How does a precharge circuit work?

A precharge 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. In some applications, such as industrial power supplies or utility power distribution, usage of a precharge circuit is infrequent.

How does a precharge resistor work?

A pre-charge resistor is a device that slowly charges the capacitors inside a electronic speed controller before it is powered up. Without this resistor, closing the contactor would generate a large amount of inrush current causing the contacts to arc. This arcing can permanently weld the contacts in the “on” position.

What is precharge capacitor?

The precharge resistor allows the capacitors in the controller to slowly charge BEFORE the contactor closes. This means that there is less voltage across the closing contacts and little or no inrush current.

What is precharge mode?

Pre-charge of the powerline voltages in a high voltage DC application is a preliminary mode which limits the inrush current during the power up procedure. A high-voltage system with a large capacitive load can be exposed to high electric current during initial turn-on.

What can you do with a precharge resistor?

If a precharge switch is added in series with the precharge resistor it can be used to turn the high Voltage on without switching a large current flow, as is done with the contactor or power switch. In this configuration the power switch becomes an emergency disconnect that is normally left on.

What are the components of a precharge circuit?

Precharge. The precharge circuit consists at the minimum of: A precharge resistor, to limit the inrush current (R1) A contactor (high power relay) across the precharge resistor (K2) to bypass the resistor during normal operation Additionally, the precharge circuit may have: A precharge relay…

How does a high voltage pre charge circuit work?

The functional requirement of the high voltage pre-charge circuit is to minimize the peak current out from the power source by slowing down the dV / dT of the input power voltage such that a new “pre-charge mode” is created. Of course the inductive loads on the distribution system must be switched off during the precharge mode.

When does a pre charge circuit return to normal mode?

Definition of a pre-charge function. Normal operation of a pre-charge circuit is to terminate pre-charge mode when the circuit voltage is 90% or 95% of the operating voltage. Upon completion of pre-charging, the pre-charge resistance is switched out of the power supply circuit and returns to a low impedance power source for normal mode.