I will be having a team drilling a water well on my property soon. Their rig is electric, single-phase, rated at roughly 5 kW (230V/20A). It’s equipped with a frequency converter.
In my system, I have two Multiplus II 48/5000 in parallel and 4 48V/300Ah batteries also in parallel and ~9 kW in solar power. It’ll have to power the rig for about 5-7 hours. The inverters, batteries and SCCs are all in a cool, air-conditioned room.
From the electrical safety standpoint everything seems fine as I have a dedicated line with 25A breaker and a differential relay for this kind of stuff, solar production will likely keep the batteries at 100% but I still worry about the inverters. Please help me dissuade those worries.
2 inverters in parallel have to be on one phase, this is different from split phase operation.
Parallel inverters do work well together PROVIDED that the AC and DC cables are the same length respectively for both inverters. So check your current balance once the rig starts. You’ll have plenty of power on a sunny day, but only about 2 hours on battery. So if the drilling takes 7 hours, looks like you could run low on stored power.
Provided the set up is done well, it will be fine.
At worst you could have an derating (but it is well sized for almost down to 50%) and overtemp shut down (hopefully not with air con).
Or the batteries can’t take the stress for the start up - obviously i can’t help as i don’t know what they are.
Frequency drives are weird animals when inverting. And they also have many variables in that set up such as ramp up time.
Other variable is of course will the 9kw of solar be at 9kw or not. I guess that will determine length of run time if all else is good.
Thank you!
I’m using this configuration for about a year. When wiring everything up, I followed the Victron guidelines and made sure the DC and AC cable have exactly the same dimensions.
My worries were mostly about how the inverters would handle such a large inductive load for a prolonged time, but judging by your reply, that’s a non-issue.
Once it’s done, I’ll add a follow-up about how things went. Wish me luck!
You’ve specifically asked about continuous use, but I would be as concerned about the startup inrush.
This is a huge unknown variable and depends a lot on the type of motor.
I have seen some smaller induction motors present themselves as “short circuit” current load to the inverter on the first start up, and this is a much faster trip time than the usual start up surge rating.
Other induction motors work great.
The frequency converter is a good sign that this has been considered by them already though.
Given how much of the cost is in time and setup for a machine like that I would have a plan B ready if the MultiPlus doesn’t do the job.
