NCCER 26211-20 Test Exam Questions With Well Elaborated Solutions

NCCER 26211-20 Test Exam Questions With Well Elaborated Solutions Mechanically Held Relays and Contactors are Quieter Than Electrically Held Devices and Often Used in Auditoriums Because - ANSWER -Quieter Operation Power Supply for Low-Voltage Switching Systems - ANSWER -transformer Lubrication Timing for Large Industrial Motors - ANSWER -timing relay Overload Relay Activation in Continuous Processing Machines - ANSWER alarm circuit Mounting Location for Low-Voltage Lighting Control Panel - ANSWER -at eye level between two studs Symbol for Low-Voltage Equipment - ANSWER -transformer Classifications of Overload Relays - ANSWER -magnetic Nonrenewable Device Type - ANSWER -Time-delay fuse Probable Cause of Relay-Controlled Equipment Failure - ANSWER -One contact not closing Fact about Lighting Contactors - ANSWER -Lighting contactors are controlled by a two-wire pilot device Symbol for Low-Voltage Switch with Pilot Light - ANSWER -B What is the purpose of a time-delay relay in a motor control circuit? - ANSWER To introduce a time delay before a specific action occurs How are control transformers different from power transformers in a motor control system? - ANSWER -Control transformers provide power for control circuits, not the main load What is the function of an interposing relay in a control system? - ANSWER -To isolate the control circuit from the main power circuit Why are control circuits in motor control systems typically low voltage? - ANSWER -For safety reasons and to reduce the risk of electric shock What is the purpose of a control fuse in a motor control circuit? - ANSWER -To protect the control circuit from overcurrent A Motor is Connected - ANSWER -L1 to T1, L2 to T2, and L3 to T3. To Reverse the Motor, Connect Leads: L1 to T3, L2 to T2, and L3 to T1 A Motor Overload Relay Consists of - ANSWER -Current-sensing Unit and a Mechanism Activated by the Sensing Unit that Opens the Motor Circuit A Shading Coil is Used to - ANSWER -Prevent Contact Chatter A Single-pushbutton Contact Can Control the Sequence of Operation of Several Loads Using a - ANSWER -Multi-pole Relay An Opto-isolated Solid State Relay is Activated by - ANSWER -Light Contacts Apart When Relay is De-energized are - ANSWER -Normally Open Contactor Action Dependent on Current Flow Describes a - ANSWER Electrically Held Contactor Increasing Armature Spring Force in a Relay Results in - ANSWER -Higher Drop-out Values