Frequency Converter

Discussion in 'The Projects Forum' started by Dynamic_Thom, Jul 16, 2015.

  1. Dynamic_Thom

    Thread Starter New Member

    Jul 16, 2015
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    0
    Hello All,

    I want to feed a 460V AC 3Ph 60Hz motor with 45 Hz AC instead of 60 Hz. I could buy a VFD, but thats not really necessary because I don't need to change to many differenc frequencies I just need to operate it at 45 Hz.

    Thanks,
    Static_E
     
  2. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    Some of the people here are very good at what you WANT. (I expect one to answer soon.) Is it really what you NEED?
    Sorry to disparage your intellect but it is customary for people to ask for what they want when there are much easier ways. Personally, I doubt a retail product that only does one frequency. Is it possible you might elaborate or are you sure that's what you need?
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,797
    1,103
    Are you aware of the consequences of changing the frequency? I suggest you have a read of this article.
     
  4. Dynamic_Thom

    Thread Starter New Member

    Jul 16, 2015
    7
    0
    To clarify what I really need is to slow my one speed motor a little bit to satisfy my customer. We figured we could do this by cutting the frequency and I need to figure out the best way to do this.

    #12,
    Thanks for the reply. What I need is what my boss wants, and he wants options. He doesnt want to pay for a VFD that has many more options and features then we need if we can find a cheaper retail product or do it ourselves.

    Alec_t,
    Thanks for you too. The goal is to slow the motor down because it operates our device too quickly. Saturation is definitely something that needs to be considered and I appreciate your help.
     
  5. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,034
    1,653
    Well given you need to run at 3/4 normal speed is there any reason you cant switch out your motor to one with a lower running RPM or change your gearing ratios?


    As for running a 460 VAC motor at a lower frequency you are not going to find many choices for fixed frequency drives being to make a fixed frequency or a variable one is now largely a matter of the programming. Parts cost is not really a issue.

    If cost is such an issue I suggest buying a good used VFD and be done with it. I guarantee you can't design and build a fixed frequency one for less than you are going to be able to buy a good used one.
     
    #12 likes this.
  6. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    There are two types of converters, rotary type and inverter type. Neither are cheap. The rotary type used a motor and A/C generator, driven at the speed to give the desired output frequency. The inverter type used solid-state electronics to first convert your line voltage to DC, and then an inverter configuration to re-convert the power to AC at the desired frequency. 45 Hz is such an odd frequency for working power, thus it would be difficult to find an inverter type that runs at the frequency. You might get away with a rotary type made for a different frequency by using a different gearing or pulley combination.

    And while we are talking about changing the speed of the load with pulley ratios, you might want to investigate just using the method to directly reduce the output speed of your motor to the desired load speed.
     
  7. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    The VFD drives seem to be the popular product because they work better than a mechanical motor/gear/generator combination. That being said, all bosses seem to want it now, cheap, and good.

    Junkyard vapor bath with hundreds of holes in the tubing, getting rain in the Freon compressor for years. "I want it rebuilt to like-new condition with the scraps laying around the shop, even if you have to solder copper tubing to stainless steel. We don't own any Freon of any type, and I don't want to pay for a compressor rebuild kit."

    I quit.
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    1,103
    To avoid saturation you may need to reduce the supplied voltage, hence the torque/horsepower, by ~25%.
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    get a vfd, there are no fixed frequency cnverts available except 60 hz to 50 and visa versa. if there were one, it would be a vfd set to a fixed frequency. all the internal componants would be the same, so the cost would be the same.
     
    #12 likes this.
  10. panic mode

    Senior Member

    Oct 10, 2011
    1,320
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    or put pulleys or gearbox to set output speed once and for all, let the motor run at rated frequency.
     
    DNA Robotics likes this.
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