testing generator hertz

[Gary - K7GLD]

Originally Posted by Gary - K7GLD

On a typical Onan type alternator genset, the ratings for frequency are usually spec'd at the nominal voltage output - about 120 volts. Fact is, the voltage itself has to be pretty far off to the high/low side before the voltage frequency changes appreciably - in fact, the VOLTAGE delivered will probably be a critical issue LONG before the frequency is!

Folks often get unnecessarily paranoid about power frequency, because MOST electrical/electronic devices will continue to operate satisfactorily with rather significant deviations from the 60 cps range...

I was interrupted as I was typing the above, and neglected to include that the type genset I was referring to, typical alternator type - usually reaches both the rated output voltage AND frequency at a pretty specific motor RPM - and that the voltage/RPM shift will usually become an issue well before the frequency does...

[CJ7ole]

I have a digital Amprobe clamp-on style meter which will measure not only amperage but voltage, ohms, FREQUENCY, as well as a few other things, Under $70 for a professional level meter. I checked the frequency of the power in my home and it read 60.0 hertz. AC Clamp-On Meters by AMPROBE - Clamp-On Meters by Zoro Tools Industrial Supplies
They come with probe wires.

[jauguston]

Pretty hard to beat the Kill-A-Watt. For non-inverter generators cycles and voltage is controlled by engine rpm. With no or minimal load the engine rpm should be adjusted to show 62 cycles. The engine governors are not really precise at holding constant rpm. When loaded to near full load cycles will likely drop to about 58.That range is fine. If you get erratic readings the first thing to try is lubing the throttle linkage and look for sloppy loose joints.

Jim

[Koop]

The generators I'm familiar with rely on the rpm of the generator motor to set the frequency of the output wave (i.e. 3600rpm equals 60 cycles per second). I use my Fluke muli-meter to check the generator I have for my home. If the govenor on the engine holds a steady 3600 rpm, I have 60 hertz.

[Genset]

Good subject, First off, beaware the for electrical equipment to earn the UL sticker, it must meet two standards as for generators,
+/- 10% on Voltage, meaning 108-132 Volt, Me I perfer 115-125 Volts
+/- 5% on Frequency, meaning 57-63 Hertz
UL rated equipment is supposed to operate properly n the above conditions.
This is what we were taught at the Onan Factory Schools back in the mid 70's, and I guess it has not changed as I have never heard any thing different since.
Also most Onan air cooled gensets do not like voltage above 127 Volts.
FWIW
Dave

[mmartinkus]

The frequency is determined by generator speed. To produce 60 CPS the generator must run at either 1800 or 3600 RPM.

[TLGPE]

Almost true; some are belt driven and use a different ratio. My Generac seems to have about a 3/4 ratio timing belt drive. Runs at about 2400 RPM.

Just a note to be contrary....... :-)

Tom