M3534R 40&85A
46
the maximum input voltage for the M3534R, then the minimum series string
combination should be used in parallel and the process repeated.
7.5. D
IODE
S
HARING WITH A
B
ONITRON
M3534
R
IDE
-T
HRU
Diode sharing is used to decrease the cost of implementing M3534 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.
For Ride-Thru applications, the energy is allowed to pass from the M3534 to the drives,
but is blocked from the drives to the M3534. Figure 7-1 is a block diagram of a diode
sharing example.
Below are some basic guidelines for using diodes in this manner for M3534
applications.
1.
Drives should have equivalent DC bus levels as would be found on equal size
drives of a common manufacturer.
2.
Drives should be on same AC feed and grounding. There must be no isolation
transformers between the drives and or M3534 modules. Different feeds may
have different potentials and may cause circulating currents or ground faults.
3.
If line chokes or harmonic filters are used, all the drives should be connected to
the output of a single choke or filter. Individual input harmonic filters or line
chokes can cause unequal potentials with respect to earth.
4.
The 3534 connection should be downstream of any input line filter. Input line
filters cause lower DC bus levels. If a M3534 is placed upstream, the Ride-Thru
DC bus can be higher than the drive bus, and current can flow through the
M3534. This can cause constant activity and overheating. It may be necessary
to lower the threshold for these applications.
5.
Ground Fault sensing should be done upstream at common point of line
connection, upstream of line filter, if used.
