Technical information

24
230V FX Series Positioning Drive Reference Manual
to the drive will drop under heavy load conditions. This will decrease the available maximum
speed of the drive.
If your machine parameters change after the initial sizing such that a motion profile requires
more than the original average torque, you should review the transformer size to be sure that
it is adequate.
Example 1: FX-455 (single phase)
From the FX-455 torque speed curves in the “Specifications” section with a 230VAC input,
the maximum torque available at the maximum speed is 41.25 lb-ins at 3000 RPM. Using
these figures in the first formula:
3000 x 41.25 x 0.018/1000 = 2.23 KVA (single phase)
In this case, a 3.0 KVA transformer would be selected.
Example 2: FX-4120 (4120 three phase)
Again, from the FX-4120 torque speed curves in the “Specifications” section with a 230VAC
input, the maximum torque available at the maximum speed is 90 lb-ins at 3000 RPM. Using
these figures in the second formula:
3000 x 90 x 0.01182/1000 = 3.2 KVA (3 phase)
In this case, a 4.0 KVA transformer would be selected.
Example 3: Multiple Axis
For multiple axis transformer sizing, you need to determine the torque and speed
requirements for each axis. The two examples shown below cover two possible cases. Both
FX drives draw current from a 230VAC supply transformer at the same time. One FX-490
drive operates at 80 lb-ins at 2000 RPM and an FX-4120 operates at 100 lb-ins at 2500 RPM.
Enter the values into the formula:
[FX-490] 2000 RPM x 80 lb-ins x 0.01182/1000 = 1.9 KVA
[FX-4120] 2500 RPM x 100 lb-ins x 0.01182/1000 = 2.95 KVA
Total KVA required = 1.9 + 2.95 = 4.85 KVA
In this example a 5 KVA transformer is selected.
The sizing examples above assume that no other components are attached to the same
transformer.