Electric Motor Control Basics - Book - Page 35
Industrial Control Basics: Part 3, Starters
The direct-on-line starter is the simplest form of motor starter, other than a manual
starter. The controller of this starter is typically a simple push button (but could be a
selector switch, limit switch, float switch, etc.). Pressing the start button closes the
contactor (by energizing the contactor coil) connected to the main supply and motor.
This provides the supply current to the motor. To turn the motor off, a stop button
is provided. To protect it from over current, the control circuit is wired through a
normally closed auxiliary contact of the overload relay. When the overload relay trips,
the normally closed auxiliary contact opens, and de-energizes the contactor coil, and
the contactor main contacts open.
The Advantages of Using Direct-On-Line Motor Starters:
• They have a compact design.
• They are cost-effective.
• They have a simple construction.
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
35
