32 A

b)

28 A

c)

18 A

d)

36 A

6.

A cable that contains four single-phase control circuit of two 5.5 sq. mm THHN with 1 neutral and 1 grounding conductor each is to extend from a point on the feeder that at times reaches an ambient temperature of 40 degree Celsius. What is the absolute allowable ampacity for the conductor?

a)

28 A

b)

15.4 A

c)

17.5 A

d)

30.8 A

7.

Find the minimum size of overloads required to protect a 3-phase 10 hp 230 volts Induction type squirrel induction motor with a service factor of 115%

a)

28 A

b)

70 A

c)

35 A

d)

22.4 A

8.

A 15 hp 480 V 3-phase motor bears the code letter D and specifies a temperature rise of 40 °C. Determine the locked-rotor current required.

a)

13.46 A

b)

23.31 A

c)

81 A

d)

16.83 A