AB PowerFlex 750Series AC frequency converter Single-phase output

 Single phase output:

Consult Rockwell Automation before configuring the inverter for a single phase adjustable voltage output. The frequency converter must be derated due to the stress on the DC bus capacitor or the loss of the IGBT switch. When PWM is applied to the resistor, the current state will change with the voltage. For each PWM voltage pulse, the current is pulsed in the same way. This rapid current change is not suitable for IGBT selection of inverter. A degree of derating is therefore required. The reduction is about 67 percent. In this mode, the actual loss must be measured to determine the derating percentage.

A reactor in series for the resistance can help by increasing the inductance and smoothing out the Angle of the current pulse. Depending on the size of the increased inductance, the waveform may be close to a sine wave.

The figure below shows the output voltage, output current, and DC bus voltage. This diagram shows that the current varies with voltage in a typical PWM output.

Note the mutation at the top. The smoothing effect at the top of the waveform depends on the type of resistance used. The resistor used in this figure is a grid type resistor, and the resistance element is wound along its length to increase the inductance of a certain amount. The inductance helps smooth the rising edge of the current.

The following figure shows the waveform after a reactor is connected in series. These waveforms are similar to sine waves and are a function of the increased inductance. But the increased pressure drop must be taken into account.

Another solution is to add a sine-wave filter to the circuit. This makes it possible to use unshielded cables without worrying about noise from PWM entering the device. Among other factors, the cost of shielding the cable must be weighed against the sine-wave filter.

When using single-phase operation, the load is connected to the U phase and the V phase. W is connected to electricity, but not used.

Enter the maximum current in the Motor NP Amps parameter. The Current Limit parameter also uses this value. After the inverter is started, it will attempt to ramp up to the given voltage. If the current limit is reached, the inverter will maintain or reduce the voltage to meet the current limit.