The correct answer is: C. 85 to 95%.
A synchronous motor is an AC electric motor that rotates at a constant speed regardless of the load on the motor. This is because the speed of a synchronous motor is synchronized with the frequency of the AC power supply. Synchronous motors are used in a variety of applications, including fans, pumps, and compressors.
The efficiency of a synchronous motor is typically in the range of 85 to 95%. This means that for every 100 watts of power input to the motor, 85 to 95 watts of power are converted into mechanical output power. The remaining 5 to 15 watts of power are lost as heat.
The efficiency of a synchronous motor is affected by a number of factors, including the design of the motor, the quality of the materials used, and the operating conditions. The efficiency of a synchronous motor can be improved by using high-quality materials, by designing the motor for minimum losses, and by operating the motor at the correct speed and load.
Option A is incorrect because the efficiency of a properly designed synchronous motor is typically much higher than 60 to 70%.
Option B is incorrect because the efficiency of a properly designed synchronous motor is typically much higher than 75 to 80%.
Option D is incorrect because the efficiency of a properly designed synchronous motor is typically much lower than 99 to 99.5%.