We are trying to run an AC generator on an RV for a customer. On an RV as you drive the engine RPM goes up and down. As I understand it, that would change the outlut AC frequency.

Is there an electronic device that I could use to keep the output frequency at a steady 60 Hz?

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    \$\begingroup\$ Look at "inverter generators" \$\endgroup\$
    – user16324
    Jan 8, 2021 at 19:34
  • \$\begingroup\$ You could use a DC motor and AC gen with the field current regulated by a tach. Or x kW motor speed control Reference set to line f for high power , or just an electronic x kW inverter. It all depends on the quality of AC sine or square and W/$ budget \$\endgroup\$ Jan 8, 2021 at 19:38
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    \$\begingroup\$ There is a substantial difference in AC quality , impedance and load regulation error in the designs. So estimate specs 1st \$\endgroup\$ Jan 8, 2021 at 19:44
  • \$\begingroup\$ Another possibility is to only buy appliances that can handle changing frequency. But since you said this is for a customer, I wouldn't recommend it. Way too complicated. \$\endgroup\$
    – user253751
    Jan 8, 2021 at 22:59

1 Answer 1


If the load is a small one, an inverter from 12V is the best way to go. In fact it's the only practical solution for a varying engine RPM source.

For a larger load, you need a separate generator unit with a fixed RPM.

That said, you can still buy 120V alternators that are belt-driven intended for under-hood generation. They were popular some decades ago on utility trucks as an alternative to a separate gasoline generator. Unfortunately they require a fixed RPM from the engine, so they aren't suitable for an RV in motion.

This company sells them: https://www.fabcopower.com/generat/bgen.htm

  • \$\begingroup\$ We are using a 5000 watt inverter now to do what we want We would have to run more like a 12 to 15,000 watt unit. Which is not practical due to the cost of a good quality inverter We would have about 9 to $10,000 invested. I would like to just run a AC generator off of the engine. I would assume somewhere out there is a controller to control the output and keep it at a steady 60Hz no matter what the output is. I know for instance on our large TIG welders at work when we're doing AC welding with aluminum we can change the frequency anything from about 52 120 hz. \$\endgroup\$ Jan 9, 2021 at 1:02
  • \$\begingroup\$ These type of TIG welders also use inverters. They output square waves vs. sine waves used for power inverters. Different animal. \$\endgroup\$ Jan 9, 2021 at 3:09

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