331 Flashcards
Jogging Circuits, Latching Relays, Alternating Relays, and Phase-Loss Relays
What is a Jogging Relay
This is a type of relay that allows you to move the motor shaft (inch it) only when you press the button.
What is a Latching Relay
This is a type of relay that is mechanically held unlike a standard relay that is electrically held.
What the Difference Between a Latching Relay and a Standard Relay
Latching relay needs it coil energized (for only a moment) to change to its normal state, and once power is reintroduced back to its coil it changes its state again. While a standard relay is already in its normal state but changes when its coil is energized
How does a Latching Relay Work
Power is introduced to its latch or operate terminal (only for a moment )and that causes it to change to its normal state. And to revert this change power has to be reintroduced to its reset or unlatched terminal.
What is Jogging also Called
Inching.
How Many Coils does a Latching Relay
I may come with 1 or 2 coils.
How would a Latching Relay Latch and Unlatch if it only has One Coil
It does this by using diodes to send positive or negative current to through the coil.
How do Diodes Work
They permit current to only flow in one direction and not the other.
What Line on a Latching Relay should the Common be Connected to the Avoid Damaging the Diode
The common should be tied on line 2 of the control circuit.
In what Situation Should a Latching Relay be Used
In locations with vibrations or a situation where you need to maintain connection during a power outage.
What is an Alternating Relay
This is a type of relay that automatically switches from powering one load to another.
What is Phase Loss
This is also called single phasing, its occurs when a phase is lost or disconnected.
What Protection do Phase Loss Monitors Provide
They protect against phase failure, undervoltage, phase reversal, and voltage unbalance. These are phase failure relays.
What are the Types of Phase Failure Relays
Motor protection system type and motor protection device type.
What are Some Features of the MPS
It is socket mounted, detects phase unbalance over 10%, has DPDT SB contacts, and undervoltage adjustment from 75%-100%.
How do MPD and MPS Reset
They reset automatically once the problem has been corrected.
What Control Wire System Would be Recommended for Phase Loss Relays (MPD/MPS)
Three Wire Control System.
What Happens if the MPS is Tapped from the Load Side
The contacts for the MPS wont close until the coil is energized. It must be in parallel to the coil
What Side would you Tap the MPS for a Reversing Circuit
Only on the line side. It must be in series with the coil.
