Mitsubishi Electric MELSEC Q Series User Manual page 51

3 SPECIFICATIONS
3 - 13
Downloaded from ManualsNet.com
(2) Heater disconnection compensation function
(a) Heater disconnection compensation
When the heater voltage drops, the heater current decreases as well.
The Q64TCTTBW, Q64TCRTBW heater disconnection detection measures
the heater current and determines the heater disconnection.
Therefore, when the heater voltage drops, there are possibilities that a false
alarm may be set due to the voltage change.
Therefore, the Q64TCTTBW, Q64TCRTBW compensates for a drop in heater
current (heater breakage compensation) so that the drop in heater current
does not activate the break detection.
(b) Heater disconnection compensation method
The heater disconnection compensation calculates "the heater current for
each channel" - "reference heater current value," and the largest positive
value is set as the compensation value.
When there is no positive values, the value with the smallest negative value is
used as the compensation value.
The heater current for each channel is compensated with the compensation
value and a heater disconnection is detected when the compensated value
exceeds the specified heater disconnection alert setting value.
Example 1: When the difference from the reference heater current value is:
Channel 1: -2%, Channel 2: 5%, Channel 3: -1%, Channel 4: -17%, the
compensation value becomes 5%.
The heater disconnection detection is performed from the values after a 5%
compensation: Channel 1: -7%, Channel 2: 0%, Channel 3: -6%, Channel 4:
-22%.
Thus, when the heater disconnection alert setting value is at 80%, only
channel 4 is detected as disconnected.
Heater
disconnection
Channel No.
detection setting
value
1
2
80%
3
4
Example 2: The difference from the reference heater current value is:
Channel 1: -16%, Channel 2: -17%, Channel 3: -22%, Channel 4: -19%, the
compensation value becomes -16%.
The heater disconnection detection is performed from the values after a -
16% compensation: Channel 1: 0%, Channel 2: -1%, Channel 3: -6%,
Channel 4: -3%.
Thus, when the heater disconnection alert setting value is at 80%, none of
the channels are detected as disconnected.
Heater
disconnection
Channel No.
detection setting
value
1
2
80%
3
4
search engine
Difference from the Compensation
standard current value
-2%
5%
5%
-1%
-17%
Difference from the Compensation
standard current value
-16%
-17%
-16%
-22%
-19%
MELSEC-Q
Difference from the
Disconnected
standard current
after compensation
-7% No
0% No
-6% No
-22% Yes
Difference from the
standard current Disconnected
after compensation
0 No
-1% No
-6% No
-3% No
3 - 13