PTO Generators for Tractors

Richard L. Parish  |  2/9/2005 11:31:45 PM

Figure 1. PTO generator hitched to compact tractor.

Figure 2. Electrical transfer box to allow safe switching between utilitypower line and portable generator.

Figure 3. Outdoor connection for PTO generator.

Most folks in the Gulf Coast area understand the value of home generators to keep power in their homes when hurricanes strike.
Farther from the coast, home generators are useful when ice or snow knocks down power lines. Generators are also useful for projects requiring the use of electric tools when away from an electric outlet. Although most people opt for small engine-driven generators, there are some real advantages to a generator that connects to a tractor power-take-off (PTO).

Why a PTO Generator?
Advantages of a PTO generator (Figure 1) compared with an engine-powered generator are as follows:

  • No additional engine to maintain
  • Since you don’t have to buy an engine, you can get more capacity (kilowatts) for your money
  • No need to start the generator regularly to keep it ready to run. A PTO generator can sit unused for many months and still be ready to go
  • Assuming you use your tractor regularly, it is more likely to start and run when you need it than a small engine on a generator

How About Capacity?
One horsepower equals 0.75 kilowatt (kw), so you can multiply your tractor’s PTO hp by 0.75 and get an idea of the maximum size generator your tractor can handle. Because the generator is not 100% efficient, you will probably not be able to actually deliver quite that much power. On the other hand, you can always buy a generator that is rated a little too large for your tractor and just not connect up a full electric load. If you do overload the equipment, PTO rpm will drop, causing the frequency of the current to drop and the tractor may stall. Depending on size of the tractor and generator, the system may or may not allow you to run the whole house. Typically, you will be able to run lights and appliances, but not an air conditioner or heat pump.

Safety Considerations
It is absolutely essential that you connect your generator to your house in a safe and approved manner. Most small engine-driven generators just have outlets to plug in extension cords so you can disconnect your appliances or whatever from the house circuit and connect them directly to the generator. PTO generators may also have some outlets for extension cords, but typically have one big outlet for a large 240-volt plug that can be used to connect to the house service entrance. NEVER CONNECT TO A HOME SERVICE ENTRANCE WITHOUT GOING THROUGH AN APPROVED DOUBLE-POLE DOUBLE-THROW TRANSFER SWITCH! This switch (Figure 2) will completely disconnect the home service entrance box from the utility’s power lines when the generator is connected and vice versa. This is essential to avoid your generator's feeding current back into the utility line and risking killing a utility worker who is repairing the line. It also prevents utility power feeding back into your generator when the line power is restored. Consult your utility company and use only an improved transfer switch and have the installation approved by the utility company. People’s lives depend on it! You can then wire up a cable from your transfer switch to connect to the generator (Figure 3).

Electronic Equipment
Running computers and other sophisticated electronic equipment from any generator is not recommended since the power may not be stable or “clean” enough. Don’t take the chance of ruining your computer or other electronics.

Maintenance on a PTO generator is pretty simple: keep it sheltered and out of the weather, be sure the tires are aired up (unless permanently mounted on a pad or mounted on a 3-point hitch) and grease any fittings on the powershaft or other drive components.

New or Used
New PTO generators can be expensive, but generally cost much less per kw than engine-powered generators. PTO generators are a little harder to find, but still readily available from tractor dealers and some mail-order supply companies. Some farmers have PTO generators to provide backup power for poultry houses, dairy barns, and greenhouses. It is sometimes possible to buy a used PTO generator from a farmer for considerably less than the cost of an equivalent new one. If the generator has been sheltered and cared for, it should function as well as a new one for backup purposes. Whether new or used, it is easier and less expensive to buy a generator when the weather is good rather than waiting until a storm hits and generators are in urgent demand.

PTO generators can provide peace of mind. They are far less trouble than engine-driven generators – if you already have a tractor. They can offer you more kw for your investment than an engine-driven generator.

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