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

Electrical Motors - Heat Loss

Heat loss from an electrical motor to the surroundings.

Heat Loss from Electric Motors during Operation

Heat loss from electric motors due to inefficiency:  

Electrical Motors - Heat Loss vs. Efficiency
Size of Motor
(kW)		Efficiency
(%)		Heat Loss
(watts/kW)
0 - 2 75 250
3 - 15 85 150
15 - 150 90 100
150 - 92 80
  • 1 kW = 1.34 hp
  • 1 hp = 0.746 k W

Example - Heat Loss from an Electric Motor

The heat loss from an electric motor supplied with 10 kW can with the heat loss 150 watts/kW from the table above be calculated as

(10 kW) (150 watts/kW)

= 1500 watts

= 1.5 kW

The rest of the energy

(10 kW) - (1.5kW)

= 8.5 kW

is output mechanical energy. 

If the motor and the mechanical equipment connected to the motor is in the same room - or enclosure - all electric energy supplied to the motor will convert to heat and temperature increase in the room.

Heat Loss from an Electric Driven Device to a Room

The heat transferred to a room or enclosure depends on the location of the motor and the driven device related to the room. 

  1. motor and driven device in the room - all energy to the motor is at the end transferred to the room (heat loss from the motor and frictional energy from the driven device)
  2. motor in the room and device outside the room - only heat loss from the motor is transferred to the room - frictional energy from the driven device is lost outside the room
  3. motor outside the room and device inside the room - frictional loss from the driven device is transferred to the room - energy loss from the electric motor is lost outside the room
Electrical Motors - Heat Loss to Room Air
Nameplate Rating
(hp)		Motor Efficiency
(%) 		Heat Loss to Room Air
(Btu/hr per rated hp)
Motor in Room
Driven Device inside Room		Motor in Room
Driven Devise Outside Room		Motor Outside Room
Driven Device inside Room
0 - 1.5 0.80 2542 508 2034
1.5 - 12.5 0.85 2542 381 2161
12.5 - 0.90 2542 254 2289
  • 1 Btu/h = 0.293 W 
  • 1 horsepower = 2542 Btu/hr

Related Topics

  • Electrical

    Electrical engineering with units, amps and electrical wiring. Wire gauges, electrical formulas, motors and more.

Related Documents

Search

Search is the most efficient way to navigate the Engineering ToolBox.

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 older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

Citation

This page can be cited as

  • The Engineering ToolBox (2005). Electrical Motors - Heat Loss. [online] Available at: https://www.engineeringtoolbox.com/electrical-motor-heat-loss-d_898.html [Accessed Day Month Year].

Modify the access date according your visit.

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!

Unit Converter

















































8.21.8

.