Electric Motor Control Basics - Book - Page 42
Industrial Control Basics: Part 3, Starters
Standards and Ratings
There are many factors involved in motor starter ratings, such as thermal current,
continuous current, motor voltage, and power.
The thermal current is dependent on the thermal conductivity (k), which is the property
indicating the heat conducting ability of a material. It means that thermal current is
directly proportional to the thermal conductivity.
The continuous current, which is also commonly referred to as the continuous ampere
rating is a measure of the capability of the motor control starter to handle current for a
continuous time.
The power rating of the motor starter is based on the type of motor used. DC motor
starters have ratings for DC horsepower. On the other hand, AC motor starters have a
single-phase power and three-phase power rating.
The rating of the motor starter is based on the size and type of load for which it
was designed. Starters conform to the standards and ratings from Underwriters
Laboratories (UL), Canadian Standards Association (CSA), International
Electrotechnical Commission (IEC) and National Electrical Manufacturers Association
(NEMA).
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
42
