Industrial Engineer · phase 9 of 16 · noun

Horsepower / Kilowatt Rating

Nominal motor-power class for the drive, secondary to verifying motor current, duty, voltage, and overload requirements.

The Explain card

Plain English
The horsepower or kilowatt rating is the nominal motor size the drive is meant for. It is a convenient label, and the drive itself only knows about volts and amps.
Example
A 10 horsepower drive is offered for a 10 horsepower motor. If that motor is a high efficiency design with unusual current, or runs constant torque with heavy overloads, the 10 horsepower drive may be too small.
Why it matters
Sizing by horsepower alone is the classic way to under size a drive, because the label assumes a typical motor on a typical variable torque load. The current rating, the duty rating and the environment decide, and the horsepower on the box only gets you to the right shelf.
Hook
A label for the catalog, never a specification for the motor.

Word knowledge

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

During commissioning, the technician compares the motor nameplate horsepower with the drive selection sheet before entering the motor data.

How it is built
  • horse compound element the animal historically used as the comparison standard
  • power compound element capacity for performing work
Where it came from
Origin
an English compound of horse and power, associated with James Watt's comparison of steam engines with working horses
Entered the language
1806
What changed
It moved from a practical engine comparison to a standardized unit name and then to a familiar nameplate and equipment-rating term.
How it is spelled
Pattern
It is written as a closed compound of two complete English words.
Pattern
The final e in horse remains when horse joins power.
Breaks the pattern
Older texts often spell it horse-power with a hyphen.

Spelled like

  • firepower
  • manpower
  • waterpower
Broken into chunks
  • horse
    • horseman
    • horseshoe
  • power
    • powerful
    • powerhouse
What it sits beside

Same subject

  • kilowatt rating
  • motor nameplate
  • full-load amperes
  • variable frequency drive

Same shape

  • firepower
  • manpower
  • waterpower

motor nameplate entries

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.

Neighbours in this phase