A high voltage system with capacitance on the output can be exposed to damaging inrush current when the system is first turned on. If this current is not limited and controlled, it can cause significant stress or damage to other components in the system. For example, welded contacts are one of the most common failure modes of mechanical contactors. A pre-charge circuit is used to limit this inrush current to slowly charge the downstream capacitance. It plays a critical role in the proper operation and protection of components in high voltage applications. Pre-charging increases the lifespan of electric components and the reliability of the system as a whole. A pre-charge circuit allows the current to flow in a controlled manner until the voltage level rises to very near the source voltage before the main contactors are permitted to close. The graph shows an example of the inrush current without a pre-charge circuit. Depending on the system voltage, pre-charge can take as little as a few milliseconds.