The boot time was measured from the point of applying 24V control power to the drives. The time was measured to specific indicators and functions of the drives.
Note that AC power was already turned on prior to running these tests, so that the drives could automatically enable. Normally, AC power would be applied after the drives are booted up, and the enable signal would be applied after the drives are “Ready to Operate.” (See the timing diagrams in the installation manuals.) But for the sake of taking time measurements without the use of a PLC or control relays, the drives needed to automatically enable after booting up.