Watlow Power Series Rev H - Manual (Page 25)

F e a t u r e s , C h a p t e r 5 Wa t l o w P o w e r S e r i e s ■ 5 . 3
Soft Start
Soft start is a variation of phase angle control
executed on startup in which there is a gradual
increase in power until the final selected power out-
put is reached. If soft start is selected, the system
will execute the soft start sequence each time a zone
starts active control. This happens at power-on and
on recovery from an alarm such as “Line Loss.” The
soft start time is the time it takes to achieve 100 per-
cent power after a zone restart. The actual time may
be greater than the set time because of the resolu-
tion, but the actual time will never be less than the
set time. Rate = 100.0 ÷ time. The actual power
achieved is set by the temperature control input (see
Figure 5.3a and 5.4a).
NOTE: Soft start is intended to be used only for slowly
increasing power on the initial power request.
Soft start is available in single phase and 3 phase, 3-
leg models only.
Soft start is always used in systems with phase angle
control mode selected unless [soft] is set to [```0] .
Setup Page:
Adjustable Soft Start - On Power Up
• Enter the Setup Page by holding ± ¬ for 2 seconds.
• When the display reads [algo], press Î until[CTr1]
[`set]
[`set]
is displayed. Press ® until [``$0] is displayed.
[soft]
Use the У О keys to set the desired soft start time
in seconds.
NOTE: Repeat this procedure for each zone that you wish to
configure.
Figure 5.3a — Soft start.
Maximum Rate of Change
The maximum rate of change is used during normal
operation of a phase angle controlled system (after
a soft start sequence ends) to cause large changes in
requested power to be implemented gradually. The
maximum rate of change of the power is defined as
the percentage of power change allowed every 0.1 sec-
ond. This prevents a sudden increase or decrease in
current from one phase angle level to another level
from one cycle to the next into a nonlinear load that
could be damaged or blow a fuse.
Setup Page:
Adjustable Maximum Rate of Change On
Signal Change
• Enter the Setup Page holding ± ¬ for 2 seconds.
• When the display reads [algo], press Î until [CTr1]
[`set]
[`set]
is displayed. Press ® until [`1)0] is displayed.
[rate]
Use the У О keys to set the desired % output
change per 0.1 seconds to reach the desired out-
put power level when in phase angle control.
Example:
Time needed for 100% change in power at selected [rate] :
10.0% increase = 1 sec. from 0 to 100% power
10.0% increase = 0.8 sec. from 10 to 90% power
10.0% increase = 0.4 sec. from 10 to 50% power
NOTE: The default for Maximum Rate of Change is set to
10%/0.1 second.
NOTE: Repeat this procedure for each zone that you wish to
configure.
Figure 5.3b — Maximum rate of change set to 10%.
Requested power level changed from 10% to 50% at (time) t1.
Actual power out has changed from 10% to 50% by t2.
Rate of change
limited by phase
angle maximum
rate of change.
100%
50%
10%
0%
t1 t2
0.4
seconds