Both contact assemblies must make contact to energize both the magnetic and
high voltage coils and capacitor, but must also allow this contact to break when
the vibrating contact is pulled away by the attracting force portion of the
alternately attracting/repelling magnetic field. This action of making and breaking
these two contacts sets up an oscillation in the circuitry, generating the high
voltage at a high frequency (of 500 kHz).
If the gap between the contacts is too large, no contact will be made, the circuits
will not be connected; the unit will not generate the high voltage. If the adjusting
shaft is turned clockwise too much, both contacts will be pressed together
towards the magnetic coil, but the spring tension on the vibrating contact will be
too great for the attracting magnetic field to overcome. Hence, the contacts will
not break contact, and the unit will not produce the high voltage.
Once the contact gap is adjusted properly to make and break the connection
between contacts, the distance can be adjusted, to a limited range, to vary the
output of the voltage, the greater the gap the lower the voltage, and vice versa.
However, the gap distance is also affected by the pull of gravity of the metal plug
of the vibrating contact, especially at the lowest output level. If, for example, if
the unit is adjusted to resonate while the unit is held horizontally, if then
positioned to point downward, the gap distance will increase, breaking the
connection between contacts. If the unit is then held vertically upward, the gap
distance decreases, making the connection again between the contacts.
For example, if the Model BD-10A/AS was set for an output voltage near the low
range of operation, at the horizontal position, it might have an output of 23 kV,
but be intermittent, cutting out on occasion, if held with the switch pointing down,
and continuous if the switch was held upright. When held pointing down, the unit
might no longer generate an output. When held pointing up, the unit might
generate a voltage of 27 kV, with a continuous output.
Normally, units should be adjusted to function in the orientation in which it is
used, or adjusted to operate at the higher output level, where the orientation
issue is not as much a problem.
Alternately, the Model BD-50E is recommended. The vibration contacts are
inside a power control unit, and are always horizontal when the power control
unit is placed on a horizontal surface. The high voltage coil is held in the black-
plastic housing. It can be held in any position without affecting the position of the
contact gap. In fact the contact gap is factory set for optimal performance, and
the output is changed by a 9-step switch, with positions marked on the power
control unit front panel. This also makes the calibration of this unit more positive,
and repeatable, then the Model BD-10A/AS.
For voltage ranges below 20 kV, another option is the Model BD-40E. It uses
solid-state circuitry, instead of vibrating contacts to adjust the voltage and set up
the circuit oscillation, producing the high voltage, 2 kV to 20 kV, at 500 kHz.
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