Mitsubishi Electric MELSEC iQ-R Series User Manual page 90

Heater disconnection correction function
When a heater voltage drops, a heater current is reduced. The R60TCTRT2TT2BW and R60TCRT4BW detect heater
disconnections by measuring a heater current. Thus, an accidental alert may be issued due to the voltage fluctuation caused
when a heater voltage drops.
The heater disconnection correction function corrects the amount of the heater current reduced (heater disconnection
correction), preventing the disconnections from being detected.
■Calculation formula for heater disconnection correction
Calculate (CH Heater current value) - (Reference heater current value). The largest positive value is used as the correction
value. When there is no positive value, the value with the smallest gap is the correction value. The heater current of each
channel is corrected using a correction value. When the corrected value is larger than the heater disconnection alert setting
value, a heater disconnection is detected.
Ex.
When "Heater disconnection alert setting" of "Heater disconnection detection setting" in "Application Setting" is 80% and the
differences between CH Heater current value and the reference heater current value are the following values:
• CH1: -2%
• CH2: 5%
• CH3: -1%
• CH4: -17%
The following table shows the result.
Channel Heater disconnection
alert setting
CH1 80 (%)
CH2
CH3
CH4
The correction value is 5%, and the heater disconnection detection judgment is executed on the following values: CH1: -7%,
CH2: 0%, CH3: -6%, and CH4: -22%. Because the heater disconnection alert setting has been set to 80%, a disconnection is
detected only in CH4.
Ex.
When "Heater disconnection alert setting" of "Heater disconnection detection setting" in "Application Setting" is 80% and the
differences between CH Heater current value and the reference heater current value are the following values:
• CH1: -16%
• CH2: -17%
• CH3: -22%
• CH4: -19%
The following table shows the result.
Channel Heater disconnection
alert setting
CH1 80 (%)
CH2
CH3
CH4
The correction value is -16%, and the heater disconnection detection judgment is executed on the following values: CH1: 0%,
CH2: -1%, CH3: -6%, and CH4: -3%. Because the heater disconnection alert setting has been set to 80%, none of the
channels are regarded as disconnected.
1 FUNCTIONS
88
1.27 Heater Disconnection Detection Function
Difference between CH
Heater current value and the
reference heater current
value
-2%
5%
-1%
-17%
Difference between CH
Heater current value and the
reference heater current
value
-16%
-17%
-22%
-19%
Corre Difference between CH
ction Heater current value and the
value reference heater current
value after correction
5% -7% (= -2% - 5%)
0% (= 5% - 5%)
-6% (= -1% - 5%)
-22% (= -17% - 5%)
Corre Difference between CH
ction Heater current value and the
value reference heater current
value after correction
-16% 0% (= -16% - (-16%))
-1% (= -17% - (-16%))
-6% (= -22% - (-16%))
-3% (= -19% - (-16%))
Disconnection
detection
None
None
None
Detected
Disconnection
detection
None
None
None
None