Unox MINDMaps BAKERTOP, Service Manual

Page: 73 / 216

■ SCALE INVERSION parameter: the motor does
make the inversion, but on the basis of the current
cooking step duration, as reported in
table 15
.
table 15
Scale inversion parameter
Step duration Time base
< 16’ 100
<32’ 200
>32’ 300
For the inversion of the motor there are 3 seconds
of pause to allow the stabilization of the motor after
the activation of the triac on the power board.
Every 17 seconds the oven performs the humidity
and speed measurement.
Motor working status
The status of the ventilation is summarized in
Table 16 and described below.
table 16
Motor working status
Status Input Output features
Motor
inactive
period
Braking
step
No alarm
triggers
LP=0
Motor start
-up
Required
3” timer
ends
LP = max
Steady
state
Starting
ended
Humidity
measure-
ment
LP from
Table 2
Motor
has to
make the
inversion
17” timer
starts
Humidity
measure-
ment
17" standard
use timer
expired
6” timer
starts
LP
measurement
Braking
step
Inversion
requested
- -
Speed
change
requested
Motor inactive period
The motor does not spin if there is any alarm or
when the pulse mode is requested and the heating
elements are off.
Motor start up
If the ventilation is requested and pulse mode allows
it, the system is ready to start.
The inversion (100 seconds) and the stabilization (3
seconds) timers start up.
Steady state
Once the motor speed stabilizes after the required
3, the humidity measurement timer of 17” starts. The
humidity measurement takes 6”.
Braking step
The oven brakes when:
■ A motor revolution inversion is requested (every
100”)
■ A change of motor speed is requested or in pulse
mode (the fan slows down and stops if the pulse
mode is selected and the heating system is off).
The braking of the motor requires the inversion
of the polarization of the motor and the activation
of both the resistances, R1 and R2. If after 10
seconds the motor speed is greater than 200 RPM
or if the tachometer is damaged, the motor
switches off.
Humidity measurement
If the parameter HUMIDY MEASUREMENT is
set to ON, the humidity reading inside the
cooking chamber is if the following conditions are
met::
■ Every 20 seconds of working at standard use (not
during the washing program, preheating step and
fumes test);
■ If the motor is not in pulse mode;
■ If the temperature in the cooking chamber is 70˚C
(158 °F) ≤ Tch ≤ 200˚C (392 °F);
■ If the tachometer is working properly;
■ After the first 20 seconds from any change of the
motor speed.
Method applied for the humidity
measurement
The humidity measurement is a function of the air
density and temperature.
The humidity measurement is performed by
measuring the RPM of the motor with the
tachometer. At speed 4, if LP
measurement
≠ LP
standard use
, the
system considers the instantaneous speed of the
motor at the end of the 6 second stabilization period.
Otherwise, for the other speeds, the system considers
the average of the readings of the tachometer, v
m
,
along the same time frame (6”).
The output data are the motor speeds in saturated
and dry conditions, v
sat
and v
dry
calculated at T
ch
through a linearization of the data registered
during the humidity calibration in saturated and dry
conditions, speed data are collected at 100 °C (212 °
F), 120 °C (248 °F), 140 °C (284 °F) and 180 °C (356 °F')'.
If the humidity calibration has not been done, the
system works in an open loop system.
v
sat
and v
dry
registrered during the humidity calibration
are corrected according to the frequency and the
supply voltage.
Note for the first start: if the speed is set to 1,
the fan starts at speed 2 until the cooking
chamber reaches 90˚C (194°F).
finished
73