Rockwell Automation 20A PowerFlex 70EC/700VC - Manual (Page 90)

86 PTC Motor Thermistor Input
PID Lower and Upper Limits/ Output Scaling
The output value produced by the PID is displayed as
±100% in [PI Output Meter].
[PI Lower Limit] and [PI Upper Limit] are set as a percentage. In exclusive or speed
trim mode, they scale the PID Output to a percentage of [Maximum Freq]. In torque
trim mode, they scale the PID Output as a percentage of rated motor torque.
Example
Set the PID lower and Upper limits to
±10% with Maximum Frequency set to 100 Hz. This will allow the
PID loop to adjust the output of the drive
±10 Hz.
[PI Upper Limit] must always be greater than [PI Lower Limit].
Once the drive has reached the programmed Lower and Upper PID limits, the integrator stops
integrating and no further “windup” is possible.
PID Output Gain
[PI Output Gain] allows additional scaling of the PID loop output.
Example
The application is a velocity controlled winder. As the roll builds up, the output gain can be reduced to
allow the dancer signal to be properly reacted to by the PID loop without changing tuning of the PID
loop.
PTC Motor
Thermistor Input A PTC (Positive Temperature Coefficient) device (also know as a motor thermistor)
embedded in the motor windings, can be monitored by the drive for motor thermal
protection.
Configuration and Operation
The PTC is connected to either the dedicated PTC input (PF700VC only) or Analog
input 1 along with a pull-up resistor of 3.32k ohms (see the specific product manual
for a connection diagram). Note: Analog Input 2 does not support this function.
For connection to analog input 1, the drive can be configured as follows to either
fault or alarm:
•
[Fault Config 1], parameter 238, Bit 7 = 1 (enabled)
•
[Alarm Config 1], parameter 259, Bit 11 = 1 = (enabled)
•
Fault and alarm message = “Motor Therm”
For connection to the dedicated PTC input (PF700VC only), the drive can be
configured as follows to either fault or alarm:
•
[Fault Config 1], parameter 238, Bit 13 = 1 (enabled)
•
[Alarm Config 1], parameter 259, Bit 18 = 1 = (enabled)
•
Fault and alarm message = “PTC HW”
Note: If the drive is configured for both alarm and fault, the alarm condition is
ignored.
Alarm Operation
An alarm will occur when the PTC resistance increases above 3230 ohms (5V DC),
but must decrease below 2153 ohms (4Vdc) for the alarm condition to clear.
70EC 700VC 700H
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