How much heat comes from an electric motor
How much heat comes from an electric motor
(OP)
Hello.
If I have a 45kW 3-phase electric motor, can I estimate how much heat is generated from it?
For example, if I know that the power factor is 0.78, is it reasonable to assume all the inefficiencies eventually translate to heat? So that I can say about 10kW of heat is generated?
Thankyou.
Marko.
If I have a 45kW 3-phase electric motor, can I estimate how much heat is generated from it?
For example, if I know that the power factor is 0.78, is it reasonable to assume all the inefficiencies eventually translate to heat? So that I can say about 10kW of heat is generated?
Thankyou.
Marko.





RE: How much heat comes from an electric motor
The estimate of the motor heat dissipation from the motor efficiency can be derived too; however, the whole loss calculated over the efficiency is not RI^2, watts. Some of losses causing the efficiency to be lower than 1 are covering the windage, and rotor dynamics.
E.g., if the motor is 95% efficient, 45kW is used as a motor output, then 45kW/0.95 - 45kW=2.368kW are losses. If windage and dynamics consumes 2/3 than 1/3 is RI^2 heat dissipation, i.e. about .79kW.
RE: How much heat comes from an electric motor
RE: How much heat comes from an electric motor
For identifying the actual value of the following losses , testing and calculation is requred.
Windage & friction losses
No load magnetic & copper loss
Laod copper loss (stator & rotor)
RE: How much heat comes from an electric motor
I agree that a 45 kW motor will turn that 45kW of energy into some mechanical form.
For a 80% efficient motor, it will draw a total 55kW of energy.
So, that 10kW of energy left over after 45kW are converted to mechanical energy is the result of friction, resistance, slip etc. So generally, does most of this energy loss degrade to heat/noise? Or is only about 1/3 of it converted to heat? Is there a general 'rule of thumb' to estimate this heat loss?
Thankyou
RE: How much heat comes from an electric motor
The power factor doesn't play a role in heat loss determination because it doesn't directly relate to efficiency. In fact, extremely high efficiency motors have poor power factors.
RE: How much heat comes from an electric motor
The loss in the motor itself, the useful part of the energy
gets converted into mechanical energy first and finally --
in the external mechanism -- into heat.
<nbucska@pcperipherals.com>
RE: How much heat comes from an electric motor
RE: How much heat comes from an electric motor
RE: How much heat comes from an electric motor
Since the most stable form of energy is heat, all energy eventually gets converted into heat energy.
So froma HVAC load estimation point of view,the heat dissipation into the room is very much dependent on the system configuaration as explained in above example