Rockwell Automation 20Y PowerFlex Active Front End - Manual (Page 152)

152 Rockwell Automation Publication 20Y-UM001E-EN-P - July 2014
Appendix C Application Notes
Advanced Procedure to Size the AFE
1. Convert all motor powers to kW (kW = HP x 0.746).
2. Determine the total power and input current required during
acceleration.
(1)
For Motoring Loads: P
Drive
= P
Motor
/ Motor Efficiency
For Regenerating Loads: P
Drive
= P
Motor
* Motor Efficiency
P
Accel
= P
Drive1
+ P
Drive2
+ …
Calculate the input current required on the regenerative unit during
acceleration, taking advantage of the 110% for 1 minute overload rating of
the regenerative unit.
I
Input
= P
Accel
x 1000 / (
√ 3 x V
LL
x 1.1),
where P
Accel
is in kW, and V
LL
= RMS line-to-line AC input voltage.
3. Determine the total power and input current required during steady-state
run operation.
(1)
For Motoring Loads: P
Drive
= P
Motor
/ Motor Efficiency
For Regenerating Loads: P
Drive
= P
Motor
* Motor Efficiency
P
Run
= P
Drive1
+ P
Drive2
+ …
Calculate the steady-state input current required on the regenerative unit.
I
Input
= P
Run
x 1000 / ( √ 3 x V
LL
),
where P
Run
is in kW, and V
LL
= RMS line-to-line AC input voltage.
4. Determine the total power and input current required during
deceleration.
(1)
For Motoring Loads: P
Drive
= P
Motor
/ Motor Efficiency
For Regenerating Loads: P
Drive
= P
Motor
* Motor Efficiency
P
Decel
= P
Drive1
+ P
Drive2
+ …
Calculate the input current required on the regenerative unit during
deceleration, taking advantage of the 110% for 1 minute overload rating of
the regenerative unit.
I
Input
= P
Decel
x1000 / (
√ 3 x V
LL
x 1.1),
where P
Decel
is in kW, and V
LL
= RMS line-to-line AC input voltage.
5. Compare the absolute values of the input current required for the
regenerative unit during acceleration, deceleration, and steady state.
6. Select the regenerative unit with the input current rating that meets or
exceeds the worst case input current.
(1) P
Motor
is the motor power required for the application. The P
Motor
could be positive if that section of the machine is motoring, or
negative if that section of the machine is regenerating.