Fimer x204 gives -39 Volt Output Voltage when props connect to outputs reverse; but when it is straight it gives the correct output value of 55 V

[PhysicsEngineer]

Fimer x204 IGBT inverter arc welding machine gives -39 Volt Output Voltage when multimeter props connected to the outputs reverse; but when it is straight it gives the correct output value of 55 Volts

How to fix it if it's a bug? What should be checked and measured on the machine and on the electronic card, and possibly which electronic components should be replaced?

When the this same machine is turned on, it sometimes gives a very high output voltage of 85 Volts, after 5 minutes it goes down to 55 Volts. Why???

 

[voipio]

Dodgy multimeter?

 

[PhysicsEngineer]

Dodgy multimeter?

No, I am sure it is not. Any other suggestions?

 

[voipio]

With very little information to go on, it is difficult to offer any help. This, and the related videos, may be useful:

 

[mtt.tr]

What ever way you put your multimeter leads you should get the same result just negative in one way. I assume you are measuring open circuit

 

[eddie49]

The output of an inverter welder may not be true DC - i.e. a steady uni-directional voltage. In this thread:

MIG welder torch voltage - general question

I've been using my Uptime160 MIG for a while now and it's working fine (slightly erratic welds recently but solved with a new tip). After reading threads about voltage, amps and wire speed I decided to test the welder to see what the controls actually control and what the voltage is at the tip...

www.mig-welding.co.uk

an oscilloscope showed a very spiky pulse-width modulated (PWM) output.
It's possible that your digital voltmeter interprets these spikes as a different DC voltage depending on polarity. I would suggest comparing the DVM readings with a traditional moving-coil ( analogue ) voltmeter.
As mtt.tr suggested, open-circuit voltage readings on inverter welders vary greatly, better to use a "Load Bank" to check the on-load voltage:

TEC ARC CALIBRATOR 500i WELDING, LOAD BANK, CALIBRATION | eBay

TEC ARC CALIBRATOR 500i WELDING, LOAD BANK, CALIBRATION. USED ONLY A FEW TIMES, GREAT CONDITION, ALL FUNCTIONS WORK, CABLES AND WIRE FEEDER EURO CONNECTOR INCLUDED.

www.ebay.co.uk

For a cheaper alternative, Google "hillbilly load bank".

 

[PhysicsEngineer]

The output of an inverter welder may not be true DC - i.e. a steady uni-directional voltage. In this thread:

MIG welder torch voltage - general question

I've been using my Uptime160 MIG for a while now and it's working fine (slightly erratic welds recently but solved with a new tip). After reading threads about voltage, amps and wire speed I decided to test the welder to see what the controls actually control and what the voltage is at the tip...

www.mig-welding.co.uk

an oscilloscope showed a very spiky pulse-width modulated (PWM) output.
It's possible that your digital voltmeter interprets these spikes as a different DC voltage depending on polarity. I would suggest comparing the DVM readings with a traditional moving-coil ( analogue ) voltmeter.
As mtt.tr suggested, open-circuit voltage readings on inverter welders vary greatly, better to use a "Load Bank" to check the on-load voltage:

TEC ARC CALIBRATOR 500i WELDING, LOAD BANK, CALIBRATION | eBay

TEC ARC CALIBRATOR 500i WELDING, LOAD BANK, CALIBRATION. USED ONLY A FEW TIMES, GREAT CONDITION, ALL FUNCTIONS WORK, CABLES AND WIRE FEEDER EURO CONNECTOR INCLUDED.

www.ebay.co.uk

For a cheaper alternative, Google "hillbilly load bank".

can you please be more specific or provide more explainations I did not understand anything...

 

[voipio]

What Eddie49 is saying is that the output of a switched mode/inverter welder is not smooth DC, nor is it simply rectified AC, so the measurements given by a digital multimeter may not accurately reflect the average DC value at the output, and may, indeed, give different results when the test lead polarity is reversed, simply because the multimter input voltage may be being sampled in a way that gives inaccurate results on non-smooth DC signals.

 

[Alan Reynolds]

You may get a more accurate interpretation of the voltage if you use a meter with a needle indicator like an old AVO. This wouldn’t react to the fluctuations or noise on the line.some cheap digital meters give a different voltage, depending on the range you use. I prefer old fashioned meters, got three of them.