Electrical Motor Heat Loss
Reference data and engineering information about electrical motor heat loss for electrical applications.
electricalmotorheatlossCalculator
Overview
Engineering reference data for Electrical Motor Heat Loss in electrical engineering.
Key Formulas
Ohm's Law
Voltage = Current × Resistance.
Power
Electrical power.
Energy
Energy = Power × Time.
Variables
| Symbol | Description | Unit |
|---|---|---|
| Voltage | V | |
| Current | A | |
| Resistance | Ω | |
| Power | W |
Data Tables
4 rows
Size of Motor(kW) | Efficiency(%) | Heat Loss(watts/kW) |
|---|---|---|
| 0 - 2 | 75 | 250 |
| 3 - 15 | 85 | 150 |
| 15 - 150 | 90 | 100 |
| 150 - | 92 | 80 |
Source: engineeringtoolbox.com
3 rows
Nameplate Rating(hp) | Motor Efficiency(%) | Motor in Room, Driven Device inside Room(Btu/hr per rated hp) | Motor in Room, Driven Device outside Room(Btu/hr per rated hp) | Motor outside Room, Driven Device inside Room(Btu/hr per rated hp) |
|---|---|---|---|---|
| 0 - 1.5 | 80 | 2542 | 508 | 2034 |
| 1.5 - 12.5 | 85 | 2542 | 381 | 2161 |
| 12.5 - | 90 | 2542 | 254 | 2289 |
Source: engineeringtoolbox.com
Heat Transfer to Room Air
The heat transferred to a room or enclosure depends on the relative location of the electric motor and the driven device:
- Motor and driven device in the room: All electrical energy supplied to the motor is eventually converted to heat in the room, including motor heat loss and frictional energy from the driven device.
- Motor in the room, driven device outside the room: Only the heat loss from the motor is transferred to the room. Frictional energy from the driven device is dissipated outside.
- Motor outside the room, driven device inside the room: Frictional loss from the driven device is transferred to the room. Motor heat loss is dissipated outside.
If the motor and mechanical equipment are in the same room or enclosure, all supplied electrical energy converts to heat, increasing the room temperature.
Example Calculation
For a motor supplied with 10 kW of power, using the heat loss value of 150 watts/kW (from the 3-15 kW motor range in the table):
\text{Heat Loss} = (10 \, ## Interactive Charts <InteractiveChart columns={[ { key: "size", label: "Size of Motor", type: "string", unit: "kW" }, { key: "efficiency", label: "Efficiency", type: "number", unit: "\%" }, { key: "heatLoss", label: "Heat Loss", type: "number", unit: "watts/kW" } ]} rows={[ { size: null, efficiency: 75, heatLoss: 250 }, { size: null, efficiency: 85, heatLoss: 150 }, { size: null, efficiency: 90, heatLoss: 100 }, { size: null, efficiency: 92, heatLoss: 80 } ]} xKey="size" title="Heat loss from electric motors due to inefficiency" source="engineeringtoolbox.com" /> <InteractiveChart columns={[ { key: "efficiency", label: "Motor Efficiency", type: "number", unit: "\%" }, { key: "heatLossInside", label: "Motor in Room, Driven Device inside Room", type: "number", unit: "Btu/hr per rated hp" }, { key: "heatLossOutside", label: "Motor in Room, Driven Device outside Room", type: "number", unit: "Btu/hr per rated hp" }, { key: "heatLossMotorOut", label: "Motor outside Room, Driven Device inside Room", type: "number", unit: "Btu/hr per rated hp" } ]} rows={[ { efficiency: 80, heatLossInside: 2542, heatLossOutside: 508, heatLossMotorOut: 2034 }, { efficiency: 85, heatLossInside: 2542, heatLossOutside: 381, heatLossMotorOut: 2161 }, { efficiency: 90, heatLossInside: 2542, heatLossOutside: 254, heatLossMotorOut: 2289 } ]} xKey="efficiency" title="Heat loss to room air from electric motors based on location of motor and driven device" source="engineeringtoolbox.com" /> ## References - [Original Source](https://www.engineeringtoolbox.com/electrical-motor-heat-loss-d_898.html)