Which type of motor typically has the lowest starting torque in HVACR systems?

The shaded-pole motor is known for having the lowest starting torque among the various types of motors used in HVACR systems. This is primarily due to its design, which employs a shading coil that creates a phase shift in the magnetic field, allowing the motor to start and run. However, the torque generated at startup is quite limited because shaded-pole motors have a low torque-to-power ratio.

They are typically used in applications where the load does not require high starting torque, such as in small fans and blowers. In comparison, other motor types like capacitor-start, split-phase, and permanent split capacitor motors are designed to provide greater starting torque, making them suitable for applications that require more power to overcome initial resistance.

Choosing the shaded-pole motor for certain applications is advantageous because it is simple and cost-effective, but it's primarily limited by its low starting torque, which precludes its use in situations where higher starting power is necessary.