This article compares three schemes of fan control used on large air conditioning and refrigeration condensers. The first scheme is step control; the second is a hybrid with a VFD on only one bank of ...

A Variable Frequency Drive (VFD) regulates the speed of a 3-phase AC electric motor by controlling the frequency and voltage of the power it delivers to the motor. These devices, also known as ...

All questions and answers are based on the 2011 NEC. Q. What is the Code rule for motor control circuit overcurrent protection? A. Motor control conductors that aren’t tapped from the branch circuit ...