Tweco 6000GST Merlin Plasma Cutting CE Slave Power Supply - Manual (Page 33)

Manual 0-2653 3-15 INSTALLATION PROCEDURES
Approach From Front Or Rear
Do Not Lift From Sides
A-01499
Figure 3-20 Lifting the Power Supply
3.15 Pilot Resistor Adjustment
This Sub-Section applies only to the following Master and Slave
Power Supplies:
• All Merlin 6000GST Master Power Supplies
• Slave Power Supplies with the revision letter 'E' or later
on the data tag
• Slave Power Supplies that have been retrofitted with Pi-
lot Resistors
Master and Slave Power Supplies, as noted above, contain
adjustable pilot resistor circuits. For output current below 250A,
only the pilot circuit in the Master Power Supply is activated.
For output current above 250A the Master and Slave Power
Supply pilot circuits are activated.
Master and Slave Power Supply pilot resistors are initially set
at the factory and may need to be adjusted to the customer's
input power (see Notes).
NOTES
The instructions in this Sub-Section apply to the
Master Power Supply only.
To adjust the Slave Power Supply pilot resistor,
refer to the Manual supplied with the Slave Power
Supply.
WARNING
Disconnect primary power at the source before
assembling or disassembling power supply, torch
parts, or torch and leads assemblies.
The pilot current consists of two parts:
1) Minimum or “background” level
2) Pulse or peak level
The background level has to be high enough that the pi-
lot will not sputter or go out, but not too high to cause
excessive wear of the torch consumables. Adding pulses
of current on top of the background current allows greater
arc transfer distance without increasing the torch part
wear. The amount of pilot current is determined by the
value of the pilot resistors and the open circuit voltage
which varies with the input line voltage. Both the Mas-
ter and the Slave Power Supplies should be adjusted the
same. Wire #99 tap sets the background level and wire
#150 tap sets the pulse level. To set the pilot background
and pulse levels use the following procedure:
1. Remove the left and right side panels of the Mas-
ter Power Supply.
2. Locate and identify the pilot resistors (R16, R21 and
R22) which are on a bracket in front of the fan.