I have a device (metal cleaning/polishing machine) which needs to switch between AC and DC outputs for its different modes.
The input is coming from a 24 Vac transformer which needs to either be routed directly to the output, or routed through a bridge rectifier -> smoothing circuit -> output.
The difficulty is that it needs to be switched digitally using a PIC. So physical switches with high current/voltage ratings are out of the question.
Currently, I'm using two SPDT relays but they just aren't reliable, as the output peaks at around 24 Vac 50 A and around 34 VDC 35 A. It seems like trying to find relays which can handle switching both AC and DC loads on this scale is an impossible task, especially with current stock shortages across all components. I'm currently using these but have had a few failures with them. The relays are never switching under load, they only switch when the load is disconnected.
Solid-state relays could possibly be an option, but the price for relays with this rating is way too high.
I was thinking about some sort of MOSFET configuration, with a push-pull for the AC signal (as shown above), and just a single MOS for the DC signal. The issue there is that I'm just not 100% on how to configure the hardware so that I can switch between the AC mode and the DC mode. The simulation above isn't accurate to the system in terms of timings, the relay switching will only happen when the mode needs to be changed by the user (probably once every few minutes).
Any ideas would be a great help. Cheers.