Industrial Engineer · phase 9 of 16 · noun
Motor Efficiency
Ratio of mechanical output power to electrical input power at a stated operating point.
The Explain card
- Plain English
- Efficiency is the fraction of the electrical power going into the motor that comes out of the shaft as mechanical power. The rest is heat in the windings, the iron and the bearings.
- Example
- A 20 horsepower motor rated 93 percent efficient draws about 16 kilowatts at full load and turns about 15 of them into work. The other kilowatt warms the frame.
- Why it matters
- Efficiency sets how much heat the motor has to shed, which matters more at low speed on a drive, where the shaft mounted fan slows down with it. It is also the number that decides whether a drive retrofit pays for itself.
- Hook
- The gap between what you buy and what you get.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During commissioning, the engineer compares motor efficiency at rated load with the nameplate value before accepting the variable frequency drive setup.
Why these words
- motor Latin motor, mover, from movere, to move identifies the machine whose performance is being discussed
- efficiency Latin efficientia, efficacy or productive power names the measured performance quality attributed to the motor
Where it came from
- Origin
- English compound formed from motor, through Latin motor, and efficiency, through Latin efficientia
- Entered the language
- late 19th century
- What changed
- Motor narrowed from a general mover to a power-producing machine, while efficiency developed from effective agency into a technical performance measure.
How it is spelled
- Pattern
- motor keeps the common Latin agent-noun ending -or
- Pattern
- efficiency changes the adjective ending -ent in efficient to the noun ending -ency
Spelled like
- actor
- generator
- proficiency
- sufficiency
Broken into chunks
-
mot
- motion
- motive
-
effici
- efficient
- efficiently
-
ency
- frequency
- proficiency
What it sits beside
Same subject
- rated load
- power factor
- motor nameplate
- variable frequency drive
- motor losses
Same shape
- pump efficiency
- drive efficiency
- system efficiency
motor performance terms
- motor efficiency
- power factor
- rated torque
motor loss sources
- copper loss
- core loss
- friction loss
Where it sits in the deck
Phase 9: VFD Ratings, Sizing, and Motor Data
Nameplate arithmetic, where the currents, voltages and duty ratings decide whether a drive can actually run the motor you bolted it to.
