T-I Graphing Calculator
Calculate operating time and plot the Time-Current characteristic curve.
Operating Time (t):
Understanding Time-Current Curves
A Time-Current (T-I) curve is essential in electrical engineering for protection coordination. It illustrates the relationship between the current flowing through a protective device (like a fuse or circuit breaker) and the time it takes for that device to trip or operate.
The Mathematical Model
This calculator uses a standard power-law equation often found in IEC standards for fuse characteristics:
t = K × (In / I)α
Where:
- t is the operating time in seconds.
- K is a time constant specific to the device.
- In is the rated current of the device.
- I is the prospective fault current.
- α is the curve exponent (slope).
How to Use This Tool
Enter the device's rated current and the specific constants (K and α) found in the manufacturer's datasheet. Then, input the fault current to see exactly how fast the device will react. The graph visualizes the characteristic curve, marking your specific fault point.