Formula to calculate torque of bldc motor
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Connect the BLDCM to load and run at any given speed.
Measure Vdc, Idc and N (rpm).
Get machine efficiency*.
Use following formula to compute approximate torque.
Power Input (kW), Pi=Vdc∗IdcPi=Vdc∗Idc
Power Output (kW), Po=2πNTl60Po=2πNTl60
Efficiency, η=PoPiη=PoPi
Substituting & rearranging the terms leads to-
Load torque (Nm), Tl=ηPi602πNTl=ηPi602πN
The above computations will provide approximate value of load torque in absence of a reliable torque sensor.
PMBLDC Machine’s efficiency may be obtained from manufacturer datasheets or may be assumed somewhere between 75%~90%. Take care while making an assumption. e.g. I’d take 85% ( = 0.85) efficiency for a low-power machine made by a standard manufacturer, but it may not be true for a non-standard manufacturer.
cheers !!!
Measure Vdc, Idc and N (rpm).
Get machine efficiency*.
Use following formula to compute approximate torque.
Power Input (kW), Pi=Vdc∗IdcPi=Vdc∗Idc
Power Output (kW), Po=2πNTl60Po=2πNTl60
Efficiency, η=PoPiη=PoPi
Substituting & rearranging the terms leads to-
Load torque (Nm), Tl=ηPi602πNTl=ηPi602πN
The above computations will provide approximate value of load torque in absence of a reliable torque sensor.
PMBLDC Machine’s efficiency may be obtained from manufacturer datasheets or may be assumed somewhere between 75%~90%. Take care while making an assumption. e.g. I’d take 85% ( = 0.85) efficiency for a low-power machine made by a standard manufacturer, but it may not be true for a non-standard manufacturer.
cheers !!!
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