Ans. It can start a load which requires much more than full load torque at starting, because the motor being nearly up to full speed, has available not only its maximum overload capacity, but also the momentum of the armature to overcome the inertia of the driven apparatus. In this it is assisted by a certain amount of slippage in the clutch, which is the case when the armature speed is pulled down to such a point as to reduce the grip of the centrifugal clutch.

Figs. 1,867 and 1,868.—General Electric disassembled clutch as used on clutch type, single phase (KS) induction motor. In starting, the armature revolves freely on the shaft until approximately 75 per cent. of normal rated speed is reached. The load is then picked up by the automatic action of a centrifugal clutch, which rigidly engages an outer shell, keyed directly to the shaft. The brass friction band of the clutch is permanently keyed to the pulley end of the armature.

Commutator Motors.—Machines of this class are similar in general construction to direct current motors. They have a closed coil winding, which is connected to a commutator.

There are several types of commutator motor, namely:

Since, as stated, commutator motors are similar to direct current motors, the question may be asked: Is it possible to run a direct current motor with alternating current? If the mains leading to a direct current motor be reversed, the direction or rotation remains the same, because the currents through both the field magnets and armature are reversed. It must follow then that an alternating current applied to a direct current motor would cause rotation of the armature.

Fig. 1,869.—Wagner single phase variable speed commutator motor. The commutator is of the regular horizontal type and the brushes remain in contact all the time. As the torque of alternating motors varies directly as the square of the applied pressure, wide speed variation may be obtained by varying the voltage applied at the motor terminals.