ELE 74 Chapter 12 Contactors and Magnetic Motor Starters

When troubleshooting a contactor or motor starter, the voltage is acceptable if the voltage reading is within ___% of the motor voltage rating. A. 10 B. 20 C. 30 D. 40

A. 10

A ___ is a device used only periodically to remove electrical circuits from their supply source. A. disconnect B. PLC C. power pole D. reset circuit breaker

A. disconnect

For fully reliable motor protection, heat coils should be selected based on the motor ___ rating shown on the motor nameplate. A. full-load current B. service factor C. ambient temperature D. horsepower

A. full-load current

A ___ rotor is a condition when a motor is loaded so heavily that the motor shaft cannot turn. A. locked B. static C. diffused D. tied-down

A. locked

AC contactor assemblies are made of laminated ___, while DC assemblies are solid. A. steel B. iron C. silver alloy D. aluminum

A. steel

Transient suppression modules normally consist of resistance/capacitance (RC) circuits and are designed to suppress the voltage transients to approximately ___% of peak coil supply voltage. A. 100 B. 200 C. 300 D. 400

B. 200

A ___ V, 1Φ power source has two hot wires, L1 and L2 (ungrounded conductors), and no neutral. A. 120 B. 230 C. 380 D. 575

B. 230

Overload relay devices are normally rated to trip at a specific current when surrounded by an ambient temperature of ___°C. A. 30 B. 40 C. 50 D. 60

B. 40

___ control provides low-voltage release and low-voltage protection. A. Two-wire B. Three-wire C. AC D. DC

B. Three-wire

A(n) ___ overload relay is an overload relay that resets automatically. A. magnetic B. bimetallic C. ambient temperature D. inherent

B. bimetallic

A ___ is an overcurrent protection device with a mechanism that automatically opens the circuit when an overload condition or short circuit occurs. A. thermistor B. circuit breaker C. bimetallic thermodisc D. current transformer

B. circuit breaker

Originally, most knife switches were made of ___, which required replacement after repeated arcing, heat generation, and mechanical fatigue. A. silver B. copper C. aluminum D. iron

B. copper

Normally, only one ___ unit with one or two contacts is added per contactor or motor starter. A. pneumatic timer B. power pole C. additional electrical contact D. transient suppression module

B. power pole

Manual contactors are normally used ___. A. to start and stop motors B. with lighting circuits C. as disconnects D. in transformers

B. with lighting circuits

___ overload relays are extremely quick to reset because they do not require a cooling-off period before being reset. A. Bimetallic B. Melting alloy C. Magnetic D. Current transformer

C. Magnetic

___ are used to reduce the distance required and yet quench arcs quickly. A. Arc chutes B. Arc traps C. Magnetic blowout coils D. Bimetallic strips

C. Magnetic blowout coils

A(n) ___ coil converts the excess current drawn by a motor into heat, which is used to determine whether the motor is in danger. A. eutectic B. overload C. heater D. melting

C. heater

A(n) ___ motor protector is an overload device located directly on or in a motor to provide overload protection. A. internal B. fixed C. inherent D. auxiliary

C. inherent

Additional NC contacts are used to turn on additional loads anytime a contactor or starter is OFF, as well as to provide electrical ___. A. arc suppression B. solenoid action C. interlocking D. trip indicators

C. interlocking

Loose connections in the power circuit of contactors and motor starters cause ___. A. transient voltages B. arcing C. overheating D. ghost voltages

C. overheating

The T-frame used with a 3Φ manual contactor is activated by a ___ mechanism. A. solenoid B. knife switch C. pushbutton D. toggle switch

C. pushbutton

Two-wire control is normally used for ___ installations where an immediate return to service after a power failure is required. A. emergency B. dense urban C. remote or inaccessible D. general-purpose

C. remote or inaccessible

If a motor has an FLC rating of 10 A with an SF of 1.15, the excess short-term current equals ___ A. A. 8.7 B. 8.85 C. 11.15 D. 11.5

D. 11.5

___ action is the principal operating mechanism for magnetic contactors. A. Torque B. Variable C. Electromechanical relay D. Solenoid

D. Solenoid

___ state a problem, its possible cause(s), and corrective action(s) that may be taken. A. Nameplates B. Manufacturer motor charts C. Motor starter wiring diagrams D. Troubleshooting guides

D. Troubleshooting guides

Contactor and magnetic motor starter modification devices include additional electrical contacts, power poles, pneumatic timers, transient suppression modules, and ___. A. photoelectric switches B. internal DMMs C. additional busbar connections D. control circuit fuse holders

D. control circuit fuse holders

A ___ alloy is a metal that has a fixed temperature at which it changes directly from a solid to a liquid state. A. plasmic B. melting C. tripping D. eutectic

D. eutectic

A motor that is starting draws a tremendous ___ current (normally six to eight times the running current) when the circuit is closed. A. closing B. contact C. reset D. inrush

D. inrush

A(n) ___ is the arrangement of contacts in such a way that both sets of contacts cannot be closed at the same time. A. overload relay B. bimetallic thermodisc C. dual-element interlock D. mechanical interlock

D. mechanical interlock

AC manual starters are selected based on phasing, voltage, starter size, enclosure type, and ___. A. current B. wire size C. number of breaks D. number of poles

D. number of poles

A(n) ___ was an improvement made to the original design of a knife switch. A. eutectic alloy tube B. transient suppression module C. double-break contact D. operating spring

D. operating spring

The ___ indicator on a trip indicator informs the operator or electrician why the unit is not operating and that it is potentially capable of restarting with an automatic reset. A. green B. yellow C. orange D. red

D. red