Standard Handbook of Plant Engineering, Third Edition
Packed with tables, formulas, charts, graphs, and checklists, this guide offers you the cutting-edge information you need to keep your plant operating at peak efficiency and profitability.
TABLE OF CONTENTS Standard Handbook of Plant Engineering, Third Edition
Chapter 5.7: Electric Motors
John C. Andreas
Consultant
MagneTek
St. Louis, Missouri
GLOSSARY OF COMMON MOTOR TERMS
- Ambient temperature
- The temperature of the surrounding cooling environment.
- Amperes
- The unit of intensity of electric current flowing in a conductor produced by the applied voltage.
Full-load amperes (FLA): The current drawn by the motor when the motor is delivering its rated horsepower at its rated speed (full-load speed) and with rated voltage and frequency applied to the motor.
Locked-rotor amperes (LRA) (starting current per ampere): The current drawn by the motor with the rotor locked (zero speed) and with rated voltage and frequency applied to the motor.
Service-factor amperes (SFA): The current drawn by the motor when the motor is delivering its service-factor horsepower with rated voltage and frequency applied to the motor.
- Efficiency
- How well a motor turns electric energy into mechanical energy, expressed as the ratio of mechanical power output (watts) to electric power input (watts).
Alternatively, efficiency may be defined as
But
- Frequency
- The number of complete cycles of current per second made by alternating current. While sometimes called cycles per second, the preferred terminology is hertz. The standard frequency in the United States is 60 Hz; however 50 and 25 Hz can be found in the United States as well as in other industrial nations.
- NEMA
- The National Electrical Manufacturers Association (NEMA), an organization which establishes voluntary standards and represents general practice in industry. NEMA has defined motor standards that include nomenclature, construction, dimensions,...
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