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Thread: Grizzly Gunsmith Lathe Break

  1. #31
    Join Date
    Nov 2006
    Location
    Augusta, Maine & Palm Coast, Fl
    Posts
    5,912

    Front

    Quote Originally Posted by alinwa View Post
    When you thread out do you prefer front or back?
    Very easy to do.

  2. #32
    Join Date
    Jul 2005
    Posts
    453
    Quote Originally Posted by savet06 View Post
    With respect to the need for an overly large VFD for a particular motor this isn't true for the units I purchased. I spoke with the manufacturers directly because I read this on various sites and it seemed counter to the websites advertising the drives. I have an automation direct drive on my mill and an Hitachi on my lathe. Both drives are matched to the motor HP within 1/2hp. According to the manufacturer there is no need, anymore, to oversize your drive. The hobby machines we are running just don't pull that much amperage, and as long as the unit you are buying covers the max amps of your motor (i.e my 2.2kw 3phase motor has a 10 amp max draw which calculates out to my hitachi drive drawing something on the order of 25 amps +/- at the breaker.) I doubt I will ever approach that level of draw and have programmed my VFD to ramp slowly over 5 seconds to avoid just that situation.
    I am not the end all when it comes to the rest of the electronics, but I did talk to the source when it comes to this particular subject. Two separate companies.
    Braking loads (current and voltage) have a rather loose connection to motor ruining current.

    The voltage especially has almost nothing to do with the running voltage.
    It is determined by the rate of collapse of the magnetic field in the motor and is actually more tightly related to the locked rotor current.

    Advertised values are almost always exaggerated.
    It is call 'advertising puffery.'

    The newer VFDs do have some newer drive devices, and may have added additional protection circuitry against voltage transients.
    When they start bragging about that and showing schematics with values I might listen.

    Thirty-five plus years in electronics design for EW fro power supplies to oscillators makes me VERY skeptical of claims without actual backup data.
    Until then they are selling you a pile of Bovine Scatology, AKA 'advertising.'

  3. #33
    Join Date
    Oct 2007
    Location
    Northwest Ohio
    Posts
    527
    I appreciate the follow up, and the information. It is so hard to separate the wheat from the chaff, sometimes, when you are a lay person. I read as much as I could and tried to glean as much good information as possible before making my decision. So far I have not been disappointed, but I wonder when the demon will rear up.
    I am actually more familiar with the inner workings of the bovine and others so maybe I'll just stick with them!
    Mike

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