I'm wanting to fast switch a 1kw AC load (hot water heater) to be effectively 500w at a rate of maybe 20-50 times per second using SSR and arduino.
Will this fast load pulsing on/off damage the inverter (Multiplus 3ooo) in any way?
asked
Effect of fast switching of load (PWM) on inverter?
Hmm, no-one have any ideas on this?
Low speed PWM (around 20 to 50 Hz) is not a great idea - it will cause the AC waveform to be distributed, any lighting connected at the same time to flicker and the Multiplus to humm/groan.
That said, if your only switching 500W from a 3000W Multiplus it might be bearable, but still not a great/ideal long term solution.
There are some AC motor speed controllers that switch AC at ~1000Hz which might be OK, but I have not tested myself.
The ideal solution to control AC output power for a heater is to use something like the My PV-AC Thor unit https://www.my-pv.com/en/products/ac-thor, which does not disturb the AC waveform at all. You can also control the power output continuously via Modbus TCP, frequency shift or other methods of integration.
Thanks Mark,
My other option is to use as small an element as I can find (1.5Kw for this particular solar hot water cylinder) and turn it on and off every few seconds depending on battery strength.
As I'm generating 1kw and the element is 1.5kw the idea is to wait until battery is 90+% charged, turn on the element for 5 seconds and then off, then constantly resample battery state of charge until it is back up over 90% and repeat.
I'm currently doing this with an arduino but with the timing of 15 seconds, which is sometimes depleting the battery too quickly so I think 5 seconds would be better (I don't want to cycle the battery bank if I can help it). If this is constantly switching the 1,5kw load on and off every few seconds what impact would this have on the inverter and batteries, or would they handle this fine?
