https://www.mycncuk.com/ General electronics discussion and anything else related to electronics. en Fri, 17 Apr 2026 02:35:34 GMT vBulletin 2 http://www.mycncuk.com/images/misc/rss.png https://www.mycncuk.com/ https://www.mycncuk.com/threads/16067-VFD-intermittently-trips-breaker-on-bypass-relay?goto=newpost Thu, 09 Apr 2026 13:11:15 GMT Hi all, I have a huayang YL-620L VFD with a 2.2Kw water cooled spindle, i am having issues with intermittent breaker trips and need to work out... Hi all,

I have a huayang YL-620L VFD with a 2.2Kw water cooled spindle, i am having issues with intermittent breaker trips and need to work out which component is to blame.

After powering the VFD via a contactor (ABB AF09) a few seconds later (~2-3) there is a 'click' sound, I believe this is the bypass relay kicking in. Sometimes this works fine and sometimes it trips my 20A breaker, not the RCD but the MCB. As far as I know this is not an inrush current issue, the point of the bypass relay kicking in there should be no noticeable current draw on a properly working unit. Is that correct ? The VFD is connected to the motor but at no point is the motor spinning when the breaker trips.

Here's the sequence of events from the other day, I wanted to check I could turn it on and off a few times without problems as i thought i had resolved the issue-
Turned on the VFD-> booted up fine. waited ~15 seconds turned it off.
Turned on the VFD->booted up fine. waited ~30 seconds (until the VFD fans stopped spinning), turned it off.
wanted to try one last time-
Turned on the VFD when the bypass relay kicks in i heard a pop sound and my contactor let out a puff of smoke. The A1 A2 coil is gone (it reads 15 mega ohms), this is the first time i've seen this and this time the breaker did not trip. This was quite a significant failure.


So it sounds like the VFD is not 'filling' up on the initial power on and the bypass relay is then creating a surge in current ?
At this point it could be a bad VFD unit, but is there a chance the spindle could be at fault or the EMI filter ?

When i first got everything hooked up, I successfully sent serial commands from linux cnc to the VFD to start and stop the motor, the motor was on for a few seconds only a few different times, but it didn't have water running through it, as there was no load on the spindle i thought this would be ok just to check it works. Could i have damaged the spindle and the actual VFD is not the issue ? Can the motor cause this issue even if it is not spinning ?

I'm in the process of moving to a 32 amp breaker but plan to put a 20 amp breaker in the cabinet to protect the house fusebox.

Any ideas or help would be very much appreciated.

Thanks ]]> General Electronics eci22 https://www.mycncuk.com/threads/16067-VFD-intermittently-trips-breaker-on-bypass-relay https://www.mycncuk.com/threads/16049-Help-needed-proofing-newbie-control-schematic?goto=newpost Sun, 25 Jan 2026 13:02:03 GMT Hi All. Is there a forum member willing to proof and amend where necessary, my control schematic for my self built CNC wood router? Regards. ... Hi All.

Is there a forum member willing to proof and amend where necessary, my control schematic for my self built CNC wood router?

Regards.

Ray ]]> General Electronics The Gresley Luthier https://www.mycncuk.com/threads/16049-Help-needed-proofing-newbie-control-schematic https://www.mycncuk.com/threads/16047-Help-Needed?goto=newpost Wed, 21 Jan 2026 13:31:25 GMT Hi All. After many many days scratching my head, trying to put together a control circuit for my SELF BUILD cnc router I have to conclude I need... Hi All.

After many many days scratching my head, trying to put together a control circuit for my SELF BUILD cnc router I have to conclude I need help.

I am not an amateur with electronics, but an advanced beginner. I am trying to put a wiring schematic together which includes at least an E Stop & Fault Trips. My CNC consists of 3, DM556T Stepper Drivers, 3 NEMA 23 Stepper Motors, a 240 vac > 36 vdc transformer, my spindle is 240 vac. I hope to be using ARDUINO UNO as controller.

Can anyone offer help and advice please.?

Regards.

Ray. ]]> General Electronics The Gresley Luthier https://www.mycncuk.com/threads/16047-Help-Needed https://www.mycncuk.com/threads/16044-Adding-Soft-Start-to-my-wood-mitre-saw?goto=newpost Sat, 17 Jan 2026 21:44:14 GMT I've been wanting to add soft start to my wood mitre saw for some time as it sounds pretty angry when it starts at full power. Well, as you can see below I finally got around to it . . . .

]]> General Electronics routercnc https://www.mycncuk.com/threads/16044-Adding-Soft-Start-to-my-wood-mitre-saw https://www.mycncuk.com/threads/16042-Where-to-place-an-E-Stop-in-CNC-wiring-Circuit?goto=newpost Sat, 17 Jan 2026 10:39:00 GMT Hi All. I have started to put my CNC router control circuit together, and I am concerned where in the circuit I should place an E Stop. I have... Hi All.

I have started to put my CNC router control circuit together, and I am concerned where in the circuit I should place an E Stop.
I have noticed the my PSU (240 vac > 36 vdc) transformer, on the 36 volt side stays powered for a few seconds, my initial thought was to place the E Stop in the 240 vac line to the PSU, If I am right this will not stop the motors dead will it due to the fact that there are Capacitors on the 36 volt rails keeping them live for a few seconds, or have I got it all wrong.

Regards.

Ray ]]> General Electronics The Gresley Luthier https://www.mycncuk.com/threads/16042-Where-to-place-an-E-Stop-in-CNC-wiring-Circuit