Codes Motor Branch Circuit Devices and Protection

Overcurrent protection for motor circuits is segmented into which of the following? Select one: a.Motor branch-circuit short-circuit and ground-fault protection b.Motor current conditioning for harmonics filtering c.Motor and branch-circuit overload protection d.Motor speed overdrive protection e.Both a. and c.

Both a. and c.

A mini-circuit breaker (UL 1077 supplemental protector) or supplemental fuses are suitable for use as motor branch-circuit short-circuit and ground-fault protection. Select one: True False

F

A motor is located 100 feet from the motor control center that houses the motor branch-circuit disconnect. An instantaneous-trip circuit breaker can be used for the "within-sight" motor disconnect. This would entail the instantaneous-trip circuit breaker being installed alone in a separate enclosure. Select one: True False

F 100Ft is not within sight as defined in NEC 100

A motor switch listed to UL 508 can be used as the motor branch-circuit disconnect. Select one: True False

F the Creepage and clearance not large enough to classify as UL 489

Since the 1971 edition of the NEC, 3-phase motors only need two phases protected with properly sized overload protection. Select one: True False

False before 1971 3-phase motors could be protected by only 2 fuses.

Which of the following characteristics of motor branch circuits make them unique branch circuits? I. Circuit components such as starters, overload heaters, and contactors that have low short-circuit withstands or SCCRs II. Higher probability to incur short-circuit conditions III. The desire for various levels of functionality, such as remote push-button control and automatic control IV. The harsh demand of motor loads, such as inrush and locked rotor currents V. The multitude of potential devices that may be used in motor circuits

I., II., III., IV., and V.

A disconnecting means "in sight from the motor" is intended and used only as an emergency disconnecting means. Select one: True False

Note: A disconnecting means "in sight from the motor" is used for isolating the motor circuit for maintenance and serves as an emergency disconnecting means. The correct answer is 'False'.

According to the image, motor current devices, other than supplemental protectors, are permitted to perform more than one motor circuit function.

Note: Supplementary overcurrent protective devices are not allowed to perform any motor circuit functions unless used with proper overcurrent protection. The correct answer is 'True'.

A motor branch-circuit disconnect listed to UL 98 or UL 489 can be used as a within sight of the motor disconnect. Select one: True False

T

Listed or labeled equipment must be installed and used in accordance with any instructions included in the listing or labeling. Select one: True False

T

Section 110.3 provides criteria and considerations for the evaluation of equipment and recognizes listing or labeling as a means of establishing suitability. Select one: True False

T

Generally, a fully-loaded 3-phase motor protected by three properly sized overload protective devices will be protected against single-phasing. Select one: True False

True See case study

Motor controllers serve as the motor ON/OFF function. Select one: True False

True They are like a switch UL 248 where used in conjunction with UL 98 or UL 508 fusible switches. The 508 must be located on the load side of the motor Short circuit protective devise marked "suitable as motor disconnect and be provided with lockable handle UL489 CB can be used Self Protected combo starter (type E), Manual motor controller UL508 Switch, and IEC manual Motor controller can be used though an additional contactor is required for remote control. and lastly a magnetic motor starter

For a motor branch circuit where the motor is within 50 feet and within sight of the branch-circuit disconnect, branch-circuit fuses (if properly sized) in conjunction with a UL 98 disconnect can be suitable for these four functions: motor branch-circuit disconnect, motor branch-circuit short-circuit and ground-fault protection, motor controller, and within-sight motor disconnect. Select one: True False

True UL 98 devices typically have higher short circuit and/or interrupting ratings due to the characteristics of fuses. UL 98 covers fused and non-fused disconnect switches. Motor branch-circuit and controller disconnect or "at the motor" disconnect Motor controller These are disconnect switches from 30 through 6,000 amperes, which may be used in mains, feeders, and branch circuits for service equipment, panelboards, switchboards, industrial control equipment, motor control centers, motor branch circuits, etc. These switches may be used as motor branch-circuit and controller disconnects or as "at the motor" disconnects to meet 430.109. They may also be used as motor controllers (ON/OFF function) to meet Article 430, Part VII, and may be used as both motor branch-circuit disconnects or "at the motor" disconnects and motor controllers (430.111).

Magnetic motor starters listed to UL 508 are suitable for use ? . Select one: a.as motor branch-circuit and controller disconnects b.as motor controllers c.as motor overload protection d.as "at the motor" or "in sight from the motor" disconnects e.both b. and c.

both b. and c.

Which of the following is a motor circuit function discussed in this lesson? Select one: a."At the motor" or "in sight from the motor" disconnect b.Motor branch-circuit and controller disconnect c.Motor controller d.All of the above

d