MK Products MK 2000A - Manual (Page 11)

MK 2000A - Owner's Manual - Page 11
The combination may be used to create a wide range of welding
characteristics. For example, when welding thick aluminum sections, CC
operation is often desired due to the increased penetration. In this instance
the Background Level is set to the desired operating voltage (e.g. 20 volts)
and the Background Slope set to a typical CV slope of 4 volts per 100
amperes (19% on dial); the welding condition will be standard CV. To limit
the current increase during the short circuit transfer interval, the Pulse Level
may be set to the desired maximum current (e.g. 240 amps) with a Pulse
Slope of 32 volts per 100 amps (66% on dial) or typically CC.
Another application of the Pulse Level Control is Pulsed Welding Operation.
Conventional pulsed supplies provide increased voltage during the pulse
interval, resulting in a current peak. Since the operating mode is that of
constant voltage, the actual current peak depends very critically on the load
impedance (wire feed rate and tip-to-work distance).
Using the Pulse Level Control with the Pulse Slope set for Constant Current
operation, the pulses on the pulse height may be set to 100%, permitting the
power supply to go to maximum output voltage. The pulse current is then
controlled by the Pulse Level, which is set to the desired peak current. Under
these conditions, the welding condition during the pulse is constant current,
and largely independent of wire feed rate and tip-to-work distance.
The MK2000A has built in protective circuitry to protect it from excessively
high or low input voltage and from any load condition. Under overload
conditions, the unit will automatically shut down and reset when conditions
are normal.
The physical layout logically separates input, switching, output and control
functions for ease of fault isolation and sub-assembly replacement. All
components are very conservatively rated and reliability is exceptional.
Mechanical
Careful attention has been given to the mechanical and thermal design of the
power supply. Recognizing the difficult environment in which such equipment
must operate, the MK2000A utilizes a heat exchanger design to eliminate
dust and dirt from the electronic components.
Although the circuit design is exceptionally efficient, it is necessary to remove
heat from the high current devices. This is accomplished by mounting the
input and output rectifiers, switching transistors, main transformer and output
inductor on finned aluminum heat sinks which conduct the heat directly out
of the enclosure and into the air stream from a rear mounted cooling fan.
Outside air is not passed through the electronic enclosure.
All components are securely mounted to insure circuit integrity in spite of the
inevitable rough handling.
The compact size and light weight of this ten kilowatt power supply makes
handling much easier - never requiring hoists or fork lifts to position the unit.
Section 5 MK2000A CONTROL PANEL **
Background Level: Relates to the background level. This is background
voltage for a slope setting of ‘O‘ (CV) and background current for a slope
setting of 100 (CC).
Pulse Level: Also relates to the background level and slope. It is normally set
to establish a limiting value of current (slope near 100) when in short circuit
transfer mode or in pulse mode.
Pulse Width: This control may be set to make the actual pulse length 0% to
100% of the pulse interval.