29 of 61
Indesit
Company
Service Manual UK
English
COMPONENT FUNCTIONS
Stepper Motor Characteristics (for the damper and dispenser motors)
Stepper motors operate differently from normal DC motors, which rotate when voltage is applied to
their terminals. Stepper motors, on the other hand, effectively have multiple "toothed" electromagnets
arranged around a central gear-shaped piece of iron. The electromagnets are energized by an
external control circuit, such as a micro controller. To make the motor shaft turn, first one
electromagnet is given power, which makes the gear's teeth magnetically attracted to the
electromagnet's teeth. When the gear's teeth are thus aligned to the first electromagnet, they are
slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is
turned off, the gear rotates slightly to align with the next one, and from there the process is repeated.
Each of those slight rotations is called a "step," with an integral (complete number) number of steps
making a full rotation. In that way, the motor can be turned by a precise angle.
Compressor
The compressor is managed by the power module and switches on whenever a demand for cooling is
received.
There are situations of cooling demand in which the compressor remains off. These are as follows:
1.
Compressor protection:
the compressor switches on once a minimum safety time lag has
elapsed since the last power-off, thereby allowing the refrigerant gas pressure to reach a point of
equilibrium in the refrigerant circuit. The same minimum safety time is observed in the event of a
mains power interruption (voluntary or involuntary). This compressor protection strategy is
observed only after the product has been operating continuously for the number of hours defined
in the module memory.
2.
Pause after defrost:
at the end of the defrost cycle the compressor observes a protection time
parameterised in the module memory so that the water formed during the defrost can be
completely drained.