Question

In a BLDC motor, if the Kv rating is increased while the propeller size remains constant, what is the immediate effect on the torque produced at the same voltage level?

Accepted Answer

In a BLDC motor, the Kv rating represents the motor&#x27;s velocity constant, defined as the number of revolutions per minute the motor spins per volt of input without a load. When you increase the Kv rating while keeping the voltage and propeller size constant, the torque produced at the same voltage level decreases. This occurs because Kv is inversely proportional to the torque constant of the motor. A motor with a higher Kv rating has fewer turns of wire in its stator coils, which reduces the motor&#x27;s magnetic strength and its ability to generate rotational force, or torque, for a given amount of electrical current. Because the propeller acts as a load that resists spinning, a motor with a higher Kv requires significantly more current to overcome that resistance; however, at the same voltage level, the motor cannot draw the extra current needed to maintain the same torque level as a lower Kv motor. Consequently, the motor produces less torque, often resulting in lower efficiency and a higher likelihood of overheating if the propeller load is too heavy for the motor&#x27;s internal resistance.

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In a BLDC motor, if the Kv rating is increased while the propeller size remains constant, what is the immediate effect on the torque produced at the same voltage level?