Household Washing Machines0 pages

Beyond Bits

Motor Control Edition

Household Washing Machines
Freescale MCUs provide smart solutions
for home appliances
Overview
One of the most useful home
appliances used in households
across the world is a washing
machine. Washing machine features
are still being improved thanks
to incorporating MCUs that allow
manufactures to implement many
useful features. Typical features
available in the most modern
consumer washers include:

Figure 1: Pancake PM Synchronous Motor

P
• lenty of pre-defined programs for
different laundry types
• Variable temperature settings
• Variable spin speed
• Quick wash programs
• Variable load support
• Water level control
• Delayed execution

Washing Machine Varieties
There are many types of washing
machines varying in mechanical
construction, motor types driving
a drum, a control system of the
motor control part, human interface,
level of energy efficiency, washing
performance, drying performance
and water consumption.

Mechanical Construction
1)tDrum position
t

a.tHorizontal washers
(dominate in EU markets)

t b.t ertical washers
V
(popular in US and AP markets)
2)tDrum loading
t a.t ront load washers
F
t b.t op load washers
T
3)tDrive construction
t

a.tBelt driven

t b.t irect drive
D

Motor Types Driving the Washer:
1)tVintage motor construction
t a.tSingle-phase ACI motors
t b.t ingle-phase universal motors
S
2)tModern motor construction
t a.tThree-phase ACI motors
t b.t hree-phase PMS motors
T

Control System for Motor Control
Modern control systems focus on
more sophisticated control topology
supporting sinusoidal control. One of
the most popular control topologies
is field-oriented control (FOC),
allowing for maximum efficiency,
maximum motor power, minimum
torque ripple, reduction of audible
noise and utilization of the maximum
motor torque that is required at motor
acceleration during the motor/drum
startup. The drive solution with ACI
motor requires information about rotor
speed. In the case of the PMS motor
drive, information about the rotor
position and speed is required. The
control algorithm of the PMS motor
processes the rotor position and
calculates the speed based on the
difference of the rotor position in time.
Since the position sensor is relatively
expensive, the washer manufacturers

focus on sensorless control techniques
eliminating the position sensor. The
sensorless control techniques require
powerful MCUs.

Typical Horizontal BeltDriven Washing Machines
Motor type
•t Three-phase ACIM (two poles)
•t Three-phase PMSM (eight poles)

Load capacity of standard washer
size 60 cm x 60 cm x 85 cm
•t From 5 kg up to 12 kg
•t Typically—7 kg or 8 kg

Drum spin speed
•t From 1000 RPM to 1600 RPM

Transmission ratio—drum to motor
•t From 1:6 to 1:16
•t Typically around 1:10

Motor power
•t About 750 W

Motor torque
•t About 2 nm
•t In some cases 3.5 nm

Key features of washer
applications
•t Motor control part
t

tFOC