GaneshSS

16-11-2014, 05:24 AM

Hello we procured a iPro Genius controller with programming for AHU control - temperature, RH and blower speed control through VFD.

The tool offers a PID function block, but no explanation of the individual parameters. The parameters are as below. I am giving the same from the block description, as I am not very familiar with the versions of the tool itself.

Arguments:

Inputs:

INP Ingresso DINT Value of analog input (decimal °C)

SET Set DINT Set-point (decimal °C)

PB Pid_PB DINT Proportional band (decimal °C)

RS Pid_RS DINT Band offset (decimal °C)

INC Pid_INC DINT Sampling time of integral (seconds)

DER Pid_DER DINT Sampling time of derivative (seconds)

DDER Pid_DDER DINT Derivative time (seconds)

RST Reset Integrale BOOL If TRUE, the integral is reset

Outputs:

OUT PId_Out DINT Variable value (%) of control

STT STT DINT 0 = OK, else parameters not consistent

Description:

Pid regulator.

I am having problems with the VFD control part. The control is based on the differential pressure across the blower measured in Pascals - provided by a DP transmitter 0-3000 Pascals from Siemens. If the DP increases, speed has to reduce, if DP reduces, speed has to increase. The VFD gets a DC voltage 0-10V to effect this change. The VFD has already been programmed with minimum and maximum frequencies corresponding to 0V DC and 10V DC control voltage. I know I have to tune the parameters, but need to know the meaning of each parameter before attempting that. I have done some tuning of the temperature and RH loop and they seem to be working properly. As temperature increases/decreases, we open the chilled water more/less (again with 0-10VDC voltage to the actuator controlling a 3 way mixing valve at the outlet). As RH increases/decreases, we open the hot water valve more/less just as described above.

Can anyone help? I am not finding necessary help in India.

The tool offers a PID function block, but no explanation of the individual parameters. The parameters are as below. I am giving the same from the block description, as I am not very familiar with the versions of the tool itself.

Arguments:

Inputs:

INP Ingresso DINT Value of analog input (decimal °C)

SET Set DINT Set-point (decimal °C)

PB Pid_PB DINT Proportional band (decimal °C)

RS Pid_RS DINT Band offset (decimal °C)

INC Pid_INC DINT Sampling time of integral (seconds)

DER Pid_DER DINT Sampling time of derivative (seconds)

DDER Pid_DDER DINT Derivative time (seconds)

RST Reset Integrale BOOL If TRUE, the integral is reset

Outputs:

OUT PId_Out DINT Variable value (%) of control

STT STT DINT 0 = OK, else parameters not consistent

Description:

Pid regulator.

I am having problems with the VFD control part. The control is based on the differential pressure across the blower measured in Pascals - provided by a DP transmitter 0-3000 Pascals from Siemens. If the DP increases, speed has to reduce, if DP reduces, speed has to increase. The VFD gets a DC voltage 0-10V to effect this change. The VFD has already been programmed with minimum and maximum frequencies corresponding to 0V DC and 10V DC control voltage. I know I have to tune the parameters, but need to know the meaning of each parameter before attempting that. I have done some tuning of the temperature and RH loop and they seem to be working properly. As temperature increases/decreases, we open the chilled water more/less (again with 0-10VDC voltage to the actuator controlling a 3 way mixing valve at the outlet). As RH increases/decreases, we open the hot water valve more/less just as described above.

Can anyone help? I am not finding necessary help in India.