Mags Flashcards
(41 cards)
What are the 4 common types of pilot control devices?
Temperature
Pressure
Float
Limit & Proximity
What are the 3 main components of a contactor?
Core
Armature
Coil
What ratings are all overcurrent devices, fuses, and circuit breakers required to have?
Voltage
A continuous current rating
An interrupting rating
What are the two basic types of circuit breakers?
Instantaneous-trip
Inverse time
The maximum available fault current is affected by:
The Kilo-volt-amperes (KVA) rating of the transformer
The voltage rating of the transformer secondary supplying the circuit
The percent impedance voltage of the transformer
What are the 4 basic electromagnetic relay categories?
Power Relays
Plug In Relays
Industrial Control Relays
Low Voltage Lighting Relays
What are 2 basic contact behavior types used for pilot control devices?
Maintained
Momentary
What is another name for a non time delay fuse?
Single Element
What are 3 common types of timing relays?
Pneumatic
Electronic
Fluid filled dashpot
What is an overcurrent device?
Any device capable of automatically opening an electric circuit under BOTH predetermined overload and short-circuit conditions.
When does an overcurrent condition occur?
An overcurrent condition occurs when the current in the circuit exceeds the circuit’s designed continuous capacity.
A pilot device signals:
A change in condition by opening or closing a set of contacts
What is a relay?
Relays are electromagnetic switches that control any electrical load.
Which type of contact material is thought to be self cleaning?
SILVER
A motor’s disconnecting means usually need to be adequately rated to make or break the:
Locked Rotor Current
Copper contacts are good for high current, voltage and infrequent switching?
True or False?
TRUE
What are two purposes of the contact springs?
Reduce Bounce
Maintain Alignment
Temperature sensors measure temperature by sensing a change in a :
Physical characteristic
Thermocouples indicate temperature by producing a change in ________ .
Voltage
What are the two basic types of overcurrent devices?
Fuses
Circuit Breakers
A contactor armature PULLS IN at ______% of rated voltage
85%
What is the purpose of installing adder decks onto a relay?
To increase the number of contacts that can be controlled by the relay.
Is it desirable for a contactor to have high retentivity?
NO
High retentivity can force a contactor to stay shut.
Low-Voltage lighting relays utilize a _______ mechanism to return power to the lights after a failure(blackout)
Latching
