Rockwell Automation 1336T Wiring and Grounding Guide, (PWM) AC Drives - Manual (Page 47)

Rockwell Automation Publication DRIVES-IN001M-EN-P - March 2014 47
Power Distribution Chapter 2
DC Bus Connections
For reliable system operation, minimize the interconnection of drives to the DC
bus and the inductance levels between the drives. Use a low inductance-type DC
bus (for example, 0.35 μH/m or less).
Figure 13 - Star Configuration of Common Bus Connections
Bus Bar Versus Cable
Follow these recommendations for using a bus bar versus a cable:
• A DC bus bar is recommended versus a cable.
• When a DC bus bar cannot be used, follow these guidelines for DC bus
cables:
–
Use twisted cable where possible, approximately one twist per inch.
– Use cable rated for the equivalent AC voltage rating. The peak AC
voltage is equivalent to the DC voltage. For example, the peak AC
voltage on a 480V AC system no load is 480 x 1.414 = 679V peak. The
679V peak corresponds to 679V DC at no load.
IMPORTANT Do not daisy chain the DC bus connections. Configure the DC bus connections in
a star configuration to allow for proper fusing.
L1
L2
L3
DC+
DC+
DC-
DC-
BR1 BR2
M1
L1 L1
L2 L2
L3 L3
DC+ DC- BR1 BR2
M2
L1
L2
L3
DC+ DC- BR1 BR2
M3
DC- DC+
Bus Supply
Power Distribution Terminal Block
AC Drive AC Drive AC Drive