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Thanks very much for your detailed experimentation and explanation. The source of electric motor inefficiencies is a deep topic but one which I plan on exploring in this blog in more detail soon. However, keep in mind you will also be measuring the motor controller losses.Īs you mentioned, the power output is the angular velocity multiplied by the torque and from that you can find the efficiency. The easiest way to measure this power is before the motor controller where the current is still DC and the voltage is near constant. Refer to this post for more details: Īssuming a power factor of 1, the electrical power supplied to a motor is given by the voltage drop across the motor multiplied by the current supplied to the motor (P = VI). Kv x Supply voltage = maximum no load speed that a motor can achieve and not the motor speed at a given power output. I think I can see the problem with your assumptions. Operating a motor with 'six step 120 degree' commutation at low speed without a position sensor will result in less torque being produced than that predicted using the 'conversion constant' while high speed operation should be pretty close.Įlectric motors can indeed have an efficiency >95%.
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This is generally true when using field oriented control (FOC) on a PMSM motor that has inbuilt position sensors (hall effect, encoder etc.).
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the current is not exactly on the q-axis at all times).