In a 110 V DC chopper drive using the CLC scheme, the maximum possible value of the accelerating current is 300 A. The lower limit of the current pulsation is 140 A. What is the maximum limit of current pulsation?
In a 110 V DC chopper drive using the CLC scheme, the maximum possible value of the accelerating current is 300 A. The lower limit of the current pulsation is 140 A. What is the maximum limit of current pulsation? Correct Answer 440 A
Current Limit Control of Chopper (CLC):
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.
[ alt="F1 Nakshatra Madhuri 15.12.2021 D2" src="//storage.googleapis.com/tb-img/production/21/12/F1_Nakshatra_Madhuri_15.12.2021_D2.png" style="height: 350px; width: 439px;">
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 a wide range of loads.
Application:
Given,
The maximum possible value of the accelerating current (I2) = 300 A
Current pulsation or current ripple (ΔI) = 140 A
The waveform can be drawn as,
[ alt="F1 Nakshatra Madhuri 15.12.2021 D3" src="//storage.googleapis.com/tb-img/production/21/12/F1_Nakshatra_Madhuri_15.12.2021_D3.png" style="width: 487px; height: 152px;">
From the waveform,
The maximum limit of current pulsation (I2) = I1 + ΔI = 300 + 140 = 440 A
