Which of the following is NOT the advantage of lead compensator in a control system?

Lead Compensation:

• A system that has one pole and one dominating zero is known as a lead network.
• The basic requirement of the phase lead network is that all poles and zeros of the transfer function of the network must lie on (-)ve real axis interlacing each other with a zero located at the origin of the nearest origin.
• The figure shows below the electric circuit of the lead compensator.

The overall transfer function of the lead compensator is given below,

\(TF=\frac{1}{α}[\frac{1+α sT}{1+sT}]\)

Where,

\(α =\frac{R_1+R_2}{R_2}\)

and, \(T=\frac{R_1R_2}{R_1+R_2}\)

The pole zero plot for the above transfer function of a lead compensator can be drawn as,

Effect of Phase Lead Compensation:

• The velocity constant Kv increases.
• The slope of the magnitude plot reduces at the gain crossover frequency so that relative stability improves and error decrease due to error is directly proportional to the slope.
• Phase margin increases.
• The response becomes faster.

Advantages of Phase Lead Compensation:

• Due to the presence of a phase lead network, the speed of the system increases because it shifts gain crossover frequency to a higher value.
• It adds a positive phase to the system over the frequency range 1/αT to 1/T. Depending on the value of α, the maximum added phase can be up to 90 degrees.
• Due to the presence of phase lead compensation maximum overshoot of the system decreases.
• Because of new a dominant zero and a pole to the transfer function, the damping of the overall system become improved.

Disadvantages of Phase Lead Compensation:

• Steady-state error is not improved.