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The fear of
thermal shock (heat shock), caused by the instantaneous
application of full voltage and current, has been addressed by ramping
up the current from 1 amp to the maximum. This is especially important
in an application having fine wire gauges because it prevents the coil
from acting like a fuse. A 10% increase in current results in 21%
increase in power dissipated through the coil as heat. Another benefit
of ramping is the increased longevity of the switching components.
 The over-heat
protection feature shuts down the supply if the part is
not bonded within a specific time period or when the temperature
set-point is exceeded.
If the coil does not reach the specified
temperature or resistance cutoff before the failsafe time expires,
the bond sequence will be terminated. Temperature sensing can be
set to either ambient or real-time. (temperature is retrieved from
an infrared sensor aimed directly at the coil). The bonding power
cutoff control can be set to either the resistance or temperature
mode.
Dwell
time allows you to maintain a given temperature for a
specific amount of time on the coil after it has reached the
bonding temperature/resistance set-point. This temperature
set-point is programmable and generates equal temperature
distribution to all coils. The feature is especially important in
odd bar armature applications since one side of the armature will
dissipate more power than the other side. For example, one side
(3-coils) of a 7-bar armature will dissipate 33% more power than
the other side (4-coils).
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