Bird Technologies 6730B Series - Manual (Page 14)

CAUTION
Model 6735-300A is rated for 1200 W operation for a
maximum of ½ hour only. For continuous operation, the
maximum wattage should be restricted to 1000 W. It is
recommended that if frequent use above
1000 W is contemplated, the instrument be equipped
with the thermoswitch assembly.
As an optional item, the Model 6735-300A load portion
can be provided with a thermoswitch assembly, P/N
2450-056. When installed in the radiator, it will prevent
possible damage occurring from accidental transmitter
power overload or equipment malfunction. Being normally
closed, the thermoswitch opens at a maximum safe tem-
perature of +155°C (+311°F). Connected in series with the
transmitter interlock, it cuts off transmitter power if the
load coolant temperature exceeds this value. The assem-
bly consists of thermoswitch body, P/N 2450-040, with
coupling jack, P/N 2450-018, attached.
Cooling The dielectric coolant is chosen for its desirable dielectric
and thermal characteristics. Cooling of the load is accom-
plished by natural fluid and air convection currents. The
dielectric coolant carries the electrically generated heat
from the resistor to the walls of the cylindrical cooling
tank. This tank is encased in a set of radiating fins con-
structed from heavy gauge aluminum alloy and firmly
pressed onto the cylinder. The heat from the dielectric oil
is transferred to the surrounding air by the fins. The
Model 6732B uses 0.35 gallon (1.3 liter) of coolant, the
Model 6734B030 uses 0.9 gallon (3.4 liter), the Model
6735-300A uses 2.9 gallons (11 liter), the Model
6736/A/-030A uses 1.1 gallons (4.2 liter), and the Model
6737/A/-030A uses 0.9 gallon (3.4 liter) of coolant.
Expansion of the coolant, caused by the rise in its tem-
perature, is allowed for by means of a synthetic rubber
diaphragm (not visible) in the rear cover dome of the load
for the Models 6732B, 6734B, 6734B030, 6737A and
6737-030A. In addition, the Models 6737A and 6737-030A
are equipped with a cooling coil for circulating water that
will remove most of the generated heat from the dielectric
coolant. Models 6735-300A, 6737A and 6736-030A have a
spring loaded vent plug rather than a diaphragm for re-
lieving the excess pressure caused by the coolant expan-
sion.
Bird Model 6730B Series Termaline Wattmeter
6