Starting Large Motors with Alternative Power Sources

Woodworkers consider the problem of starting up big equipment in a solar-powered and wind-powered cabinet shop. November 30, 2009

I run a one man custom shop and we run off solar and wind power. I have a new machine that is too large at start up for my inverters, unless everything else is turned off. Is there an aftermarket add-on soft start device that would lower the amps it takes at start-up? After one second the inverters have more than enough juice in them to get the job done but that first second is asking everything of them.

Forum Responses
(Cabinetmaking Forum)
From contributor L:
Cheapest solution may be a Y- Delta starter. They require a 6 lead motor. They come standard on a lot of European machines. Real soft starts for larger motors get pretty expensive and can be had at most industrial electric supply houses. You might check with

From contributor B:
I have no info on your soft start issue, but I'm acutely interested in your alternative energy production. Any chance you could expand on what your system is all about? It seems from my research that the cost of a system is way beyond feasible even for a typical household. I'm amazed you are able to run any sort of woodworking machines... at least without having to do it under candle light.

From the original questioner:
I live in one of the most remote areas in the lower 48 states. Power was going to cost around 30k to bring in and for roughly that amount we have set up a system large enough for a one man shop and the house (well, it was plenty until this week!). We currently do supplement our power on work days by running my little Honda 5000W generator for a couple of hours because I'm a cheapskate and haven't been willing to fork over the last 6k in solar panels that will make us truly independent. I guess it hurts less in $30 weekly increments of gas! I run a table saw, hinge boring press, midsize hot air bander, small spray booth, miter saw, along with all of the house (well pump, freezer, fridge/freezer, various computers and TVs, etc.) plus lighting for the both house and shop.

Roughly I have in it so far:

5k for the best batteries you can buy
5k for two inverters (two for running 220)
5k for various other controls and shipping
6k for solar panels
750.00 for a small wind generator
3k for a Honda generator

Please understand I set it up myself and I'm sure that saved me a pretty penny. It definitely takes a little more thought to make it work. But I'm as independent as they come (had little to do with being "green") and I take pride in the system.

From contributor R:
If you can you connect a small pony motor to it to get it spinning first, that should lower the amp draw on startup.

From contributor T:
For much less than the cost of true soft-start for a larger machine, could you incorporate a smaller generator and dedicate it to the start-up of the larger machine? It doesn't fit with the independence of living off-grid, but it would only need to supply start-up amperage for a very short period of time. Just a thought. Or have I missed the point entirely?

From contributor U:
Could you post your hp requirement, voltage, and if it's single or three phase? There are a few direct wire in after the starter styles (older). You could also just swap the starter you have for a new direct replacement starter. Or you could move to a variable frequency drive. You have a lot of options. The vfd would be your best bet, but not your cheapest. It would definitely help you with your power management. You can almost indefinitely control your speed, power, etc. I have to agree about checking with

From contributor L:
I made an assumption that your larger motor was 3 phase (re: 6 lead motor & Y- Delta.) I'm just used to dealing with production equipment. Not that a solar powered system couldn't be 3 phase. I think it is also possible to use large capacitors for a short burst to start the motors turning.

From contributor U:
I also made the same assumption at first. If your motor is single phase, your options shrink dramatically.

From contributor E: sells (along with tons of other people) single phase ac variable frequency drives. If you use one of these to ramp the motor up to speed over a second or so you will avoid the inrush that is tripping your inverters.