WTC MedWeld 3005, Operator'S Manual

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This section is a brief description of the following components
provided with the MedWeld 3005 control:
• Circuit breaker
• Isolation contactor (optional)
• Control transformer
• Current coil
• Firing card
• Cascade firing board and
• SCR assembly.
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A circuit breaker provides the means to safely disconnect power
from the control in case of a failure. Incoming power enters the
control enclosure through the access plates at the top right of the
cabinet.
The standard single-pack control configuration uses a 250 A. (or
higher) 2-pole circuit breaker. Tri-pack controls use a 400 A. (or
higher) 3-pole breaker.
The supply voltage (380, 480 or 600 VAC) is connected to the
single-pack breaker at terminals L1 and L2. For a three-phase
configuration, it enters at terminals L1, L2 and L3.
If the optional isolation contactor is used, connecting the control
to the weld bus and the circuit breaker in the ON position applies
supply voltage to the contactor’s normally-open contacts. In
single-pack configurations, the contacts are designated 1L1 and
1L2; for tri-pack configurations, they are 1L1, 2L2 and 1L3.
If your control does not use the isolation contactor, voltage from
the circuit breaker is applied directly to the SCR assembly.
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The isolation contactor applies voltage to the SCR assembly. In
case of a catastrophic failure, it also removes voltage from the
primary.
The isolation contactor is driven by a single solid-state relay,
based on the status of the CONTROL STOP and WELD/NO
WELD inputs. Voltage must be present at these two inputs