Design and function
2016-03-10 / DIS 184_58300000140186_ara_en_k
Copyright by BSH Hausgeräte GmbH
Page 15 of 181
3.3.3
Commutation
Commutation is the process in which a current flow passes from one path to
another. There is natural and forced commutation.
Natural commutation is present if the feed voltage originates from an alternating
current or three-phase mains and the current path switching occurs due to its
polarity reversal.
Forced commutation is present if the feed voltage does not originate from an
alternating current or three-phase mains and the current path switching occurs by
means of a control.
EC motors use forced commutation.
Fig. 12:
Basic circuit electronic commutation
red coil = north pole / green coil = south pole / grey coil = countervoltage
The big advantage of an EC motor is that the electronic commutation can be
made dependent on the rotor position, rotor speed and torque. The electronic
commutation thus becomes a controller. The way in which the rotary field is
generated determines the characteristic of the EC motor.
Fig. 13:
Basic curve showing the torque and (positive/negative) currents in
phases L1, L2 and L3, depending on the rotation angle 0° to 360° for a
block commutation
Fig. 14:
Rotary field
red coil = north pole / green coil = south pole / grey coil = countervoltage