Drive Motor Circuit; Temperature Sensing Circuit; The Heating Circuit - Electrolux 6000 Service Manual

Drive Motor Circuit:

When power is connected to the dryer, line 1 is applied
to the COM terminal of the door switch. When the door
is closed, the COM terminal is connected to terminal
NO of the door switch. From terminal NO, power is
applied to terminal J4-2 of the control board to the motor
relay RL 1 on the control board. When the control board
closes relay RL 1, power is applied through terminal J4-
1 to terminal M4 of the drive motor.
Terminal M4 is connected inside the motor to one side
of the thermal overload (The thermal overload protects
the motor from being damaged by overheating.) The
other side of the thermal overload is connected to one
end of both the run winding and the start winding of the
drive motor. When the motor is not turning, the other
end of the start winding is connected internally to terminal
M5 of the motor through the NC contact of the motor
centrifugal switch. The other end of the run winding is
also connected internally to terminal M5 which is
connected to neutral.
When the motor is not turning, the start winding and the
run winding are connected in parallel. When the contacts
of relay RL 1 are closed, with the dryer door closed, line
1 and neutral voltage are applied across both the start
and run windings of the drive motor. With power applied
to both the start and run windings, the motor starts to
turn.
When the speed of the motor reaches about 80% of it's
normal run speed, the contacts of the centrifugal switch
remove power from the start winding thus removing the
start winding from the circuit.
The drive motor preforms two tasks in the dryer. A pulley,
attached to one end of the motor shaft, uses a belt to
drive the dryer drum. The blower wheel, attached to the
other end of the motor shaft, pulls the air through the
clothes and forces it out the exhaust vent.

Temperature Sensing Circuit:

The temperature in the dryer is controlled by the control
thermistor and the electronic control board. The control
thermistor is mounted in the blower fan housing. The
thermistor is a negative coefficient thermistor that
decrease in resistance as the temperature increases.
The electronic control board reads the resistance of the
thermistor and converts it into temperature. The electronic
control compares the reading from the thermistor to the
temperature setting for the cycle and cycles the heating
circuit accordingly.

The Heating Circuit:

The electronic control board applies power to the heating
circuit through the contacts of relay RL 2. When the
electronic control senses that the temperature in the
drum is below the programmed temperature, it closes
the contact of heater relay RL 2 applying line 1 to the
high limit thermostat. The high limit thermostat is a
safety device that prevents the dryer from overheating if
the contacts of the relay RL 2 fail closed. The contacts
of the high limit thermostat, normally closed, are set to
open at a temperature above the preset temperature
specifications of the electronic control board. From the
output terminal of the high limit thermostat, line 1 is
connected to pin 3 of the eight pin plug, one side of the
holding coil of the gas valve, the secondary coil of the
gas valve and the sensor that is mounted on the burner
chamber.
The connection to pin 3 allows the control to monitor
the contacts of the high limit thermostat and An error
code will show if contacts open above a preset number
of times in a cycle.
The holding coil, secondary coil, booster coil, sensor
and igniter circuits interact with one another to assure
safe operation of the dryer gas burner.
The gas valve has two chambers in series, both must be
opened before gas will flow into the burner. The solenoid
that controls the gas flow through the first chamber has
two coils: the booster coil and the holding coil. The
solenoid that controls the second chamber has one coil,
the secondary coil.
51
Booster
Secondary
Holding