The Electric Drive - Pfaff 260 Service Manual

The Electric Drive
1. General
All domestic sewing machines are equipped with series motors which are
characterized by the fact that their speed is dependent upon the load. This
being so, a certain ratio must be observed between their output and their
speed.
If the motor is
too powerful for the job at hand, it is likely to disturb
the balance of the electrical system and to cause premature wear of, or
even damage to, the sewing machine.
2. The Speed
Control
The motor speed depends not only on the torque required to drive the
machine, but also on the voltage applied to the motor. This fact is used to
control the motor speed.
A variable resistor is placed in the motor circuit. This rheostat is available
as a foot, knee, or treadle control (Figs. 57-59), as may be desired by the
customer.
I
7
4
1 = Combinot1on plUg
2
=
Double receptacle
3
=
Safety pJug
4
=
Foot control
Fig. 56 Built-in Pfaff PE 370
motor
5
=
Light switch
6 =
Light bu lb with grille
(swi ng-out type)
7
=
Motor with radio noise
filler
33