Quick Short-Circuit Calculator

This option enables you to estimate the short-circuit currents in a 3-phase radial system. To use the program : Motors are allowed for automatically, a motor short-circuit contribution being added at each transformer secondary busbar. The motor contribution is based on the size of the connected motor load. By default this is set to 50% of the transformer rating at 208V busbars and 100% at all other voltages. These assumed loadings can be changed by clicking the Settings button. If you wish to keep the new settings for future use click on Save.

If the short-circuit calculator is being used for Arc Flash Calculation purposes, it is recommended that the motor contributions should be set to zero. The high resistance of the arcing fault means that the motor short-circuit time constants will be very short, and the motor contributions will decay quickly.

The calculations are approximate and assume that X/R is the same for each circuit component.