bonitron M3460, Customer Reference Manual

Page: 57 / 68

D_M3460_D_CMAN_vall_00a 4/17/2020
57
The total capacitance of the series string is given by:
C
tot
=
C
eol
n
series
∗ n
parallel
C
tot
=
132F
8
∗ 1 = 16.5F
Now, the total energy that can be delivered to the load is given by:
J
Available
=
1
2
∗ C
tot
∗ (V
Charge
2
− V
CapEnd
2
)
J
Available
=
1
2
∗ 16.5F ∗ (368V
2
− 338V
2
) = 175kJ
The equivalent
𝐸𝑠𝑟
of the string is given by
Esr
tot
=
n
string
∗ Esr
n
parallel
Esr
tot
=
8 ∗ .01Ω
1
= 0.08Ω
The total extraction losses of the string is given by
J
LossTot
= Esr
tot
∗ I
Peak
2
∗ T
out
J
LossTot
= 0.08Ω ∗ 235A
2
∗ 2s = 9kJ
Now the total required energy can be compared.
J
Out
+ J
LossTot
< J
Available
150kJ + 9kJ < 175𝑘𝐽
This combination of capacitors will be adequate for our example application.
If the application required more energy, then capacitors can be added in series,
and the calculations redone as in 7.2.1. If the charge voltage exceeds the
maximum input voltage for the M3460R, then the minimum series string
combination should be used in parallel and the process repeated.
7.3. S
TEERING
D
IODE
S
HARING WITH A
B
ONITRON
M3460 R
IDE
-T
HRU
Diode sharing is used to decrease the cost of implementing M3460 modules to existing
drive systems that are not common bussed. The use of diodes will prevent drive
busses from “back feeding” each other, by allowing energy to pass one way only. This
can be useful to keep the bridge from one drive feeding other drives and becoming
overloaded during normal operations.
For Ride-Thru applications, the energy is allowed to pass from the M3460 to the drives,
but is blocked from the drives to the M3460. Figure 7-1 is a block diagram of a diode
sharing example.