Hvac School - For Techs, By Techs

Bryan lays down some motor speed facts in about 10 minutes in this short podcast episode. We can figure out how quickly a single-phase motor (PSC) will run if we understand how many cycles it will make per second. In the USA, the standard hertz is 60 Hz (60 rotations or magnetic alternations per second). Motors are inductive loads that create an electromagnetic field with a spinning rotor and stationary stator; the amount of poles on the stator determines how quickly the rotor spins (RPM). In the RPM counts, there are some allowances for slip. Slip varies depending on the load, with excessive loads causing more slip. Some multi-tap blowers have additional winding resistance and decreased current (due to the extra taps), which increase the slip. The rated load RPM usually accounts for the RPM at high speed, not medium or low speed with added resistance. On the other hand, variable-speed motors or ECMs are powered by a variable frequency (sometimes a variable frequency drive or VFD). The motor control takes the