Electric motors can achieve the same propulsive power as combustion engines with significantly lower shaft power. The reason lies in the different torque curves of electric motors and petrol engines. While the torque curve of combustion engines features a prominent peak, with maximum torque being available only over a limited engine speed range, electric motors feature a much flatter torque curve with ample torque available at any engine speed.
With this type of motor, the ratio of the motor speed to the frequency of supply voltage is constant. As a rule, synchronous motors are torque controlled. They therefore always draw as much current as they need in order to deliver the necessary torque at the desired motor speed. For this reason they are the preferred choice for use in fields with especially demanding torque requirements. If the motor needs more power to maintain a given propeller speed it will automatically draw more current.