Why Does Inductive Kickback Voltage Vary in a Solenoid?

  • Context: Undergrad 
  • Thread starter Thread starter arul005
  • Start date Start date
  • Tags Tags
    Voltage
Click For Summary

Discussion Overview

The discussion focuses on the theoretical calculation of inductive kickback voltage in a solenoid, specifically examining why the observed voltage surges vary significantly during experiments. Participants explore the relationship between current change and induced voltage, as well as the limitations of their measurements.

Discussion Character

  • Technical explanation, Experimental/applied, Debate/contested

Main Points Raised

  • One participant requests help with calculating the inductive kickback voltage for a solenoid with given parameters, noting observed surges between 80-200V.
  • Another participant provides the formula for inductive emf, indicating that it depends on the rate of change of current, and suggests that the initial data provided is insufficient for a complete analysis.
  • A participant calculates the expected voltage surge based on a current change from 1A to 0A over 1 ms, arriving at a value of -8V, which contrasts with the higher observed surges.
  • Another participant suggests that the discrepancy arises from using an average rate of change rather than the instantaneous rate, proposing that the actual rate could be significantly higher at the moment of measurement.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the reasons for the varying voltage surges, with differing views on the adequacy of the calculations and the nature of the measurements taken.

Contextual Notes

Limitations include the potential inaccuracy of the measurement instruments and the assumption regarding the rate of current change, which may not account for instantaneous variations.

arul005
Messages
2
Reaction score
0
please help me with the theoretical calculation of inductive kick back voltage for a solenoid(supply voltage is 12V,L=8mH and current passing through is 1A)

i tried experimenting i got surges around 80-200V. why is it varying from time to time. please tell me a method to predict the exact surge without experimentation.
 
Physics news on Phys.org
The formula for the inductive emf is:

<br /> \mathcal{E} = -L \, \frac{d I}{d t}<br />

As you can see, it depend on the rate of change of the current in the circuit. Your data is insufficient to solve the problem.
 
current changes from 1A to 0A(in 1 ms) when i switch off the supply of 12 V


so according to the formula:


e=-(8*.001)*(1/.001)
=-8V

but the actual surge voltage is greater than 80V every time.
 
That's cause you estimated the rate with the average rate. The instantaneous rate of change might be 10 times higher at the instant when you read the voltage. Your instrument might be in a mode where it measures the peak signal.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 16 ·
Replies
16
Views
5K
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 12 ·
Replies
12
Views
6K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 9 ·
Replies
9
Views
3K
Replies
1
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K