Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive - Air-Cooled (A Frame) - Manual (Page 74)

2-44 Drive Installation
7000A-RM001A-EN-P – January 2011 7000 “A” Frame
Identification of Types of Electrical Supplies – Grounded and
Ungrounded Systems
When dealing with an ungrounded, three-phase electrical supply
system, the cable insulation must be capable of handling not only the
phase to phase voltage, but also the voltage to ground if one of the
other phases develops a ground fault. In practice, the cable
insulation of an ungrounded, three-phase system must be good for at
least a continuous voltage of root three (1.732) times (1.1) times the
rated voltage of the supply. (1.732 x 1.1 = 1.9 times the rated line-
to-line voltage)
Ground Bus
The drive ground bus runs along the top of the drive at the front.
The ground bus is accessible at the top of each of the drive
enclosures when the enclosure door is opened (and the low voltage
compartment hinged out in the case of the DC link/fan cabinet). It is
the responsibility of the installer to ensure that the drive is grounded
properly, typically at the point on the ground bus in the cabling
cabinet, close to the line cable terminations.
Interlocking Access to the medium voltage areas of the drive is restricted by the
use of key interlocking for safety.
At installation the key interlocking is set up so that access to the
medium voltage compartments of the equipment can only be made
when the upstream power is locked in the off position.
Additionally, the key interlocking prohibits the upstream power
being applied until the medium voltage drive’s access doors have
been closed and locked shut.
It is the responsibility of the installer to ensure that the key
interlocking is installed properly to the upstream equipment.