When does Proportional (p.) Integral (I) Derivative (D) Controllers are Used ?

**When Proportional § Controller is Used during the following conditions:**

- Load Changes are small
- Offset (error exist due to difference between steady state value and desired value) can be tolerated
- The process reaction rate is such as to permit a narrow proportional band. Since this reduces the amount of the offset

**When Integral (I) Controller is Used during:**

- When the offset must be eliminated
- Integral saturation due to sustained deviation is not objectionable

**When Derivative (D) Controller is used:**

- Large transfer or distance velocity lags are present
- It is necessary to minimize the amount of deviation caused by the system changes

**When Proportional plus Integral (PI) Controller is used when:**

- System changes is small
- Offset must be eliminated
- No objection on the recovery duration

**When Proportional and Derivative (PD) controller is used:**

- When the system changes are small
- Improve the recovery time
- When system lags are high

**When Proportional, Integral and Derivative (PID) Controller is used when :**

- System changes are small
- Offset must be eliminated
- Fast recovery time