Trying to make motors control, but have very significant influence of the motors between each other. When first motor is stopped (by built in limiter) second one (stopped) start turning cca 1/4 of turn (ignoring built in limiters and can create lot of damage). The relays wiring and MCU commands are correct, tested many times, with one motor everything is perfect.
My assumption is that there is problem with the motors creating strong feedback voltage. I have read a lot about RC snubbers, but have seen at least 10 ways of calculation, leading to different results and do not know which one is correct. I here someone who can help with designing such a circuit? Will the circuit help at all?
Please have look at my schematics below. (only 220V part displayed)
Relays (even the MCU ones) always have 220V coil and also contacts. MCU switches them via own relays not displayed in schematics. Blue marked ones are common, because if not having the correct signals can result in physical damage so I do not want to rely on MCU and SW.
Motors have cca 0.55A when operating but depends on which wire you drive (I see variations on multimeter, but have no osciloscope). Motors are controlled by switching live to one or multiple inputs and have own position switches build in that are part of hw layout, have no documentation and can not be accessed (in schematics not displayed they are inside the M1, M2 circles). Relays have contact capacity of 10A so it should be fine.
The red markings ?1(coil), ?2(contacts), ?3(motor) represent positions where maybe RC snubber is needed, but have no idea where and how to design them. Should they be capacitor + resistor or TVS... Varistor I do not want as they degrade over time. Relays change position cca once in 5 min, but I need it to be robust, do not want to hear about it for next 10 years :-)
Summary what I have until now:
- Cap+Resistor fails to short not such a good idea, and capacitors are short lived elements
- TVS seems better, but I can not find anything with performance, max is 1-2 watts :-(
- Calculation for RC: https://electronics.stackexchange.com/a/162137/215231, How to calculate Snubber for different load value
- TVS selection found limited information on power sizing and do not know if Stand-Off Voltage is in RMS or peak?? http://www.protekdevices.com/xyz/documents/kb/tech/ta1020.pdf usually they calculate us for peak, but because the other motor can turn 1/4 of turn it is much longer peak.
I have build few ideas with DC, raspberry pi, NRF, Arduino and know a little about DC, but absolutelly nothing about AC.
I tested everything with MCu and also manually connecting. Driving circuit is correct, error is in engines they must send some bad currents back.
The L in schematics is live, N is neutral and PE is 'second' neutral. the 2 neutrals are either way connected so no big difference.
