. VFD controls the motor speed varying the
frequency and voltage applied the motor. has several categories marks based upon the type
of product tested. Products that pass tests can carry UL
mark. Sometimes referred ultrasonic
proximity switch. develops standards and tests
products for safety.
Solid State Breaker
Solid State
Tripping Unit
Trip
Signal Magnetic
Latch
Breaker
Mechanism
Protected
Circuit
Power
Source
Current
Sensors
True Power Also called real power, true power the power dissipated by
circuit resistance. Shortened from volt-ampere
reactive.
Sonar Proximity Switch type sensing switch that uses high frequency sound to
detect the presence object without coming into contact
with the object.
Target
Emitted Pulse
Echo
Sonar
Proximity
Switch
Underwriters Laboratories independent product safety certification organization,
(UL) Underwriters Laboratories, Inc.
Variable Frequency Drive electronic device used control the speed AC
(VFD) motor.True power also equal the apparent power multiplied
by the power factor.
Var The basic unit for reactive power. Many circuit breakers use thermal-magnetic
or magnetic-only trip unit. Also called AC
drive. Other circuit breakers have solid-
state trip unit with multiple adjustments custom fit the circuit
breaker’s time current curve the application.True power equal I
2
R and measured in
watts.39
Trip Unit The part the circuit breaker that determines when the
breaker will trip
