Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 120)

Publication 900-UM007D-EN-E - January 2011
3-50 Configuration & Basic Operation
3. For V connecting power lines: Refer to the following diagram for CT
installation positions.
Note: Heater voltage fluctuations are not considered here. Take this into
account when setting the detection current.
Figure 3.98 — CT Installation Positions, V Connecting Power Lines
How to Calculate Heater Current Detection Values
• Calculate the heater current value to be configured by using the
following equation:
• To calculate the current for heater burnout when two or more heaters
are connected through the CT, use the heater current value when the
heater with the smallest current burns out. If all of the heaters have the
same current, use the value when any one of them burns out.
• Make sure that the following conditions are satisfied:
– When using a heater with a normal load current of less than 10.0 A:
(Current value at normal operation)
− (Current value at heater
burnout)
≥ 1 A
When the difference is less than 1 A, detection is unstable.
– When using a heater with a normal load current of 10.0 A or more:
(Current value at normal operation)
− (Current value at heater
burnout)
≥ 2.5 A
When the difference is less than 2.5 A, detection is unstable.
CT
CT
Load
Load
Load (such as a heater)
AC line
To controller CT input
To controller CT input
Heater Burnout Detection 1/2 set value = Normal current value + Burnout current value
2
HS Alarm 1/2 set value =
Leakage current value (output OFF) + HS current value
2
Heater overcurrent 1/2 set value = Normal current value + Overcurrent value
2