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Hello everyone this is my first time posting here so forgive me if my post seems a little choppy. So my dilemma is trying to hook up a 2 pole three-phase DB motor rated at 230 X 3. I did a fair amount of research and thought I had the situation figured out until I got the motor disconnected from the machine and took the plate off of the junction box that is mounted to the motor and come to find 2 sets of wires each one with 1 blue, 1 red and 1 black. And another set that is wired into a brake rectifier.

Now I do have a couple questions. First do I need the brake rectifier wired in if I'm using a VFD or do I need it at all in order for the motor to run?

Also after doing a lot of reading and watching I thought I'd find 9 wires (there are 9 but the brake rectifier is throwing me off) with a diagram (no diagram) telling me which wires are what and then I'd be able to wire it up either y or delta.

Thank you.

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    \$\begingroup\$ What do you mean be "DB motor?" What do you mean rated 230 X 3?" What is marked on the motor rating plate? Do you have any external equipment connected to the motor besides the brake rectifier? What does the brake look like? \$\endgroup\$
    – user80875
    Dec 29, 2018 at 22:30
  • \$\begingroup\$ You should shrink some pictures down and show the wiring and nameplate information, but red black and blue are standard 3 phase colorings for 120/208V 3 phase, so each pair are probably the ends of a max 230V coil, of which there are 3, so if your source had 220V phase to ground, you'd set the motor up in Wye and if it had 223.45V phase to phase you'd set it up in delta. Please provide the rest of the information so we can confirm this. Do you posses a multimeter or if not that an ohmmeter or a flashlight to confirm winding continuity? \$\endgroup\$
    – K H
    Dec 30, 2018 at 0:08
  • \$\begingroup\$ When I wrote "DB" I think it means direct brake. At least that's what the information I've gathered told me. I can find the site that I gathered that information from and post a link if you'd like. Also I looked all over this thing and couldn't find any nameplate. The only thing I found was a small sticker that read "brake 230 X 3" on it. Yes I do have a multimeter. But to be completely transparent I don't know how to use it. I'm trying to with as much free time as I can get educate myself with the General basic knowledge and the correct way to make this connection. \$\endgroup\$
    – Matthew Fowler
    Dec 31, 2018 at 19:32
  • \$\begingroup\$ I'm trying to with as much free time as I can get educate myself with the General basic knowledge and the correct way to make this connection without getting myself or anyone else hurt in the process but it seems like I may have to contact a professional. Would you have any recommendations on where I can start to become savvy with these types of electrical components? Also I'm considering just scratching the VFD and going with a rotary phase converter. Would that be the smarter way to go with something like this? \$\endgroup\$
    – Matthew Fowler
    Dec 31, 2018 at 19:33
  • \$\begingroup\$ It doesn't look from the picture like the rectifier is connected to anything inside the motor. Am I mis-interpreting? Can you find if there is an external mechanical brake somewhere? Can you determine whether that brake is actually needed? Can you remove the motor to determine if there is a nameplate on it? It would sure be helpful. \$\endgroup\$
    – user57037
    Jan 1, 2019 at 3:23

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If by "DB" you mean the motor had a mechanical brake (you mentioned a rectifier), then you CANNOT leave that brake connected to the motor terminals when using a VFD on the motor, you must separate them and run separate wires to the brake coil. Then you must develop logic in your controls that will energize the brake coil BEFORE the VFD runs the motor (brake coils on motors operate against a spring applied brake, so energizing the coil RELEASES the brake). Some VFDs will include this logic capability in the VFD using an Output Relay, some (cheap versions) do not, it is up to you to investigate and implement this fully.

If you don't understand what I have just posted, you should probably not engage in applying a VFD to a brake motor...

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