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What size generator do I need to milk?
Check off what has to run during an outage. You'll get a generator size and how much tractor it takes to turn it.
How this works
The math
A running motor uses about 1 kW per horsepower.
Starting one takes about 3 times that, for a second or two.
The generator has to carry everything that's running plus the biggest motor starting. A VFD starts the motor gently, so there's almost no surge.
Tractor size
Plan on 2 PTO horsepower for every kW of generator.
A tractor that's too small bogs down. That can damage motors and electronics.
PTO generators turn at 540 or 1,000 rpm. Match yours to your tractor.
Make it go further
- Start the biggest motor first, then the rest one at a time.
- Run the water heater after milking, not during.
- Three-phase motors need a three-phase generator. Most PTO units are single-phase, so ask before you buy.
This is an estimate for planning. Real motors vary. I take readings on your equipment before I size a generator or a transfer switch.