Rockwell Automation SA500 DC Bus Supply - Manual (Page 16)

3-2 SA500 DC Bus Supply
3.1 Selecting a DC Bus Supply
The number of SA500 AC Power Modules that a single DC bus supply can power
depends upon the bus supply’s current rating and the combined current draw of the
attached motors.
Use the following procedure to select a bus supply based on motor current values.
Refer to Appendix C for motor current information on Industrial Brushless, Brushless
Servo, and Induction motors.
Step 1. Add together the continuous Idc currents of all the motors to be powered
from the bus supply. See Appendix C.
Step 2. If all of the motors can accelerate, decelerate, or overhaul (draw maximum
current) at the same time, add together the maximum Idc currents of the
motors. See Appendix C.
If only some of the motors can accelerate, decelerate, or overhaul at the
same time, add their maximum Idc currents to the continuous Idc currents of
the other motors to obtain a total maximum Idc current.
Step 3. Select the DC bus supply based on both Idc continuous current and Idc
maximum current. See table 3.1 for bus supply ratings.
Note that regardless of the total current drawn by the motors, the maximum
number of SA500 AC Power Modules that can be powered from a single DC
bus supply is six.
If the motors are to be operated in the regenerative mode, the applications’s
regenerative power dissipation requirements should be evaluated. The power
dissipation capabilities of the bus supplies with internal braking resistors are shown in
table 3.1. Refer to table 3.5 for the resistance values of the internal braking resistor(s).
If the application’s requirements exceed these values, refer to section 3.2 for
information on selecting external braking resistors.
Table 3.1 – SA500 DC Bus Supply Motoring Current and Internal Power Dissipation Specifications
DC Bus Supply
Output Rating
Continuous
Current
(Idc) RMS
Output Rating
Maximum
Current
(Idc) RMS 1
1. 10 second overload
Internal Braking Resistor
Maximum Power Dissipation
Continuous 2
2. Maximum continuous braking power = (continuous fuse current) 2 x R, where continuous fuse current = 0.9 x fuse rating.
0.5 Second 3
Overload
3. Maximum 0.5 second overload braking power = (maximum fuse current) 2 x R, where maximum fuse current = 2 second fuse melting
current.
Turn-On
Voltage 4
4. V
LL
x 1.47 + 5 volts, where V
LL
is 230V
AC
nominal.
615055-2R
50A 150A 414W 5
5. Snubber Fuse Limited
1568W 5 343V
615055-2S
615055-2T
100A 450A 1200W 6
6. Resistor Limited
4624W 6 343V
615055-2V