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  • Generator voltage and Hertz...

    If I change the generator rpm's to maintain proper voltage at 'far end', will that also change the Hertz?

  • #2
    In the case of small or residential generators, you can alter the engine rpm settings by making a few changes on the control panel of your unit. Follow the steps given below to alter your generator frequency from 60 Hz to 50 Hz:

    (a) Run your generator engine and tune the frequency meter on your control panel to read 50 Hz.
    (b) Check the AC voltmeter or potentiometer as the case may be and read the voltage output of the generator. The output voltage decreases as you reduce the frequency and may be lower than the desired value.
    (c) Adjust the AC voltmeter or potentiometer on your control panel till you obtain the desired output voltage at 50 Hz.
    (d) By making similar modifications on the control panel, you can increase the frequency from 50 Hz to 60 Hz.
    (e) If the control panel does not display the frequency, you will need to first connect a device that will measure the frequency while the generator is in operation and then change the engine rpm.
    (1) Changing Engine Speed to Vary Output Frequency
    Present-day generators consist of an engine directly connected to an alternator to produce electricity. One of the most common ways of changing the output frequency of a generator is to change the rotation speed of the engine.

    The two factors are related as per the following formula –
    Generator Frequency (f) = Number of revolutions per minute of the engine (N) * Number of magnetic poles (P) / 120
    Conversely, P = 120*f/N

    As per the above formulae, a 2-pole generator producing an output frequency of 60 Hz has an engine speed of 3,600 rpm. To change the output frequency to 60 Hz for the same generator configuration, the engine speed needs to be reduced to 3,000 rpm. Similarly, for a 4-pole generator, an engine speed of 1,800 rpm produces output of 60 Hz. Reducing the engine speed to 1,500 rpm yields an output of 50 Hz.
    Last edited by HayZee518; 05-29-2011, 03:29 AM. Reason: added info

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    • #3
      Volts and Freq. ....

      I was afraid of that. My generator is hooked up on a line about a hundred feet from the panel. To get the proper voltage at the panel I raised the engine rpm's until the meter read 120 at the panel. But that increases the Hertz as well. So what's the fix, besides bringing the generator closer? This gen does not have any control panel displays. It's only a Coleman 6500.
      By the way, I have used it in this configuration several times. Refrigerator, 220v well pump, a couple lights and a tv.
      Last edited by mrcaptainbob; 05-29-2011, 10:25 PM.

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      • #4
        Originally posted by mrcaptainbob View Post
        I was afraid of that. My generator is hooked up on a line about a hundred feet from the panel. To get the proper voltage at the panel I raised the engine rpm's until the meter read 120 at the panel. But that increases the Hertz as well. So what's the fix, besides bringing the generator closer? This gen does not have any control panel displays. It's only a Coleman 6500.
        By the way, I have used it in this configuration several times. Refrigerator, 220v well pump, a couple lights and a tv.
        Get a larger cable so you don't get the voltage drop. Paul

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