Low Pass Filter Design: Choosing L & C for Cut-off Frequency of 50Hz

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SUMMARY

The discussion focuses on designing an LC low pass filter for a single-phase sinusoidal PWM inverter with a cut-off frequency of 50 Hz. The formula for determining the cut-off frequency is given as f = 1/2π√(LC), indicating that multiple combinations of inductance (L) and capacitance (C) can achieve this frequency. Participants emphasize the importance of considering the load across the capacitor (C) and suggest designing the circuit as an LCR arrangement to account for the load's resistance (R). Mathematical analysis and frequency response graphing are recommended for evaluating the filter's performance.

PREREQUISITES
  • Understanding of LC circuit theory
  • Familiarity with the formula for cut-off frequency f = 1/2π√(LC)
  • Basic knowledge of single-phase PWM inverter operation
  • Ability to analyze frequency response graphs
NEXT STEPS
  • Research methods for calculating inductance (L) and capacitance (C) values for desired cut-off frequencies
  • Explore LCR circuit design principles and their impact on filtering performance
  • Learn about load modeling in LC circuits and its effects on filter behavior
  • Study frequency response analysis techniques for evaluating filter designs
USEFUL FOR

Electrical engineers, circuit designers, and hobbyists involved in designing low pass filters for PWM inverters or similar applications will benefit from this discussion.

hisham.i
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Hello,

I am designing LC low pass filter for single phase sinusoidal pwm inverter, where the cut off frequency is f = 50 Hz.

And i have to chosse L, C such that: f = 1/2π√(LC)
but there is many combinations of L and c that result in this cut off frequency.

So my question is, how to choose these values?
 
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A load is going to appear across C? This may have a major effect on the filtering ability of your L-C arrangement. You need to design it as an LCR circuit from the start, assuming you can represent your load as R.

Apply some maths, and sketch frequency response graphs, you'll see how it behaves.
 
hisham.i said:
Hello,

I am designing LC low pass filter for single phase sinusoidal pwm inverter, where the cut off frequency is f = 50 Hz.

And i have to chosse L, C such that: f = 1/2π√(LC)
but there is many combinations of L and c that result in this cut off frequency.

So my question is, how to choose these values?

Do you need to select real parts, or is it just values that you need to select?
 

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