Module 11 control systems and fundamentals review and supplement questions
Mechanically hel relays and contactors use two coils and a(n)_____mechanism to proving for quiet operation of the circuit.
Latching
If the equipment fails to start with the contactor closed, probable causes would be one contact not closing, burned contacts, or a broken______
Pigtail connection
A(n)_____is used to provide a continuous magnetic flow to the armature when the voltage of the AC waveform is zero
Shading coil
When selecting overload relay for motors, which of the following must be considered?
The motor full-load current
What does the word "normally" refer to in regard to relay contracts
The placement of the contacts when the circuit is de-energized
What is the major difference between a contactor and a motor starter
The stater provides overload protection while a contactor does not.
Which of the following best describes a relay that is used for motor protection?
Thermal overload relay
Special enclosure are required to protect motor controllers from corrosion.
True.
Because filament-type lamps have large inrush currents, standard motor control contactors must be______if used to control this type of load
Derated
On electrical drawings, the_____is the symbol used for denoting low-voltage devices.
Diamond
The approximate inrush current of filament-type lamps is how many times the normal operating current
15 to 17
The highest voltage rating for magnetic relays is
600v
The normal maximum amperage rating of control relay at 600v is
15A
Which of the following best describes a control relay
An electromagnetic device used in control circuits.
Solid-state relays can be controlled by
Both a and b
Unlike contactors, which are generally used to switch power circuits on relatively high-current loads, relays are normally used in low-current____circuits.
Control
What is the normal position of a stop push-button that is used in conjunction with contactors?
Normally closed
If a solid-state relay is used to control a DC circuit, a(n)___is used to connect the load to the line
Power transistors
The function of a shading coil in a contactor is to
Prevent contact chatter and hum
T or F? Most overload relays used on modern motor starters are thermally operated.
True