Current Limit Control of Chopper (CLC)

Current Limit Control of Chopper (CLC)

Q. Explain time ratio control and current limit control chopper method for speed control of d.c. series motor. State any four advantages of chopper based D.C. drive.

Q. Explain with waveforms the control techniques used for chopper control.

• In this strategy the chopper is turned on when the output current i₀ equals a preset value I₂. The chopper is kept on till i₀ increases to another preset value I₁.
• The chopper is turned off when i₀ equals I₁ and is kept off till the current i₀ decays to I₂. The current i₀ is thus limited to a maximum of I₁ and a minimum of I₂ as shown in Figure.
  
• The chopping frequency and the pulse width are dependent on the load parameters.
• The advantage of current limit control is that the ripple (I₁ - I₂), in the load current i₀ can be adjusted to a small, predetermined value for wide range of loads.