Lead Compensator Vs Lag Compensator | Difference between Lead Compensator and Lag Compensator

This page compares Lead Compensator Vs Lag Compensator and mentions difference between Lead Compensator and Lag Compensator. The circuit diagrams for Lead Compensator and Lag Compensator along with transfer functions are also mentioned.

Definition:
The compensator is a device used to improve performance specifications such as steady state and transient responses.

Lead Compensator

Lead Compensator

The figure-1 depicts circuit and transfer functions of Lead Compensator. It is similar to PD controller. Following are the features of Lead Compensator.
• Here zero is closer to origin than the pole.
• It improves transient response.
• It increases the bandwidth.
• (S/N)output < (S/N)input
• It helps to increase error constant upto some extent.
• It allows to pass higher frequencies and attenuates lower frequencies.
• Increases phase shift.

Lag Compensator

Lag Compensator

The figure-2 depicts circuit and transfer functions of Lag Compensator. It is similar to PI controller. Following are the features of Lag Compensator.
• Here pole is closer to origin than the zero.
• It improves the steady state response.
• It increases error constant.
• It decreases bandwidth.
• It reduces effect of noise.
• It reduces stability margin.
• It does not affect the transient response.
• System becomes lesser stable.
• It allows to pass lower frequencies and attenuates higher frequencies.
• It decreases the phase shift.



Lead Lag Compensator

Lead-Lag Compensator

The figure-3 depicts circuit and transfer functions of Lead-Lag Compensator. Following are the features of Lead-Lag Compensator.
• It improves both steady state and transient responses of the system.

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