0
\$\begingroup\$

I'm trying to control an AC motor with an ESP32. Here it is the schematics on https://falstad.com. I've simplified the AC motor coils with 2H coils, maybe I should place a resistor to make it more realistic but I'm not sure if that would change something for this question.

enter image description here

I've found several problems which I don't know how to solve:

  • The Main Circuit Breaker goes off every once and then (I've even burned some low isolation relays). I'm almost sure this is because of voltage spikes when switching on and off the relays which powers the motor. Playing with falstad it seems that depending on the current phase, the voltage could raise up to some thousands of kV. I've been searching on how to place a snubber, found question here Designing a AC Snubber circuit for 2 hp using AC snubber but I'm not sure on how to place it in this circuit. I'm asking if someone could help me to place it, any example circuit or falstad schematic would be very helpful.

  • I'm not sure if this circuit is introducing some harmonics/interferences or reactive energy, in this case, how could it be corrected?

  • The controller is placed inside a garage with some old neon lights. When switching off some of the neon lights, suddenly the motor starts spinning. I'm not sure on what could be done in order to filter the interferences. Also not sure on how to detect them and who is being affected, if it is the relays or the MCU.

EDIT

Schematics:

enter image description here

Layout, this is approximate, as for the prototype I'm wiring with manual soldering with cables:

enter image description here

\$\endgroup\$
12
  • \$\begingroup\$ Welcome! "When switching off some of the neon lights, suddenly the motor starts spinning." EMI issue. Show schematic and layout. Snubber across the relay contacts comes to mind too. \$\endgroup\$
    – winny
    Commented Jun 9, 2022 at 13:53
  • \$\begingroup\$ Thanks @winny, I've shared the schematic here: oshwlab.com/miqmago/motors_brico, layout done by hand with cables and grid pcb. The EMI filter is a proposal (never tried), I've started reading about it from your comment, but not really sure about C and L values, help very welcome... Also for the snubber, as I'm not sure on how to design it and the values for R, C and which varistor could be used. The circuit is little bit more complex: UP_DOWN inverts the motor direction by switching the connection between the coils. Also I've been thinking to use 12V for relays and get better relays \$\endgroup\$
    – Miquel
    Commented Jun 10, 2022 at 22:39
  • \$\begingroup\$ another option I've been thinking is to use some commercial option like this one for EMI filter \$\endgroup\$
    – Miquel
    Commented Jun 10, 2022 at 22:40
  • \$\begingroup\$ Please embed your layout in the question. How many layers are you using? \$\endgroup\$
    – winny
    Commented Jun 10, 2022 at 23:09
  • \$\begingroup\$ @winny added layout and schematics, for the prototype I'm manual soldering everything with cables, so I could not talk about layers as there are no layers at all. In the schematics I've designed what I think it could work: the EMI filter and a new power source for 12V relays, it would mean to use different relays too... So thanks to your help, now the main questions are: Would this EMI filter work in terms of not breaking anything? How to place a snubber circuit (values for R, C and varistor and how to connect them)? Makes sense to use 12V relays, would it change anything? \$\endgroup\$
    – Miquel
    Commented Jun 13, 2022 at 8:05

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.