Vicor VI-J00 Family DC-DC Converters and Configurable Power Supplies - Manual (Page 43)

Design Guide & Applications Manual
For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies
VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com
Page 42 of 98
Apps. Eng. 800 927.9474 800 735.6200
13. AC Input Harmonic Attenuator Module (HAM)
HAM DO’S AND DON’TS
The following cautions should be observed before applying
power to the HAM.
• It is important that the output of the HAM not be
loaded until the input voltage has exceeded 85 Vac and
the output has begun to boost to 260 Vdc. This means
that if the load on the HAM is a Vicor converter, the
ENABLE Output of the HAM must be connected to the
GATE IN of all Driver modules. The HAM will then disable
the module output until the input exceeds 85 Vac and
the output has been boosted to 260 Vdc. If an external
load is connected directly to the output of the HAM, do
not apply the load until the output of the HAM is
stabilized in boost mode.
• Although the efficiency of the HAM is quite high, it still
dissipates significantly more power than a VI-26x
DC-DC converter. Care should be taken to cool it. Do
not rely on the internal overtemperature shut down to
take the place of adequate planning relative to the
cooling of the HAM. Thermal compound should be
used between the heat sink and baseplate of the HAM,
HAMD and BAMD.
• Power factor is 0.997 at 120 Vac and 0.995 at 240 Vac.
Harmonic content at 240 Vac is therefore somewhat
higher than at 120 Vac. Remember that harmonic
content measured cannot be any lower than the
harmonic content of the AC mains. A precision AC
source is required for accurate power factor measurements.
• The input voltage range of the HAM is 85 – 264 Vac;
however it may not start boosting until the AC mains
has exceeded 87 Vac. Once the HAM has started, it will
operate down to 85 Vac. The HAM contains 2.5 – 6 V
of input hysteresis, therefore if the AC line impedance is
high, i.e., when using a variable autotransformer, the
HAM may start, but the AC line may then fall enough
to drop below undervoltage lockout. When this
happens the AC line will go up, the HAM starts and the
cycle repeats. Therefore avoid soft AC lines at or near
low line.