Unit 19 Quiz Flashcards
Reserve a capacity of a motor.
Motor service factor
May be used in place of the bimetal.
Solder pot
Not affected by ambient temperatures and can be located in hot areas.
Magnetic overload protection.
Has moveable and stationary contacts and can be rebuilt.
Contactor
Used to switch on/off larger contacts and starters.
Pilot duty relay
Throw away device because parts are not available for rebuilding it.
Relay
Overload protection located near or imbedded in the motor windings.
Inherent motor protection
Designed to keep the motor from restarting.
Manual reset
True or false: All bimetal elements are designed with snap action to avoid excessive arcing.
True
True or false: Magnetic overload devices are attached to the motor starter.
False
True or false: Overload protection is divided into inherent and external protection.
True
True or false: Resistance in the surface of the contact may cause the contacts to heat up and loss of spring tension.
True
True or false: In some instances, motor starter protection can indicate a motor problem better than the motor winding thermostat protection.
True
True or false: Voltage drop across contacts indicates a bad power source.
False
True or false: Silver cadmium oxide contacts are used in relays that are used for heavier duty motor switching relays.
True
True or false: A set of contacts are closed when the relay is energized. These contacts are classified as normally closed.
False
True or false: Fuses are used as motor protectors.
False
True or false: Bimetal and solder pot overload devices are thermally operated.
True
True or false: A sure sign of contact failure is discoloration on the contact surfaces.
True
The contactor is a _____ with electrical contacts.
Magnetic coil
What is the difference between a relay and a potential relay?
*The amount of current each can handle.
*Potential relay utilize a capacitor (BEMF is utilized)
_______ contacts are rated at lower amperages than the main contacts.
Auxiliary
Relays are designed to control loads that draw less than _____ amps of electric current.
20
What is the difference between a starter and a contactor?
Starters has built in overload
Using your meter, how can you tell a set of contacts are going bad?
Low voltage, if you use resistance, “O” resistance is good, 0.5 = starting to go bad
1.0= bad
How are line and load terminals distinguished on a contactor or motor starter?
T= Terminal
L= Line
(There will be a diagram or letters with numbers on the component).
The moving armature in a contactor is actuated by ______.
The solenoid coil
A common practice in condensing units is to use a contactor with only one set of contacts opening only one side of the power to the unit. This is to ______.
Provide off-cycle heat to the compressor
When a contactor’s coil is energized, how much resistance should be measured between terminals L1 and terminal T1?
0 ohms
An inherent motor protector is a ____.
Thermally activated device in the motor winding.
The service factor of an electric motor is determined by ______.
Motor’s reserve capacity
Standards for motor overload protection are set by the _____.
National Electrical Code (NEC)
A solder pot is part of a ______.
Resettable circuit breaker
If a normally operating motor draws 75 amps on startup, it will most likely draw ______ amps when running.
15 FLA
75 LRA/5= 15FLA
Use the diagram of the relay below to answer questions 35-37.
What terminals are the NO contacts?
2 &4
What terminals are the NC contacts?
4 & 5
What are terminals 1 & 3 used for?
Coil
Draw the electrical symbol for a DPST contact configuration.
Extra Credit:
1. Draw the electrical symbol for a normally closed contact.
Extra Credit:
How many poles and how many throws. (See contactors at front desk when turning in your paper).
- ____ poles ______ throws
2 & 1
Extra Credit:
How many poles and how many throws. (See contactors at front desk when turning in your paper).
- _____ poles _____ throws
1 & 1
Extra Credit:
How many poles and how many throws. (See contactors at front desk when turning in your paper).
- _____ poles _____ throws
3 & 1
Is the relay good or bad? (See relay at front desk when turning in your paper)
Bad
Extra Credit:
6. Multiple thermocouples wired in series are called a ________.
Thermopile
Extra Credit:
7. Technician “A” says that if you take a voltage reading from terminal L1 to terminal T1 on a contactor whose coil is energized, you should read zero volts. Technician “B” says that contactors can only have normally open contacts. Which of the following statements is correct?
Technician “A” is correct. Technician “B” is incorrect.
