Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Electrical Motors - Locked Rotor Design Code Letters

NEMA locked rotor indicating code letters for electrical motors.

Sponsored Links

NEMA - The National Electrical Manufacturer's Association - who sets the design standards for motors, has established a NEMA Code letter designation to classify motors by the ratio of locked rotor kVA per horsepower.

NEMA
Code Letter
kVA/HP
with locked rotor
Approximate Mid-Range Value
A 0 - 3.14 1.6
B 3.15 - 3.55 3.3
C 3.55 - 3.99 3.8
D 4.0 - 4.49 4.3
E 4.5 - 4.99 4.7
F 5.0 - 5.59 5.3
G 5.6 - 6.29 5.9
H 6.3 - 7.09 6.7
J 7.1 - 7.99 7.5
K 8.0 - 8.99 8.5
L 9.0 - 9.99 9.5
M 10.0 - 11.19 10.6
N 11.2 - 12.49 11.8
P 12.5 - 13.99 13.2
R 14.0 - 15.99 15.0
S 16.0 - 17.99  
T 18.0 - 19.99  
U 20.0 - 22.39  
V 22.4 - and up  

The starting kVA required by a motor starting at full voltage is determined from the nameplate on the motor or from the manufacturer.

In general it is accepted that small motors requires higher starting kVA than larger motors. Standard 3 phase motors often have these locked rotor codes:

  • less than 1 hp: Locked Rotor Code L, 9.0 - 9.99 kVA
  • 1 1/2 to 2 hp: Locked Rotor Code L or M, 9.0 - 11.19 kVA
  • 3 hp : Locked Rotor Code K, 8.0 - 8.99 kVA
  • 5 hp : Locked Rotor Code J, 7.1 - 7.99 kVA
  • 7.5 to 10 hp : Locked Rotor Code H, 6.3 - 7.09 kVA
  • more than 15 hp : Locked Rotor Code G, 5.6 - 6.29 kVA
Sponsored Links

Related Topics

Related Documents

Sponsored Links

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

Translate
About the Engineering ToolBox!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.

Citation

This page can be cited as

  • Engineering ToolBox, (2005). Electrical Motors - Locked Rotor Design Code Letters. [online] Available at: https://www.engineeringtoolbox.com/locked-rotor-code-d_917.html [Accessed Day Mo. Year].

Modify access date.

. .

close

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

3 30

Sponsored Links
.