d.

_Flexible Power_

An electric motor is an extremely satisfactory form of power because
it is so flexible. Thus, one may use a five horsepower motor for a one
horsepower task, and the motor will use only one electrical horsepower
in current--just enough to overcome the task imposed on it. For this
reason, a large-sized motor may be used for any operation, from one
requiring small power, up to its full capacity. It will take an
overload, the same as a dynamo. In other words it is "eager" for any
task imposed on it; therefore it must be protected by fuses, or it
will consume itself, if too big an overload is imposed on it.

A one horsepower shunt or compound motor is very serviceable for
routine farm operations, such as operating the separator, the churn,
the milking machine, grinder, pump, and other small power jobs. Motors
of 1/4 horsepower are handy in the kitchen, for grinding knives,
polishing silver, etc., and can be used also for vacuum cleaners, and
running the sewing machine. For the larger operations, motors will
vary from three horsepower for cutting ensilage, to fifteen horsepower
for threshing. They can be mounted on trucks and conveyed from one
point to another, being fed current from the mains by means of
suitable wires wound on reels.

Remember, in estimating the size of your plant for light, heat, and
power, that it does not have to be big enough to use all the devices
at one time. Also remember, that two water horsepower to one
electrical horsepower is a very liberal allowance; and that a
generator working under one-half or two-thirds capacity at normal
loads will require less attention than a machine constantly being
worked above its capacity. Therefore, let your generator be of liberal
size, because the difference in cost between a 5 and 10 kilowatt
machine is not in proportion to their capacity. In fact (especially
among second-hand machines), the difference in cost is very small. The
mere fact that the generator is of 110 electrical horsepower capacity
does not require a turbine of 20 horsepower. The chances are that
(unless you wish to heat your house and do large power jobs) you will
not use more than 3 to 5 electrical horsepower normally; therefore an
allowance of 10 water horsepower, in this case, would be ample. A
plant used simply for lighting the house and barn, for irons, and
toasters, and one horsepower motors, need not exceed 2 or 2-1/2
kilowatts for the generator, and 5 or 6 hors