Starting Relays
Electrical Concepts
Current Relays
Potential Relays
Solid State Relays
100
This device removes the start winding from the circuit once the motor reaches speed.
Starting relay
100
The high current drawn when a motor first starts.
LRA (locked rotor amperage)
100
The normal position of current relay contacts.
Normally open (N.O.)
100
Normal state of contacts in a potential relay.
Normally closed (N.C.)
100
Material used in solid-state relays.
PTC material
200
The three main types of starting relays used in hermetic motors.
Current, potential, and solid-state relays
200
The normal running current of a motor.
FLA (full-load amperage)
200
The typical resistance of a current relay coil.
0-1 ohm
200
Typical resistance range of potential relay coils.
1000–10,000 ohms
200
What happens to resistance as the PTC heats up.
Increases
300
This relay operates using amperage draw.
Current relay
300
Voltage produced by the start winding that increases with motor speed.
Back EMF
300
What closes the contacts in a current relay at startup.
High current/magnetic field
300
The voltage required to energize the relay coil.
300
Cooling time required before restarting.
3-10 minutes
400
This relay operates using back electromotive force.
Potential relay
400
The condition when the rotor is not moving but power is applied.
Locked rotor condition
400
What causes the relay to open after startup
decreasing current
400
Voltage needed to keep the relay energized.
dropout voltage
400
Advantage of solid-state relays.
one relay covers multiple HP ranges
500
This type of relay uses PTC material to drop the start circuit.
Solid state relay
500
What happens to current as motor speed increases.
It decreases
500
A current relay coil reading high resistance indicates this.
a bad relay
500
The component that may remain in circuit if the relay fails.
starting capacitor
500
A visible sign of a failed solid-state relay.
burning or cracking