Also test shadows.For instance, there’s always two moneybags underneath the far end of this bridge, however one (magenta) is invisible. If we’ve two otherwise identical motors, one with a low Kv and one with a excessive Kv, then we are able to assume that the common magnetic area produced by the rotor magnets and the dimensions of the rotor itself (i.e. its radius and size) are the identical. The motor with fewer turns of wire may have a decrease induced voltage produced by the rotor ????????????????????? magnets as they cross by the tooth, giving it its excessive Kv ranking when in comparison with the motor with extra turns. You might simply as simply achieve a better torque output by buying a new motor controller with a higher current restrict and keeping your current motor unchanged. The issues begin when you employ a motor controller that outputs a present waveform which doesn’t exactly match the bEMF of your motor.
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The specific torque density of an electric motor (torque per unit volume) is unbiased of its Kv. A sinusoidal bEMF usually means a motor has been wound with distributed windings, the place the windings are distributed over many slots, and is extra common for big electric motors. The torque functionality of a BLDC motor is set by the common magnetic subject energy produced by the stator which acts on the rotor, the common magnetic subject energy produced by the rotor magnets which act on the stator and the dimensions of the rotor itself. 3. Reduce the flux gap distance between the rotor and the stator. 2. Replace the permanent magnets within the rotor with larger power density magnets. However, this assumption fails to take into consideration that the overall area of the copper windings is fastened and due to this fact the present density stays the same. Therefore, the only doable difference between our two motors can come from the common current density within the stator windings. This data was generated with GSA Content Generator Demoversion!
This leaves solely the common magnetic field energy produced by the stator as a attainable distinction. Let us take a look at just a single stator tooth and the affect that a different turn number can have on the utilized magnetic subject power when placed within the accessible winding area. The low Kv motor has 10 turns of wire each at four A, for the same total of 40A/tooth. Therefore these two motors will provide the same magnetic field power and have the same torque output. Similarly, the heat generated by an electric motor while producing a given torque worth can also be independent of Kv. Useful torque is produced by an electric motor whenever you feed in a present waveform to every section that completely opposes the a generated bEMF. However, this is essentially no completely different than growing the current in the low Kv motor with the identical finish consequence. Once you sum up the current contributions from each part for the sinusoidal waveform (PMSM) and for the trapezoidal waveform (BLDC) you see the identical outcome; an ideal fixed output present, and due to this fact a continuing output torque.
Most low-cost interest grade motor controllers (ESC’s) solely output a ‘six-step a hundred and twenty degree’ current waveform like that shown for the BLDC motor above. Which means that the current waveform produced by an ESC won’t ever completely match the bEMF of a BLDC motor. For instance, consider the torque produced by a PMSM and BLDC motor as seen by the determine below which were taken from James Mavey’s glorious masters thesis. Therefore, rewinding a motor to increase its Kv only is smart once you want to match the motor current draw to the present restrict of your current motor controller (ESC). As the ability dissipation within the motor scales with the sq. of the stator current, it feels only natural to assume that the low Kv motor, with its 4A current draw, will produce much less heat than our excessive Kv motor with its 10A current draw. Yes, you can enhance the present within the low Kv motor to be the same because the high Kv motor at 10A and produce more torque. However, for prime-efficiency purposes (e.g. multi-rotors used for cinematography, robotics and EV functions) the reduced noise, vibration and elevated effectivity that comes from utilizing a FOC motor controller with a PMSM might mean it’s value the extra funding.
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