Contactor for VFD

D

David2011

H-M Supporter - Gold Member
H-M Supporter Gold Member
Joined
May 19, 2022
Messages
391
All of this relates to the Index 645 mill I recently purchased. It has a 1 hp 3 phase motor for the spindle and a 1/4 hp 3 phase motor for the table drive. If you think I'm overcompl;icating it, let me know.

Initially I am only connecting the spindle motor. Once the spindle is running and the control box is set up to my satisfaction I'll get another VFD for the table motor. The reasoning is that if the first VFD is too small it can be used for the table and a bigger one purchased for the spindle. The VFD I bought is a GS20 from Automation Direct. The plan is to bring 230VAC single phase into the control box and split it off to a 230V side for the contactor and VFD and also 115 VAC for machine lighting, DRO, control box cooling fan and any other miscellaneous low amperage 115V requirements. The 230V main is coming into a Westinghouse 20A DIN breaker. The output goes to the contactor and to a 115V Westinghouse breaker for the miscellaneous 115V requirements. My question is regarding contactors and possibly using a thermal overload relay. Automation Direct recommends thermal overload protection but I'm wondering how necessary it really is. I'm not one to push a mill to its power limits because I pay for the end mills out of my own pocket. I've been diligent to use US brand names (even if the actual product is made offshore) for the breakers and VFD so I'm trying to stick with a reasonably budget friendly US branded contactor and thermal overload relay like Siemens or Schneider rather than some unpronounceable brand from Amazon.

My choice is to use a magnetic contactor for the safety of not restarting unexpectedly if I pop a breaker. Several other tools in my shop are equipped with magnetic switches and I like them. For those using a magnetic contactor with an integral coil, what are you using? Are you using thermal protection? If so, please provide part numbers. I'm having little success matching a Siemens or Schneider contactor to a coil (120V) and thermal overload relay as a bolt-on group.

Just for reference, I'm retaining the original drum switches to control the forward/stop/reverse of the spindle and table by connecting them to the VFD with small gauge control wire. I just didn't think it felt right to control the motors from a VFD pushbutton panel.
 
I used a mag contactor to fire up my Hitachi WJ200 for a 5 hp lathe and blew two of them up over a period of a few months. Mark Jacobs had done the build and suggested I change to a spring loaded manual switch. I don't know the why or how but the problem stopped so I now only use manual switches. I don't know if the problem was specific to my mag contactor but too expensive to experiment with.

Dave
 
markba633csi said:
What are you concerned about starting unexpectedly? The VFDs will shut down if there is a fault
Click to expand...
The contactor would control all power to the mill and all accessories. If I pop a circuit breaker and forget to turn off the mill I don't want anything starting up because I forgot to power it off. It's just a personal preference.
 
Beckerkumm said:
I used a mag contactor to fire up my Hitachi WJ200 for a 5 hp lathe and blew two of them up over a period of a few months. Mark Jacobs had done the build and suggested I change to a spring loaded manual switch. I don't know the why or how but the problem stopped so I now only use manual switches. I don't know if the problem was specific to my mag contactor but too expensive to experiment with.

Dave
Click to expand...
Interesting. There are lots of contactors in service without issues but this is worth remembering. Thanks.
 
Yes, It may have been specific to the contacts. As to powering back up, if the power goes out and comes back on, the vfd will energize but not start the mill up. Dave
 
David2011 said:
The contactor would control all power to the mill and all accessories. If I pop a circuit breaker and forget to turn off the mill I don't want anything starting up because I forgot to power it off. It's just a personal preference.
Click to expand...
You can do that if you like but the VFD should not restart automatically as long as the parameters are set that way.
 
For my lathe, I used a 12 pin relay that I wired to latch and a 6 pin as part of the control circuit. If the power goes out or the E-stop is pressed, the relay unlatches and kills drive controls and a contactor on the drive output. I have to push a start button to reset the relay, but the direction/run switch has to be in the stop/neutral position for it to reset.
 
markba633csi said:
What are you concerned about starting unexpectedly? The VFDs will shut down if there is a fault
Click to expand...
Yes, exactly. No need for a contactor.

I would suggest a 3 pole motor switch. Use 2 poles for the two hot lines and the third for the neutral.

I just installed the 2 pole 40amp version of this 30amp motor rated switch to turn off power to the VFD on my 7.5hp radial arm saw (I don't like leaving the VFD running when I am not in the shop). If the power blinks out then comes back on the VFD will power up but the radial arm saw will not be energized until I push the start button for the VFD.

Screenshot 2023-12-20 033443.png

The switch has a substantially larger and meatier lever than a light switch and it clicks (clunks) with much more authority but it fits in a standard junction box and a standard switch plate fits fine (I didn't think a standard switch plate would fit but it does).

All of my VFD's have to be specifically programmed to power on the motor when the VFD gets power. None of them default to this mode from the factory.
 
Last edited:
I don't see the need to interrupt the neutral, but that does look like a beefy switch. The two pole is only 20$
 
Last edited:
You must log in or register to reply here.
Back
Top