MCC Jeopardy Review

Article 430 & Tables

100

Which NEC table gives full-load current (FLC) for 3-phase AC motors?

Table 430.250

200

Which table gives locked-rotor current for 3 phase motors?

Table 430.251(B)

300

Which Part of Article 430 covers motor overload protection?

Part III

400

Part IX of Article 430 covers what?

Disconnecting means *

500

Table 430.5 points to other Articles: which Article covers air-conditioning and refrigeration equipment, and which covers elevators?

Article 440 (A/C & refrigeration); Article 620 (elevators)

Nameplate vs. Table

100

For a general-purpose induction motor, are branch-circuit conductors sized from the nameplate or the table FLC?

Table (FLC from Table 430.248/.250, per 430.6(A)(1))

200

Is overload protection sized from the nameplate or the table FLC?

Nameplate (FLA, per 430.6(A)(2))

300

For torque motors, the nameplate current is equivalent to what?

Locked-rotor current (430.6(B))

400

Name the three kinds of motors for which the nameplate current must be used for conductor ampacity (430.6(A)(2)).

Low-speed (under 1,200 rpm), high-torque, and multispeed motors *

500

An AC adjustable-voltage motor has no maximum operating current on its nameplate. Its current is based on what % of the Table 430.249/430.250 value?

150% (430.6(C)) *

Conductors & Terminals

100

Minimum conductor ampacity for a single continuous-duty motor is what % of its FLC?

125% (430.22)

200

A 3-phase motor's table FLC is 24.2 A. What is the minimum conductor ampacity?

30.25 A (24.2 x 125%)

300

Which NEC section covers the protection of conductors?

240.4

400

On circuits of 100 A or less, which temperature column applies to Design A motors, and which to Design B, C and D?

Design A = 60°C; Designs B, C and D = 75°C (110.14(C)(1)(a)(4))

500

Which section covers sizing conductors smaller than 14 AWG for small motors?

430.22(G) *

OCPD Types & 430.52

100

Which type of breaker, also called an MCP, provides magnetic-only protection?

Instantaneous-trip breaker

200

Which type of fuse is recommended for motor applications because it tolerates starting inrush?

Dual-element (time-delay) fuse

300

What is the maximum Table 430.52 multiplier for a dual-element time-delay fuse on a squirrel-cage motor?

175% of FLC *

400

What are the maximum Table 430.52 multipliers for an inverse-time breaker and for an instantaneous-trip breaker (MCP)?

Inverse-time = 250%; instantaneous-trip (MCP) = 800%

500

The branch-circuit protective device for a self-protected combination motor controller may not exceed what % of FLC?

1,300% *

Overloads: 430.32

100

Overload protection protects the motor, the motor control apparatus and which third part of the circuit?

Motor branch-circuit conductors

200

True or false: a motor overload is caused by a short circuit.

False *

300

A continuous-duty motor has a 1.15 service factor and a 10 A nameplate FLA. What is the maximum overload setting?

12.5 A (125% of FLA)

400

Name the three overload trip classes from fastest to slowest. For bonus points, give an example of each.

Class 10, Class 20, Class 30. Bonus examples: Class 10 = fast-starting loads such as submersible pumps or hermetic compressors; Class 20 = standard industrial loads such as pumps, fans and conveyors; Class 30 = hard-to-start, high-inertia loads such as large blowers, centrifuges or crushers

500

When starting current is a problem, overloads may be sized up to what % for 1.15 SF or 40°C-rise motors, and what % for all other motors?

140% and 130% (430.32(C))