YASKAWA E7U, Programming Manual

Page: 82 / 176

Programming 76
The proper value of the branch resistance is approximated by the formula:
Where: (R
ptc@Tr
x 3) = The resistance value of the thermistor at either the alarm or fault level adjusted for three phase (three
thermistors in series, refer to typical PTC thermistor characteristic in Figure 56).
V
S
= The supply voltage (+15Vdc)
V
ptc@OH3
= The rated voltage for the over-temperature alarm or fault
Function: PI Differential
Setting: 16
Normal PI operation will adjust the Drive output in order to match the measured feedback value to a desired setpoint. When
PI is operated in the differential mode, however, the Drive output is adjusted in order to maintain a desired differential between
two feedback signals. Air handling unit return fan speed control in a “volume snatching” strategy for building pressure control
is an example.
When the A2 analog input is configured as a PI Differential (H3-09= “16: PI Differential”), the A1 analog input becomes the
other PI Differential input. The desired differential is set by parameter b5-07 (PI Differential Setpoint) and can be set so that
A2 is held less than A1 (b5-07 <0) or A2 is held greater than A1 (b5-07>0).
When PI Differential operation is chosen, the A1 feedback level can be monitored by U1-24 (PI Feedback) and the A2
feedback level can be monitored by U1-53 (PI Feedback2).
Function: Not Used
Setting: 1F
When H3-09= “1F: Not Used”, any signal applied to the A2 analog input will be ignored by the Drive.
Rbranch
=
( R
ptc@Tr
x3) x ( V
S
-V
ptc@OH 3
)
V
ptc@OH 3