Ideas to suppress inrush current seen by my electric meter??

Thought I might throw this out to see if anyone has some good ideas here. Basically I am moving to an area where I only have single phase power. No biggy, I build rotary phase converters and know how to get around most of their pitfalls. However, a major issue is the power company ALSO dictates they do no want any more than a 10hp motor on the line. Now, they do not go into any more detail than that. Even VFD controllers, soft starts, etc.

With the day of smart meters, they will be able to see my inrush, and I need to be able to run a couple 30HP motors, on VFDs. Since I will have 600A of power, technically I have enough current, it just comes down to their inrush issue. Now, I could ramp the motors up slower and they would never see it, but the motors need to accel/decel a LOT and I want to get things done.

Bottom line is I would certainly exceed the inrush of a typical across-the-line start of a 10HP motor. I am looking for a way to sink or tank power up, or otherwise snub the inrush that the poco sees. I considered adding additional capacitors in the VFDs, which WILL work, but when I calculated the acceleration rate I need, and estimated current, the qty of capacitors and costs got to be simply insane. like 100 capacitors at a cost of about $10k! That does not seem like a solution.


Before anyone metions just paying for 3Ph power, it simply is NOT available for any less than 6 figures.

At this point, I am almost open to building my own power station, running a huge genset, etc. I will need this power a LOT and I know a genset will be loud, inefficient, etc, etc.

What about adding electronic clutches to the motors so they don't have to start and stop?

Tough problem. I'll throw out motor-generator with flywheel. That was how my University's computing center was powered.

30 HP Eek!

So, you COULD get the motor-generator up to speed slowly and hopefully the flywheel would remove the hiccups/

Not sure if this https://ieeexplore.ieee.org/document/218864/ paper would help or not.

A solution seems very expensive.

The motor-generator with flywheel seems like it would be the most straight forward approach to maintain the power levels that you want on startup where the flywheel would maintain an average power once it was up to speed.... that said it may not need to run continuously once your 30HP motor is up and running unless there are frequent stop starts.

If you can sacrifice startup speed, then an inrush current relay or series of them might work if designed properly where the "open contacts" still provide a significant load but limited with a dummy load in series with the 30 HP motor. 30HP on an induction motor is about 45 to 50 Amps ... which is within the capabilities of an inrush current relay.

I did a similar design with a heater element to keep it from tripping the breaker box. The heater element was on a machine that can accept 110V or 220V, however operation under 110V cause the heater to take 4 times as long to heat. I had a boost circuit when 110V was detected that supplied 190V to the heater ... the inrush current draw was about 30 Amps, but because it was a heater element, the "startup speed" wasn't much of an issue... just that it was faster than nothing at all under 110V operation.

You make no mention of your Industrial Line Voltage? I would be thinking about a capacitor bank as while you discount it, it is in fact a normal viable solution. Calculation of Inrush Currents in Single- and Multi-Step Capacitor Bank Installations is a good start. I can't imagine too many industrial rental properties which lack 3 phase industrial power 480 VAC Wye or Delta power nor the power limitations you mention.

Ron