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  1. #1
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    Default Braking Resistor

    G/day fella's, I have fitted a cheap VFD to my lathe, one of these https://www.ebay.com.au/itm/SKI780-5...72.m2749.l2649

    The VFD is tiny and fits nicely in the electrical box on the back of the lathe.

    It is 415 - 415 volt and 7.5 HP, the Digital inputs on the front of the VFD are switched by the forward and reverse contact relays that are no longer used to switch the motor, so the lathe Forward/Reverse lever, jog button and safety switches still work as they would normally and originally intended.

    I fitted a cooling fan to the cabinet and this is also switched on by the old 3 phase motor contractors when the motor is running in forward or reverse, also fitted a temp controller for the fan with the sensor situated at the heatsink air outlet of the VFD.

    It really is a good addition, soft start, jog button can be used now when changing gears, has any speed I want between gear ratios..... I could go on, it is fantastic........

    BUT......can anyone tell me how to get the damned brake resistor to work?

    I emailed the seller, ha, I didn't really expect much there but I thought he might be able to put me in contact with someone, and I have emailed the manufacturer in English and google translated Chinese, no reply...

    I have fitted a 1000w 75ohm braking resistor, this is the one https://www.ebay.com.au/itm/Aluminiu...72.m2749.l2649

    I have tried different program settings hoping that I would fluke getting the brake working but no joy, the brake resistor measures close enough to 75 ohms, but I have no DC power at the brake terminals when the motor is stopping.

    This manual is for the smaller kw same model VFD's and the manual is the same as the paper manual that I have. http://www.sakohz.com/download/20190124124714147.pdf
    The relevant pages that I can see are pages 30, 31 and maybe 39.

    Any advice on this would be greatly appreciated.

    cheers, shed

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    Default

    Most vfds dont come standard with the internal braking circuitry and this need to be ordered with the VFD. On the Powtran vfds the braking models have a z suffix appended to the model number.

  3. #3
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    Default

    G/day Bob, I wondered about that but the ad says

    "Features:
    1. Built-in braking unit, only need external braking resistor to achieve fast forward and reverse rotation switching."

    I am hoping the braking unit is in there????????????

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Default

    Then it will need a parameter change. Hopefuly someone will respond that knows that VFD. Sorry, Im a bit over reading yet another VFD manual 😀

  5. #5
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    Default

    Hi John,

    Check out P018 and P019 also P025.
    Check P4 (16 & 17) Don't know about (21) see Page 22 for these.
    Also 47, 48, 49 on Page 23.
    P6 (5 and 6) Page 30.
    P6 (13 and 14) Page 31.
    P9-08 Page 39

    I cannot find any more references to braking !

    HTH.
    Best Regards:
    Baron J.

  6. #6
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    Default

    Quote Originally Posted by BaronJ View Post
    Hi John,

    Check out P018 and P019 also P025.
    Check P4 (16 & 17) Don't know about (21) see Page 22 for these.
    Also 47, 48, 49 on Page 23.
    P6 (5 and 6) Page 30.
    P6 (13 and 14) Page 31.
    P9-08 Page 39

    I cannot find any more references to braking !

    HTH.
    G/day John, thanks for having look.

    P018... I have this set to 3.5 sec's as 3 sec's and below the deceleration is too fast and it gets error code 2.

    The chuck that I use on this lathe weighs 32kg so it can take a bit of stopping even without a job in it.

    P019 only adjusts the time units for P018, eg tenths or hundredths of seconds.

    All of the settings in P4 are for programing what function you want the input terminals to perform, for example I have the DI terminals wired to the old 3 phase motor relays to start and stop the motor, (and hopefully the brake) so you have a neutral DI terminal and a wire from this goes to one side of a switch/relay and the return wire from the other side of the switch/relay connects to one of the DI terminals and then you select the function from the P4 input terminals list, eg. I am using DI2 terminal for reverse so I selected P4-01 and entered number 2.

    Yes the P6 stop/start control settings are what I have been toying with, no joy there so far.

    P9-08 Page 39 It wont let me in to fool around with that.

    I think Bob might be right and it has not got the braking unit inside the VFD, I have contacted the seller again and have let him know this suspicion and if this is the problem then we need to sort it out.

    here are some pics, it is not quite finished.

    cheers, shed
    Attached Images Attached Images

  7. #7
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    Default

    Check where you have connected the resistor, manual describes a different set of terminals in the text to what it shows in the schematic.
    Look at your P6 codes, that’s where your start/stop coding is done
    Default for most of your P6 codes 0sec or 0% or 0A

  8. #8
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    Default

    I re-visited P9-08 on Page 39, Brake Unit Action Starting Voltage.

    The programing in this section are defaults that are pre set and password protected.

    P9-08 has a setting range of 700-800 volts and the default in the manual says it is set to 750 volts.

    This setting in my VFD reads 0.
    I assume it reads that because there is no Brake Unit to Act on.......

  9. #9
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    Hi John,

    Did you get any further with sorting this braking resistor job out ?
    Best Regards:
    Baron J.

  10. #10
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    Default

    Hi John, no.....nothing to report, your post just prompted me to message the seller again so thanks for reminding me.
    cheers, shed

    ps. I ordered a DRO from china, aliexpress, one month ago today, no movement on that either so I messaged them this morning
    and said that if it is not sent ASAP then i will have to cancel and look elsewhere.
    Lazy so and so's, someone sneezes and they all run and hide, any bloody excuse not to go to work

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