help needed from downunder

Discussion in 'General Electronics Chat' started by ozzytim, Aug 22, 2009.

  1. ozzytim

    Thread Starter New Member

    Aug 22, 2009
    6
    0
    G'day guys,
    i'm new and need some help .
    1.I brought a a electric sander with a brushless ac motor from the U.S it has a rating of 115V 60 Hz 10 amps.
    I'm told by other owners of this machine that it has burn out circuit boards.Why ?they don't know.pic of machine http://www.fatandys.com/literature/B...AdvantEdge.pdf

    2.my power supply here in Aus is 240V/50 Hz.

    I was going to buy a vfd to change the aust supply to the machine spec's
    the vfd i was thinking of is this http://cgi.ebay.com.au/Variable-Freq...d=p3286.c0.m14

    after writing this question it has occured to me that maybe the circuit board in the machine is type of vfd?
    Can someone please help me?
    ozzytim
    [​IMG]
     
  2. ozzytim

    Thread Starter New Member

    Aug 22, 2009
    6
    0
    Alberto,
    My machine is single phase.I can get a transformer 2kw but i'm worried about the frequency from 60 to 50 hz.

    Do VFD only work for 3 phase?
    tim.
     
  3. ozzytim

    Thread Starter New Member

    Aug 22, 2009
    6
    0
    Alberto what about the frequency?
     
  4. ozzytim

    Thread Starter New Member

    Aug 22, 2009
    6
    0
    Hi Alberto I did contact them with the following reply:
    1.Quote
    Hi Tim
    It is right that the Advantedge is a 115V/60Hz machine, made only for the American market.
    I don't think it will work. At least not very long... We have not tried it in our lab, but the frequency (Hz) is what normally controls the rpm's.
    The Advantedge has a "brushless" motor, meaning there are no carbon brushes.
    The speed and load is controlled by an electronic card.
    My guess is that the card will go "bananas" when it don't recognize the proper power.
    But, feel free to try. Just remember that any warranty is not valid, if you do.

    Good luck.
    Toni Müller
    Leader Technical Support Sales Area Nordic

    I did read on another forum to use 92v/50hz.
    2. Quote
    Operating at 50hz will slow the rotor.The speed of an induction motor is given by 120*frequency/no pole of motor less 4% for full load speed.

    The BIG problem comes when you transform the voltage to 110v ac 50 hz. This violates the rated airgap flux of the motor and results in magnetic saturation giving rise to EXcessive heating!!!!

    To overcome this the voltage/frequency ratio must be maintained as the frequency is changed. A typical VSD does this in ausie slang we calll them VVVf drives ie variable voltage variable frequency drives.

    to fix your problem your motor's native volatge frequency is 110v/60 must equal ?/50

    ?=92V if you fed your compressor 92V@50hz via a cutom made transformer it will work perfectly.The speed will be lower but the motor will be more energy efficient as its iron losses are lower when operated at the corect voltage at reduced frequencies."


    Do you think that 92volts would be to low?
    Thanks for all your help
    Tim


     
  5. ozzytim

    Thread Starter New Member

    Aug 22, 2009
    6
    0
    I'll try to get a circuit diagram and post as you said
    Thanks for your help mate
    Ozzytim
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    How much is this gadget? This could be a case where the solution is more expensive than the applience.

    My 1st thought is a UPS myself, but then the paragraph above explains why this might not be a good idea.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,672
    899
    Considering the shipping expense, it is probably not cost effective to return anything to the USA. Here are some additional thoughts on the subject:

    1) VFD's often run from 3-phase, but not all of them. In fact, they are a cost effective way to go from single-phase to 3-phase in the USA. And in the bargain, you get speed control. In other words, when you get a VFD, look for one that is single-phase powered.

    2) Some VFD's will go to more than 100%. The KB model KBVF will go as high as 200% --120Hz--, I believe. In fact, depending on the controller, you may be able to switch select the output frequency (see: KBVF installation instructions, pp. 2 and 5).

    3) The VFD may allow you to use a single phase of the output to power your step-down transformer to get the 110VAC (approximately). The KBVF manual is silent on that possibility. There might be feedback from the other phases. The manual is also quiet on powering a transformer instead of a motor. Again, feedback may be an issue. My personal experience with KB tech service has been good. I would suggest calling it about the above issues, if you decide to try that approach.

    4) The letter you have from the manufacturer is probably accurate, but not complete. I suspect there is a great deal of C.Y.A. involved.

    5) Anacon specializes in motor speed controls for SINGLE-Phase motors. That is, single-phase in, single-phase out. Here is a link to one of their manuals: http://www.anaconsystems.com/data/manual_e2_s.pdf

    I have one of their controls that I tried on a single-phase motor. Torque was terrible, so I didn't use it. However, something like that may work for frequency conversion for a brushless motor.

    6) A motor-generator solution will certainly work, but seems to be an expensive and heavy solution to the problem.

    Finally, item #3 would be of greatest concern to me in using a three-phase VFD controller. Anacon's single-phase converters (or similar devices from other manufacturers) may work, but my first step would be to simply try your sander on 50 Hz, as suggested above, and see what happens.

    You mention that the sander may be inoperative to begin with. That is a problem. How will you know whether your power supply or the sander is bad, when smoke appears?

    John
     
Loading...