SMAC
LAC-26 Technical Reference Manual
4/29/2013 71
The power supply current rating is based on the maximum current that will be required by the system. If the
power supply powers more than one drive, then the current requirements for each drive should be added
together. Due to the nature of servo drives, the current into the drive does not always equal the current out
of the drive. However, the power in is equal to the power out. Use the following equation to calculate the
power supply output current, IPS, based on the motor current requirements.
Use values of V and I at the point of maximum power in the move profile (when VMIM = max). This will
usually be at the end of a hard acceleration when both the torque and speed of the motor is high.
V
M
?
I
M
I
PS
=
-----------------------------
V
PS
?
(
0.98
)
Where:
PS
V
M
-nominal power supply voltage
I
M
-motor current
V
-motor voltage
