Parker Hannifin 88-021610-01G - Manual (Page 178)

Parker Hannifin
178 Aries User Guide
mgh E
p
=
Where
E
p
= potential energy (Joules)
m = mass of forcer and load (kg)
g = gravitational constant (9.81 m/s 2 )
h = vertical height change during deceleration (m)
Energy Absorbed by Drive Capacitors
The Aries drive’s capacitors can store energy. With motor deceleration, the
drive capacitors absorb some of the kinetic and potential energy. While the
capacitors absorb energy, the bus voltage increases. Later, the capacitors
release that potential energy in subsequent accelerations, or into typical drive
losses.
If too much energy is absorbed by the capacitors, the Aries drive faults from
over-voltage. Under these circumstances, an external power dump resistor is
required.
That ability to absorb energy can be defined in terms of capacitance and
voltage.
) (
2
1
2 2
NOM TRIP C
V V C E
− =
Where
E
C
= energy that can be absorbed by the drive capacitors (Joules)
C = drive capacitance (Farads)
V
TRIP
= power dump trip DC voltage (400 VDC for Aries drives)
V
NOM
= nominal DC motor voltage (typically AC mains voltage at
2
; for
example, 120 VAC *
2
= 170 VDC)
Fortunately, for a given drive the capacitance and voltages are fixed. Table
58 provides the needed information and results from the above calculation.