Shimaden PAC18 Series, Instruction Manual

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12-2. Heater break alarm function (optional)
The heater break alarm is a function whereby an alarm is given to let you know when the heater is broken.
The function is effective for preventing product defects and negative impact of insufficient power.
12-2-1. Operation overview
In ordinary operating conditions, measure the current value of the steady heater by key sequence ‘3-2. Setting of break judgment standard for heater break’
and use as standard value.
Input the reduction rate (heater break alarm point) of the current value for the standard value by key sequence ‘1-12. Heater break alarm current.’
When the current is below the preset value for at least 5 seconds, the heater is judged to be broken and the heater break alarm occurs.
When the alarm occurs, the alarm display of the LED on the far left displays

and control operation output continues as is.
Alarm output is canceled as soon as heater current recovers, and the

display in the alarm display of the LED digit on the left is canceled.
If self- hold is required, an external self-hold circuit must be constructed.
12-2-2. Setting method
1) Preparation before setting
Switch to

of key sequence ‘3-2. Setting of break judgment standard for heater break’ of manual operation screen. (The dot on the right flashes.)
The heater is powered with output near that of actual usage and the heater temperature is sufficiently stabilized.
(You should however make the load current at least 25% of the rated current.)
2) Heater current value setting
When heater temperature stabilizes, press

and load the heater current value (standard value). (The dot on the right stops flashing.)
3) Heater break alarm point setting (HB alarm trigger point setting)
Set current for heater break in the range of 0 – 100% by key sequence ‘1-12. Heater break alarm current.’
(Alarm however does not occur if heater break alarm current is set to 0%.)
Example 1: Detecting break for 1 of 5 heaters
Current percentage for 1 break is 4/5 x 100 = 80%; set to about 90% between that and 100% current when operating normally.
Example 2: If using 1 heater
Set to 50% between 0% current when broken and 100% when operating normally.
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3. Precautions when setting
1) When setting steady heater standard current value by key sequence ‘3-2. Setting of break judgment standard for heater break’, do so with device output
set to maximum within the output range actually used. If set outside the actually used output range or when output is small (load current is less than 25%
of the rated current), the effect of detection error grows large and could result in malfunction.
2) You should set the heater break alarm point low by key sequence ‘1-12. Heater break alarm current.’
Depending on the type of load, detection accuracy may drop and result in malfunction.
Even in the case of constant resistance heaters, resistance value may vary according to heater temperature in some cases.
In some cases, it may be difficult to differentiate between that resistance value variation and resistance value variation due to 1 of several heaters being
broken. If there are many heaters (5 or more), if you set lower than the calculation value (value between 1 break and when normal),
you may be able to detect break of 1 of several heaters, but this is effective for preventing malfunction of HB alarms.
3) Variable resistance heaters can be controlled applicable load, but Heater break alarm function can not be detected rightly in some cases because the
change of resistance value is too large.
With variable resistance heaters, current may become lower than the standard current value of the steady heater measured by key sequence ‘3-2. Setting
of break judgment standard for heater break’ during usage. If so, set the value lower than the drop in current percentage.
Example: Using 2 heaters. If heater resistance is large when starting and current when starting is 70% of the heater current for ordinary operation,
set lower than 70% of the current when it drops.
Because current when starting is 70% and 50% when 1 heater is broken, if you set to 60% between the two, detecting break 1 of 2 heaters is possible.
If using 3 similar heaters, you cannot accurately set to a value between when the current drops to 70% and when current drops to 67% when 1 heater
is broken. Detecting break of 1 of 3 heaters is therefore impossible.
4) In the case of light loads of less than 15% of the rated heater current, heater break may not be able to be detected.
With transformer loads, current detection accuracy may drop. If using with light load to prevent malfunction (30% of rating or less) or transformer load,
base the heater break alarm point setting on 50% by key sequence ‘1-12. Heater break alarm current.’
5) To avoid malfunction, heater break alarm is not activated when output phase angle is less than 15%.