I’m interested in powering large woodworking machinery off the grid and am looking at the new Multiplus 48/20k. I noticed that it is rated a bit differently from most other Multiplus’s:
20kW can actually be delivered continuously (rather than 20kVA)
Peak power of only 25kW, but for 30 minutes
Most other Multiplus’s are rated to deliver roughly twice the nominal power, but for only 30 cycles rather than 30 minutes
In my case, I would be starting single phase induction motors with an FLA of up to 22A. Using the rule of thumb of 6x FLA for starting inrush current, we are at 132A or just over 30kW. Is the Multiplus strictly rated at 25kW max or can it do more for shorter time durations?
Rating is at 25C, it drops off sharply as temps get higher.
Peak power is rated for 1 minute according to the datasheet.
Sounds like you are being ambitious with transients for the unit, you also have to factor in that the battery can deal with that surge, off-grid is demanding on batteries, loads like that more so.
Can’t see any spec that would suggest a 30kW spike would be handled gracefully.
For off grid running of large machinery, I would look at replacing the motors with 3 phase units - these will be smaller, more efficient and higher torque.
A 3 phase off grid system is easy to set up, and for your application is going to be better suited than a single phase install.
The other solution would be to use an electronic soft start or VSD for the motors.
Thanks guys. It sounds like 3 phase motors and VFDs will be my best bet. In the long run it will probably be more economical than designing the system for tremendous inrush currents.