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Generator Power and Lathe

Discussion in 'Woodturning Discussion Forum' started by Ed Weingarden, Aug 5, 2020.

  1. Ed Weingarden

    Ed Weingarden

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    Mar 17, 2006
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    Location (City & State):
    Canton, Connecticut
    I'm one of the 50% of CT residents without power, and currently (no pun) running the house with a portable generator. I don't run too much in the way of power consumption (fridge, freezer, computer and TV mostly). Just wondering if there is any risk to the motor on my Grizzly G0800 by using power from the generator. The motor is 220V/10A/3hp, so I think the wattage draw would be about 2200W. The generator puts out 7000W. I just don't know if there is something different about the power from the generator vs that from the utility lines, which could adversely affect the motor. Any electrical engineers out there? Thanks.
     
  2. Brandon Sloan

    Brandon Sloan

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    Mar 7, 2019
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    Location (City & State):
    Victoria, Texas
    No difference in power. As long as the generator isn’t overloaded, everything will work fine. The generator has a breaker for protection as well. I’ve seen lathes run on generators without any issues.
     
  3. Richard Coers

    Richard Coers

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    Location (City & State):
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    No trouble with the motor but I would be concerned about the VFD. How clean of power do you get with your generator? Is it an inverter generator? I wouldn't run my machines on a cheap traditional generator, but I'm cautious that way.
     
    Tim Connell likes this.
  4. Joe Kaufman

    Joe Kaufman

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    Apr 18, 2009
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    54
    Ed, you could raise the question with the manufacturer of the lathe inverter. I agree that the motor shouldn't be a problem. My brother has lived with a 5 or 10KW generator for 60 years. 2 houses, 2 refrigerators, 2 chest freezers and a 3/4 hp pressure pump. Depending on the load, the pressure pump could drag the line voltage below 90 volts while it cycled on. Early TV's were the only appliance that tended to have a shorter life.
     
  5. Bob Mezzatesta

    Bob Mezzatesta

    Joined:
    Sep 13, 2014
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    Location (City & State):
    Ontario, Canada
    Lots of power outages here. We have a generator for the house and shop and one for the stable. Wouldn’t consider running either of my lathes because of VFDs. I even turn off the wifi router and wireless receiver. Generator power is too spiky for some electronics. Motors no problem.
     
    Tim Connell and charlie knighton like this.
  6. Roger Chandler

    Roger Chandler

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    Nov 26, 2009
    Messages:
    678
    The sine wave is incorrect for the VFD with a portable generator. I explored this back a few years ago, and I also have the G0800 & two other lathes. Not worth risking an electronic issue that fries the VFD. This info was passed on to me by an electrical engineer. Maybe Bill will chime in with some info.
     
  7. Dennis J Gooding

    Dennis J Gooding

    Joined:
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    Location (City & State):
    Grants Pass Oregon
    I am an electrical engineer and while I have not looked at the waveform of my emergency generator output, I can't see any reason why there should be any spikeiness. The generator is a classical AC device with a rotating magnetic field interacting with coils of wire and should produce an essentially perfect sinewave output. Spikeiness is usually is associated with waveform choppers used in voltage converters or VFD devices.
     
    Brandon Sloan likes this.
  8. Ed Weingarden

    Ed Weingarden

    Joined:
    Mar 17, 2006
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    Location (City & State):
    Canton, Connecticut
    Thanks for all the feedback. Based upon a couple of the replies, I decided to wait it out, and not risk doing damage to the VFD. The power was estimated to be out for 7 - 10 days. Before I turned the generator on this morning, I threw the main breaker and to my surprise, I'm back on line. At some point, I'll see if I can get more info from the manufacturer of the VFD.
     
    Mark Jundanian likes this.
  9. Dennis J Gooding

    Dennis J Gooding

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    I am referring here to motor-generator emergency power systems. Units based on using an inverter to produce AC power from batteries or solar sources are a different story. Maybe some respondents are not making that distinction.
     
    Brandon Sloan likes this.
  10. Ron Solfest

    Ron Solfest

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    All generators are not created equally. I would have no concern running my Powermatic (with VFD controller) on an inverter-generator which puts out a true sine wave, and I’ve run various electronics successfully on. These are higher cost generators, typically with sound insulation etc.

    I would not risk running sensitive electronics (including VFD controller) on a contractor style generator. These are cheaper, usually open frame, where the engine runs at constant rpm regardless of the load. Output of these are not as clean as inverter-generators.
     
  11. Roger Wiegand

    Roger Wiegand

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    OK, I'm confused, doesn't a generator need to run at constant rpm to produce power at a constant 60hz? Obviously I'm not an electrical engineer! Is there electronic wizardry that adjusts the frequency coming out of generators? It seems like in old (steam powered) generators I'm more familiar with the designers went to a lot of trouble to be able to hold speed constant while delivering more or less power to the generator.

    Given the declining state of our power grid and advancing age and dependence on electrically powered devices we recently installed a whole house Generac 15 kVA system. The guys who sold it to us assured me that it was fine to use all of our electronic devices while running on the generator; indeed we've had two outages in the three weeks since it was installed and everything kept running just fine. Is what they told me not true, and are we courting disaster?


     
    Mark Jundanian likes this.
  12. Dennis J Gooding

    Dennis J Gooding

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    Roger, like you, I have a whole-house generator, propane-powered in my case. For this application, it is considered important to maintain a frequency very close to 60 Hertz so that clocks and timers do not drift much during outages. The frequency for any given unit, is determined by engine speed which is controlled by a sensitive governor system. In the case of a two-pole generator, like mine, the engine speed is maintained at 3600 RPM, regardless of load up to the maximum capacity of the generator. (A four-pole generator would run at 1800 RPM.) I have no data on contractor portable motor generators, but I would expect that accurate speed regulation is not considered important. However, even with these, I would not expect to find voltage spikes.
     
  13. Ron Solfest

    Ron Solfest

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    I can’t speak for power quality on whole- house generators, but would assume they’re good.

    The OP asked about a portable generator. The standard contractor grade portable runs at constant speed, but when loaded down it will vary enough that the wave output differs significantly from a pure sine wave. Those are the ones I would not use with sensitive electronics.

    Portable inverter-generators actually convert the generated AC voltage to DC and then back to 60Hz AC so they produce a much higher quality sine wave output, typically spec’d at 1-3% of perfect sine wave I believe. These are the portable generators play well with sensitive electronics.
     
  14. Tom De Winter

    Tom De Winter

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    The inverter-generators do not depend on RPM to regulate the output frequency.
     
  15. Don Wattenhofer

    Don Wattenhofer

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    The VFD has a rectifier on the single phase input and it then constructs a 3 phase sine wave at the voltage and frequency requested example 50% speed would require an out put voltage of 120 V 30 Hz 3 phase. The VFD uses pulse width modulation, which is rapid on off switching to approximate that sine wave, therefore the VFD usually protects it self due to the DC bus, as it sends electrical noise back on the line.
     
    Brandon Sloan likes this.

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