Electric Motor Control Basics - Book - Page 62
Applying Motor Control in a Wastewater Application
4. Direct-On-Line (DOL) Motor Starter:
As the name suggests, these devices are used to start electric motors of pumps
and other electronic devices such as compressors, conveyor belts, and fans. A
motor starter features various electronic and electro-mechanical devices such as
a contactor paired with a motor protection circuit breaker or an overload relay.
DOL starters are used to start small water pumps because they provide several
advantages such as 100% torque during starting, simplified control circuitry, easy
installation and maintenance, and minimal wiring. Enclosed DOL Motor Starters are
also an option, where the entire starter assembly is placed inside an enclosure.
Industrial Control
Basics:
Part 1, Contactors
5. Programmable Logic Controller (PLC):
The programmable logic controller or PLC is really an industrialized computer that
operates without a keyboard or monitor. Originally, the PLC was a replacement for
large panels of relays that switched on and off, controlling a machine operation. The
programming language of the PLC mimicked the Relay Logic, making the transition
from relays to PLC’s an easy to understand process. Today’s PLC’s offer much more
complex operational capabilities and communications via Ethernet or proprietary
networks. The ability to control multiple pumps in a coordinated fashion makes PLC’s
a common component of water management systems.
The Benefits of Type E/F
Motor Protection
Circuit Breakers
6. Variable Frequency Drive (VFD):
They’re used for running an AC motor at variable speeds or to ramp up speed for
smoother start up. VFD’s control the frequency of the motor to adjust the pump
motor RPM’s. VFD’s are widely used to regulate water flow at a water treatment
plant, allowing more control over the flow of the pump.
Industrial Control
Basics: Part 2,
Overload Relays
Industrial Control
Basics: Part 3,
Starters
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
62
