All VFD's for motors larger than 5 HP, and/or on systems serving critical loads, include full maintenance bypass systems as an option. These bypasses are configured to allow operation of the motor in 'across the line' mode while the drive is being repaired. Also, the bypass equipment is designed to be electrically isolated from the VFD drive equipment so that maintenance may be safely done with the motor running 'across the line' in through the bypass.

The electrical system serving a VFD, and the mechanical system being served by the VFD,

are sized and braced to allow the motor (and associated mechanical system) to start and

operate properly and safely when in the bypass mode - across the line. Special attention

is given to the affects of the voltage drops during start and the ability of the upstream over current devices to carry the locked rotor current during the startup.