GE MN-ValVue-v2-8-IOM Manuel de service télécharger pdf (Page 610)

100

101

ValVue Digital Communications Software Ver. 2.80

610

GE Oil & Gas

Alarm Type

Determines whether the alarms will

absolute

deviation:



An absolute alarm appears when the process variable

not

between the low and high alarm

values.

 A

deviation alarm appears when the process variable differs from

the setpoint by more than the low and high alarm

values.

Controller Parameter List

The following parameters for the process controller can be changed whenever the process

controller is operating:

Proportional Gain (%) P is the ratio of proportional action (part of controller output) to error.

Integral Time (sec) Integral time or reset time, is the time constant of integral control.

Derivative Time (msec) Derivative time or rate time is the time constant of derivative control.

Derivative Gain Derivative gain is a parameter for derivative control. Typical range is

8 to 16.

Beta This is nonlinear gain factor, ranging from -9 to 9. When beta is 0, the

controller gain is linear. Otherwise the gain is the function of error.

The larger the beta, the smaller the gain for small error.

Setpoint Low and High

Limits

The setpoint is constrained to be between the low and high limits.

Both local and remote setpoints are limited. The limits are entered in

the same engineering units as the process variable.

Ratio Gain and Bias In ratio control, the setpoint and process variable can be in different

engineering units or on different scales. The relationship between the

setpoint in process variable units and the raw setpoint is given by:

Setpoint (in process variable units)=Ratio Gain x Setpoint + Ratio Bias.

The setpoint in process variable units is used in the PID calculation to

compute error.

Low and High Alarm Limits Defines when the alarm lights on the controller view are lit. If abso-

lute alarms are selected and the process variable is not between the

low and high alarm limit, the alarm light is on. If deviation alarms are

set and the difference between the setpoint and the process variable

is not between the low and high alarm limit, the alarm light is on. The

alarm limits are entered in the same units as the process variable.

Manual Reset Bias Only applies to P or PD control. It is the process controller output at a

typical operating steady state. If the controller outputs range from

30 to 50% at normal operation, the Manual Reset Bias should be set

at 40% in order to minimize steady state error.

Output Rate Limit Limits how fast the output can change. It is expressed as the percent

of full output range per second and can be between 1 and 200 per-

cent.

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GE MN-ValVue-v2-8-IOM Manuel de service Page 610

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