Electric Motor Control Basics - Book - Page 3
Industrial Control Basics:
Part 1, Contactors
Introduction
A contactor is an electrical device which is used for switching an electrical circuit on or
off. It is considered to be a special type of relay. However, the basic difference between
the relay and contactor is that the contactor is used in applications with higher current
carrying capacity, whereas the relay is used for lower current applications. Contactors
can be field mounted easily and are compact in size. Generally, these electrical devices
feature multiple contacts. These contacts are in most cases normally open and provide
operating power to the load when the contactor coil is energized. Contactors are most
commonly used for controlling electric motors.
There are various types of contactors, and each type has its own set of features,
capabilities, and applications. Contactors can break current over a wide range of
currents, from a few amperes to thousands of amperes, and voltages from 24 VDC
to thousands of volts. In addition, these electrical devices come in varying sizes, from
hand-held dimensions to sizes measuring a meter or yard on one side (approximately).
The most common application area of the contactor is high-current load. Contactors
are known for their capability to handle currents of over 5000 amperes and high power
over 100 kW. Heavy motor currents produce arcs when being interrupted. These arcs
can be reduced and controlled using a contactor.
Industrial Control
Basics:
Part 1, Contactors
Industrial Control
Basics: Part 2,
Overload Relays
Industrial Control
Basics: Part 3,
Starters
The Benefits of Type E/F
Motor Protection
Circuit Breakers
Basic Pump Control:
Three Phase DOL Starter
Control of an Electric Pump
Applying Motor Control
in a Wastewater
Application
NEMA vs IEC Motor
Controls
Understanding
IP Ratings
03
