Pre-Power verification of Inverter Based Welder:

The following steps should be performed:

1. Test the functionality of the Power Switch. Confirm that it has continuity in the ON position, and provides a disconnect (is open circuit) in the OFF position. Check all poles of the Switch.

2. If the Inverter is capable of operating at multiple input Voltages, confirm the functionality of any external voltage selection Switches.

3. When the Inverter is first powered up the Bus capacitors (Main filter capacitors) are pre-charged for several seconds. This is to limit the inrush current, as a capacitor appears as a short circuit to the incoming power supply (Mains input Supply) at time equal to zero. If this is not done, the Input Rectifier and Main Power Switch would have to supply infinite current during this time (an impossible situation that eventually results in component failure). A high wattage resistor limits this initial current. Confirm that this resistor is not open circuit, or degraded.

4. Visually inspect the Bus Capacitors. These are normally large Radial electrolytic Capacitors. Confirm that the cases are not distorted, and that they are sealed (not leaking electrolyte). Ensure that the Bus Capacitors are fully discharged. Measure the value of the capacitors using a Capacitance meter.

5. With a DVM (Digital Volt Meter) placed in the Diode position, confirm that the Mains input Rectifier, and Secondary output diodes are functional. The diodes should show a forward voltage drop of between 0.2 to 0.8V DC when the Anode is positive in respect to the Cathode. An Open circuit condition (displayed as OL on some DVM's) will be shown when the probes are reversed.