Abstract: An arc welder with current and voltage control. The welder includes a current control loop for sensing and controlling the arc current. In an operating state, a voltage control loop senses an average arc voltage and controls it to be equal to a setpoint, by sending a current control signal to the current control loop, the current control signal being a constant frequency, variable duty cycle square wave. When starting a weld, the welder operates for an initial time interval in an arc-starting state, in which a constant frequency, constant duty cycle square wave is sent to the current control loop as a current control signal. In some embodiments the weld head position is controlled based on a ratio of the average arc voltage to the average arc current, and the frequency of the current control signal is adjusted to be synchronized with droplet detachment from the feed wire.