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Thread: Will a VFD output single phase?

  1. #21
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    Quote Originally Posted by in2steam View Post
    Ian,
    If you connect a single phase motor to a VFD and disconnected the start winding it would just sit there and hum
    In a sales brochure for Optidrive E2 (available here) is the following language:

    The Optidrive E2 Single Phase is the world’s first fully digital, fully
    packaged variable speed drive for controlling low power single phase
    motors.
    Designed to be cost effective and easy to use, the Optidrive E2 Single
    Phase is for use with PSC (Permanent Split Capacitor) or Shaded-
    Pole Single-Phase induction motors.

    Seems to me the price is reasonable, and it looks to be able to allow speed control on a standard lather motor...

    Is there something I'm not understanding?

    Regards,

    CNC_Hacker



  2. #22
    Community Moderator Al_The_Man's Avatar
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    If you notice they mention Permanent split phase induction motor, this applies to to types that have the phase shift capacitor connected in both start and run, as opposed to the type that just used the cap for start only.
    The permanent split phase are often low power or fan usage etc. Shaded pole the same.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  3. #23
    Member handlewanker's Avatar
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    When all else fails and you just gotta have speed control, using one of those variable pulley drives takes a lot of beating.

    Some years ago the firm I used to work for in UK was engaged in the rebuilding of cigarette making machines, (yaaaa boooo hisssss, enviro idiot.....etc) oh well it was their bread and butter, and at the same time I was able to scavange a whole load of bits and pieces that otherwise got thrown in the scrap bin.

    One of the "bits and pieces" was a pulley about 75mm diam that had a spring loaded flange to vary the diam of the belt groove, and used an A section belt, (about 15mm wide at the top of the V).

    The belt rode in the pulley groove at the 75mm diam and by applying tension to the belt made the flange under spring pressure move sideways so causing the belt to ride deeper to the 45mm diam, thus effecting a variable pulley diam.

    This method is also used on the Bridgeport mill and possibly others too, to effect an infinately variable speed change whilst the machine is running.

    The Bridgeport type has large diam pulleys about 300mm, or thereabouts, and a special wide belt, but works very smoothly.

    The beauty of the variable belt drive is you get an increase in torque as you slow the output speed, without slowing the motor, whereas the motor speed control, if used to slow the motor down, does so at the expense of increasing the power to the motor to get the torque, often leading to overheating.

    The main interest in three phase motors is they are so cheap in scrap metal yards due to only being used in industry, and have very little value to the DIY person who only has a single phase supply.

    The other thing about 3 phase motors is you can load them up to the hilt and only blow a fuse whereas a single phase motor would probably burn the start windings out when approaching heavy loading.

    Just for the record, I dumped all my single phase 1/4 HP, 1/2HP motors in favour of 3 phase for the above reasons, but mainly after I invested in a 1HP VFD unit for about A$200.

    If you can get 3 PH motors at a cheap price then the VFD is the way to go without a doubt, also depending on the size of the motors and your mains, but in the range up to 1HP is a very handy set-up price wise, but as the HP rises so does the cost of the VFD.
    Ian.



  4. #24
    Community Moderator Al_The_Man's Avatar
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    I happened to be picking up a 25hp VFD from my WEG supplier last week, he showed me the latest VFD's they have which if used with a WEG motor guarantees 100% rated torque down to 1 rpm without the use of fan cooling.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  5. #25
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    Quote Originally Posted by handlewanker View Post
    When all else fails and you just gotta have speed control, using one of those variable pulley drives takes a lot of beating.
    VARIABLE PULLEYS...

    SCRAP 3-PHASE MOTORS...

    Excellent advice, all of it!

    Thank you, very much for your reply...



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Will a VFD output single phase?

Will a VFD output single phase?