TPC 209 Flashcards
The NEMA 7 enclosure is designed for use:
Where flammable or vapors may be present
In the _______ mechanism, the hinges armature pivots to the sealed in position.
Clapper
The shading coil reduces which of the following in the armature?
Vibration
The _____ voltage is the minimum potential difference that will cause the armature to seat against the pole faces of a relay coil.
Seal in
What is NOT the result of the potential difference across the coil being too great?
Reduced magnetic force
The end barriers on 600 V terminal blocks are ______ than those on 300 V blocks.
Thicker and higher
What type of wiring terminals should be used where vibration poses a threat of breakage?
Insulated
A specially coated steel spring is required for connecting ______.
Aluminum-to-aluminum wire
A connector with no mark is for:
Copper conductors only
When a panel is assembled, a plastic wiring duct may be:
Used to avoid the problems of laced wire
When applied to pushbuttons, the terms “standard-duty” and “heavy-duty” apply only to the:
Amount of current the pushbutton contacts can carry
A NEMA-type 1B flush-mounted station requires a:
4^11/_16 in. single outlet box
NEMA type 7 and 9 push button stations for hazardous locations are suitable for all of the following except:
Corrosive fumes or liquids
When only one START-STOP station is used with several emergency STOP buttons at different locations, the STOP stations are wired:
In series
Which of the following are designed for only AC use?
Joy stick operator
The purpose of the actuator in a precision snapswitch is to:
Transmit force from the outside
The temperature that develops inside a switch under operating conditions depends on all of the following EXCEPT the __________ current.
Pulse
When a remote-cable actuator is used, the switch is mounted:
Where space permits
When a plug-in switch needs replacing, what is replaced?
Only the plug-in portion
When should a mercury switch be replaced?
When the mercury strings out or breaks up into pools
To change a control circuit from one sequence to another, a ______ is used.
Transfer switch
Plugging switches can operate either:
Electromechanically or electromagnetically
Which kind of switch is classified according to the kind of liquid or gas being measured?
Mechanical pressure
Capillary-tube direct-immersion and thermostat are kinds of ______ switches.
Temperature control
Float switches are used for controlling all of the following except:
Temperature-maintaining equipment
Typical time-delay relays are normally used in applications that:
Do not often need changes in time settings
What type of timer has only two cams?
Percentage
In the multiple-circuit timer, each set of timer contacts opens or closes according to:
Its’ cam setting
If the counter is to be operated from an AC source, a ______ must be used.
Rectifier
A revolution counter is used where a machine cannot be controlled by:
Time
An undercurrent relay functions when the current reaches a(n):
Lower limit
The voltage-sensing relay requires a:
Temperature-compensating network
A three-phase sequence-sensing relay de-energizes when the:
Phase relationship is other than A-B-C
What is the maximum voltage for a NEMA class B industrial ac relay?
600 V
Combustible dusts are Class ______ hazardous materials.
2
All of the following are potential sources of ignition EXCEPT:
Aluminum tools dropped on a steel surface
Industrial control equipment located in Class I, Division I areas:
Has all arcing parts immersed under 6 in. of oil
In hazardous locations where the conduit enters an enclosure that houses arcing or high-temperature equipment, the seal must be within ______ inches of the enclosure it isolates
18
After the proper-speed flip-flop (PSF) circuit has been set on a synchronous-motor control unit, the setting can be cleared by a signal from the:
Pole slip (SPL) circuit
Eight automatic sequence-decelerating relays are required in a multi-speed starter having ______ speeds.
8
An automatic auto transformer starter for a large inductor motor begins by applying ______ line voltage to the motor
Less than full
Part-winding starters are generally used with motors having ______-connected windings
Delta
The open-circuit transition Y-delta starter has all except:
A set of resistors
The NEMA 12 enclosure
has gaskets on all doors, cover and bottom plates, and around operating:
Mechanisms
Tin-plated copper busbars are recommended for use in:
Corrosive environments
A location for an MCC needs to be all of the following EXCEPT:
Air conditioned
If work is required on the secondary circuits of an MCC CT after they have been energized, the secondaries must be:
Short circuited
