Final Testing; Load Bank Test - Kemppi Master S 400 Service Manual

Service manual Master S 400 and 500

4.4. Final testing

After the machine repair and low voltage tests, it is good practice to carry out some load tests and finish
with some test welds. Only then is it possible to guarantee the machine is working correctly.

4.4.1. Load bank test

CC (MMA and TIG machines) curve's secondary voltage can be calculated when a certain current is set:
 I 
U , 0 04
MMA mode:
2 2
Voltage has to be set for the nominal curve to get the correct output power. E.g. when making a PTC test
the correct values must be used to meet the duty cycle specified in technical specification.
Most useful tests to be made with a load bank are to check maximum and minimum current and panel
display values.
The following example uses 140A so the correct voltage can be calculated using the equation below:

I 140 A
2
  
U I , 0 04 20
2 2
   
140 A , 0 04 20 25
Output voltage should be 25,6V.
Example: MMA mode load bank test, welding current 140A and output voltage 25,6V
Turn the machines main switch OFF
Connect machine to the load bank and check that there is no load added.
Turn the machines main switch ON,
Adjust machine current to desired level (this example uses 140A)
Add some load to get the inverter operate, be fast in switching because arcing may exist
between the connection surfaces of the switch
Measure load voltage by a DMM
Add or decrease load to get the desired voltage
If using active load bank, instead of increasing or decreasing load, it is only necessary to select MMA
nominal curve and then set the test current value on the machine. The Load follows automatically the
current value and the output voltage will be correct.
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Kemppi Oy

20
6 , V
Version 1.1 5.9.2014