# Derive relation between time and current in motor protection device

1. ## Derive relation between time and current in motor protection device

Dear all,

I am trying to imperilment The IT - characteristic feature for motor protection device.There are 2C,5C,10C curve feature . can someone suggest me how it can be implemented in C code.

Is there any example code available.

https://www.l-3.com/private/ieee/Mot...Principles.pdf

Is there any equation for setting current and time . which i can easily used for implementation.

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2. ## Re: Derive relation between time and current in motor protection device

Is there any update on below request

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3. ## Re: Derive relation between time and current in motor protection device

if equation is not available , use lookup table with interpolation.

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4. ## Re: Derive relation between time and current in motor protection device

I find solution for IT characteristic. this sample example given here. need c code

assume Overload current = 10A(user defined setting)

Over load current trip time =10s(user defined setting)

if curve 2C is selected

calculation are as below The relay should turn on 30% over load trip time i.e 13A
Trip_Time over_current
10 10
9 10.3
8 10.6
7 10.9
6 11.2
5 11.5
4 11.8
3 12.1
2 12.4
1 12.7
0 13

in code if the Nominal current exceeds overload current these are trip timing for relay. The timing and current will change as per user defined setting. can some one guide me C code.

5. ## Re: Derive relation between time and current in motor protection device

make an array of 'time[] ' with index as "current*10" and initialise with your values.
from the given 'current' enter the array as 'index' , get the 'time ' value.

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6. ## Re: Derive relation between time and current in motor protection device

How do you determine the trip time for arbitrarily varying currents? Notice that the shown IT characteristic follows a simple I^2 t function.

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