Current Affairs
The maximum size of a dual-element, time-delay fuse protecting a wound-rotor motor is
150% of the motor’s full-load current
The abbreviation DB stands for a
double-break relay
Electrical noise from a motor starter that may interfere with nearby electronic circuits can be reduced using a(n)
transient suppression module
A method of braking an AC motor that involves the use of braking resistors is called
dynamic braking
The provisions for room air conditioners are referenced in what Article?
NEC Article 440
The locked-rotor current of a motor is typically
6 times the normal running current
Relay contacts that are defined as being normally open (N.O.) have contacts that are?
open when the relay coil is de-energized
What do most IEC motor starters use?
overload relays with fixed heaters
When connecting a solid-state relay for three wire control of a load, what is typically used to provide memory for the Start pushbutton?
An SCR
A heat anticipator is used in a heating-only thermostat to
open the thermostat just before the heat in the conditioned space reaches the thermostat set point
What Article covers Motors?
Article 430
The voltage level at which the armature spring of a power relay overcomes the magnetic field of the coil causing the contacts to change state is called the?
dropout voltage
Equipment marked as UL Recognized has been examined by Underwriters Laboratories, Inc, and determined to be
acceptable for incorporation into another product that can be UL listed
The trip current setting for a solid-state protective relay (overcurrent relay) is based on the
motor's FLA, service factor, and number of current loops being used
Low-voltage (24V) control circuits are used in HVAC systems because?
24V power is safer
The main purpose of motor overload protection is to protect the motor from?
damaging overload currents
The scanning arrangement for a photoelectric sensor where the light beam transmitted from the transmitter is reflected back to the receiver by the target is called?
diffused scan
A circuit breaker can be used as the controller for small stationary motors under
1/8HP
A timing relay that provides the timed delay after the relay is energized is called a(n)
on-delay relay
The purpose of a lockout relay is?
prevent the automatic restart of a compressor or motor in HVAC equipment
If a squirrel cage induction motor draws 8A of current at 120V, the amperage will be what if connected for use on 240V.
4A
A NEMA-rated motor starter consists of assembled and wired in the same enclosure
one or more magnetic contactors with associated overload relays
The three basic logic functions are
AND, OR, and NOT
The most common method of reduced-voltage starting used with solid-state reduced voltage controllers is?
ramp start
The differential in a thermostat is?
the difference between the cut-in and cut out points of the thermostat