By following these guidelines, the operator will minimize the risk of damaging voltage spikes and help the welding machine to perform to its full capacity.
Determining the exact generator size required to safely run a welding machine is not always a straightforward process. Some of the factors to be considered are the current draw ratings of the welder, the rated output of the generator and whether this is a genuine rating (unfortunately some generators are over-rated), whether the generator will or will not be used to run other power equipment at the same time, etc.
For recommended generator sizes to run specific machines, refer to the instruction manual.
Following is a Suggested minimum generator size ‘rule of thumb’ guide*;
|Up to 160A||7kva||8+kva|
*Note that if it is intended that the generator will be used to run additional equipment at the same time as the welder, the size of the generator should be increased accordingly. These figures are an approximate guide only and should not replace manufacturers recommendations.
** ‘Minimum’ size is the smallest that we suggest to minimize risk if voltage spikes etc, however it may not be enough to achieve full output from the welder.
*** ‘Ideal’ size will further minimize risk of power supply issues and will allow a higher output from the welder.
As we have already mentioned, a good quality generator suitable for running an inverter should have a low THD (Total Harmonic Distortion) output. All reputable suppliers or manufacturers of portable generators will be able to specify what the THD ratings are on their product.
Generators with a low THD rating (6% or less) will have ‘relatively’ clean power and will thus be suitable for running inverter welders.
A generator with a high THD rating (more than 6%) is likely to be a low-quality unit and should not be used to run inverter welders.
The Do’s and Don’ts of using generators with inverter welders:
Suggested Guide for cable size of extension leads used with Inverter Welding Machines*:
|Power Supply||Suggested Minimum
|Up to 200A||240V 10A/15A|| Lengths up to 10m: 2.0mm2
Lengths over 10m: 2.5mm2
*These figures are an approximate guide only and should not replace manufacturers recommendations.
Can I use a small(er) generator to run my welder?
As shown in the table 5a above, the recommended minimum generator size is not less than 7kva (for up to 160A welders). We often get asked questions like “why can’t I use my 5kva generator to run this welder?”.
We also sometimes see other welding machine suppliers suggesting that their machines can be powered by generators as small as 4-5 kva.
Sure the welder might actually operate to some level, but here’s why using smaller under-sized generators is NOT a good idea;
Although a larger generator will cost more initially, a correctly sized (or over-sized) generator will allow you to get the job done right the first time… and greatly reduce the risk of costly damage to your welder. And who ever regrets having ‘too much’ performance?
Here’s another way to look at it; let’s say you’re buying a motor vehicle to tow a trailer. Would you purchase a vehicle that only just has enough power, and must constantly operate close to “red line” rpm to do the job? Probably not! In the same way, buying a generator that has more power/output than what you actually need makes a lot of sense.