UG:014
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Page 13
Paralleling
The paralleling and current sharing capability of the devices can be demonstrated by
stacking multiple evaluation boards and interconnecting the inputs and outputs with
standoffs of sufficient current rating to create a parallel array. When paralleling VTMs,
in standalone VTM® operation, VC pins should be connected together to enable the
synchronized startup.
PRM® boards can also be connected in parallel to create high power PRM-VTM arrays.
PRM input, outputs and interconnect signals need to be connected in parallel using
same size standoffs. Each VTM requires a VC signal from a PRM in order to start and it is
recommended to connect one PRM VC to one VTM VC using the connector J13 on PRM
board and J14 on VTM board when possible. If needed a single PRM VC can be used to
drive up to two VTMs (will require additional off board connections).
Push Pin Heat Sink Installation
Each VTM demonstration board comes with its own heat sink and push pins for
installation. Before testing, it is highly recommended that the heat sink be installed in
the appropriate location for each board. When installing the push pin heat sink, use
caution not to exceed the maximum compression on the device listed in the data sheet.
For most lab environments a fan blowing across the evaluation board is recommended.
Using the VTM Evaluation Board for Reverse Operation
VTMs are capable of bidirectional power transfer between the Primary and
Secondary power terminals. Certain VTMs such as the VTM48EF040T050B0R, and
VTM48EF120T025A0R are qualified for continuous operation in reverse (power transfer
from Secondary to Primary).
Reversible VTMs are usually designated with an R as the last character of the part
number, however, refer to the datasheet to determine if a particular VTM is qualified for
continuous reverse operation.
Reverse operation with a PRM-VTM configuration is beyond the scope of this document.
In standalone operation, the applied VC voltage must be referenced to -PRI(-IN). VC
can be applied before or after the secondary (source) voltage. Applying VC after the
secondary voltage will result in a non-negligible amount secondary inrush current as
described in the datasheet. Refer to the datasheet for the peak secondary inrush value
and ensure the source is rated appropriately. Fusing for the evaluation board is located
on the primary side. If fusing on the secondary (source) side is required, then it should
be added externally based on the device ratings.
In order to test a qualified VTM in the reverse direction, follow the the procedure for
VTM standalone operation and make the following changes:
1.
Connect the voltage source to the Secondary (Output) lugs.
2.
Connect the load to the Primary (Input) lugs.
Ensure the applied source voltage has the correct polarity and is within the Secondary
Voltage ratings of the VTM. It may be necessary to install an input capacitor across the
Secondary terminals to decouple the input source.
