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Sizing Braking Resistor For My Vfd, Need Help

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by Ayyub_Ansari, Nov 1, 2016.

  1. Ayyub_Ansari

    Ayyub_Ansari United States Iron Registered Member

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    Hello Everyone,

    I am hoping someone can give me input on sizing the proper braking resistor for my Tverter N2-202-M.
    I have extensively searched but I have not been able to find a definite answer, though I think I need a
    150w 100-Ohm resistor for my application.

    My setup is an 11" Logan Model 1922 lathe with a 2hp 3phase Dayton motor. The VFD works great and the VFDs internal brake will work for me at lower rpms but it goes into OV (over voltage) fault when turning anything with any kind of rotating mass and speed. At 60Hz (1200rpm)with nothing in my 3 jaw chuck I can set the unit to brake in 5 seconds, but I get OV if I do the same with my 4 jaw. It appears from my reading that a braking resistor would solve that issue.

    An online manual is easy to find but I can't seem to link to it from here.

    Please let me know if there is any further information I can provide and thanks to all who take the time to read and/or respond.
     
  2. hman

    hman Active User H-M Supporter-Premium

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    I have 2HP Teco VFDs on both a mill and a lathe. Both of them stop nicely with braking resistors. The Teco manual calls for a 100 ohm 150 watt braking resistor for the 2HP unit, a 70 ohm 200 watt resistor for the 3HP model. My guess is that your VFD would use the same value resistors. They're pretty standard sizes. It's the motor's energy that needs to be dissipated, and this will determine the resistor's value.
     
  3. mksj

    mksj Active User H-M Supporter-Premium

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    The braking resistor for the Teco N2-202 inverter is specified as BRN2-202, the specification is 100 Ohms, 150W (or greater) connected to the PR terminals. I often get the generic Fleabay ones that are metal encapsulate with leads, they work just fine. They do not get too hot, but I do try to mount them to a metal surface, otherwise their ratings (watts) in free air is much less. I would try to set braking to 2 seconds, maybe 3 if you have an over voltage issue. Spinning large chucks at speed often have too much momentum, and will trip the VFD error if trying to brake too quickly. On some VFDs you can program too separate braking times.The voltages on the wires can be up to 400V DC, so some care in mounting and noting the voltage requirements.

    http://www.ebay.com/itm/Aluminum-Housing-Wirewound-Braking-Resistor-200W-100-ohm-/321061356681.

    Teco Braking Resistor Specifications.jpg
     
  4. hman

    hman Active User H-M Supporter-Premium

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    OMG!
    Except for different model numbers for the VFDs, this chart is IDENTICAL to that in the Teco manual!!! Even the part numbers for the resistors themselves are the same. Go figure ... All the VFDs might well be made in the same factory in China.
    VFD Braking Resistors.jpeg
     
  5. Joe in Oz

    Joe in Oz Australia Active User Active Member

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    Tecos are made in Taiwan - there are chines copies under different names - I guess the manuals are also copied with different names..... go figure.

    BTW, I use a 75Ohm resistor on my lathe (Huanyang VFD) with 3hp motor. Sops it in 0.1 second. But only used as an emergency stop. It make the motor just about jump out of its mountings!
    My normal braking stop is 2 seconds. Tricky to set up two different ramps but possible....
     
  6. Ayyub_Ansari

    Ayyub_Ansari United States Iron Registered Member

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    It's good to know what these Tverters are cloned from. I have been very happy with the unit and the price was right at $40 (from the 'bay). I ordered a 150w 100-ohm brake and I am looking forward to putting it in service. I like the idea of setting a very fast stop for the e-stop but having a different value for normal ramping. If you don't mind Joe, I may message again for some guidance in setting it up like that (if my VFD is capable). Once installed, I will post back here on the improvements that were made by the resistor. Thanks again to everyone who gave insight into my inquiry. It was a huge help.
     
  7. CluelessNewB

    CluelessNewB Active Resistor H-M Supporter-Premium

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  8. Ayyub_Ansari

    Ayyub_Ansari United States Iron Registered Member

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    Hello Everyone,

    My braking resistor came in the mail this morning and I rushed out to put it into service. Initially looking at the size of the unit I was not too convinced that it would do what I expected. I mounted it to a piece of aluminum that I had for a heat sink(which I will mill some fins on perhaps this weekend) and wired it up. Wiring on my unit is very basic, just 2 wires on two labeled terminals and it was set up. I set all perameters on my VFD with a braking deceleration of 1.5 seconds and tested it. I am amazed at how quickly the lathe brakes now. It has no problem braking my larger 4-jaw even from 120hz (2850rpm) where before it would get the "OL" failure before, no matter how slow I was to manually decelerate on the dial.

    I want to say thanks to everyone who chimed in on this subject. You all provided me the information needed to really improve my lathe. 20161119_105804.jpg 20161119_105905.jpg
     

    Attached Files:

    FOMOGO likes this.
  9. hman

    hman Active User H-M Supporter-Premium

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    You probably won't need to add fins to the heat skink. Unless specified in the resistor's data sheet, you probably don't even need the heat sink (though it can't hurt). Remember ... the braking resistor is only used to stop the lathe, so it's a very low duty cycle application.

    Try running and stopping the lathe a couple times within a short period of time, then check the temp of the resistor.
     
  10. Ayyub_Ansari

    Ayyub_Ansari United States Iron Registered Member

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    Hman, Thanks for the input. I did out and did a series of 10 start/stop cycles at 120hz (2850rpm) and I took a reading of the temperature of the brake resistor before and after. The resistor was 64 degrees (it's 55 degrees outside where I live right now) when it was cold and it was 78 degrees after running all the cycles back to back. I am guessing that I am well within range to use this resistor without any heat concerns. Now I can concentrate of building a headstock cover for my lathe as it did not have one when I purchased it. I also need to figure out how to set up my taper attachment and collet closer but those questions (if I have any) will be another thread. Again, thanks to all who responded.
     
  11. tlangy

    tlangy United States Swarf Registered Member

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    I appreciate the VFD responses since I am experiencing similar problems on my Birmingham 3hp 3ph mill. The VFD displays OL each time I set braking parameter to < 3 seconds. Thanks for the response, I will order a BR from Ebay now and it will, hopefully, solve the problem.
     
  12. Ayyub_Ansari

    Ayyub_Ansari United States Iron Registered Member

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    I'm happy to report that the BR is working great for the month or so that I have had it. I'm not sure how i got by for so long without it and I couldn't be happier with the results.
     

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