How does a generator put the prober hertz on a line? I have a generator/welder that I cAnt seem to get the volts/hertz lined up to work properly thanx


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The frequency of the alternator is just dependent upon speed and the number of poles the alternator is design with. The formula is:

freq [Hz] = Speed [RPM] X poles / 120

So, for a 2 pole alternator the engine would need to run at 3600 RPM to provide 60 Hz. A 4 pole alternator should run at 1800 RPM for 60 Hz, and a

6 pole alternator at 1200 RPM. Note that poles always come in pairs.

Bottom line, the generator's engine should be running at or close to one of these design speeds to deliver the proper frequency. A tolerance of 5% or so is usually allowed for frequency on most electrical equipment.

As far as voltage goes, it is a function of the speed and the alternator's field current - assuming the alternator has a wound field. As the generator's engine should be running at a fixed speed, the output voltage can only be adjusted by changing the alternator field current. The generator should have a built in voltage regulator for this. Most electrical equipment can handle a 10% voltage tolerance.

There are some smaller generators that use a permanent magnet alternator. On these, the output voltage is just dependent on the RPM. Although the load will also drag the voltage down. These tend to have a high output voltage at or near no load. Perhaps 160 to 170 volts RMS at no load. When fully loaded, the voltage will drop down close to 120 volts RMS. Some sensitive electrical equipment many not like this, but things like light bulbs and electric heaters will usually be ok.

Hope this helps, Big John


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Big John

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