The 3250 Series consists of part numbers 3250 （60V/20A/300W）, 3251 （150V/8A/300W）, and 3252 （300V/4A/300W）. These AC & DC electronic loads are suitable for endless DC, AC, or DC and AC power source testing purposes; for example, testing AC to DC power supplies, AC to DC voltage adapters, DC to DC power supplies, AC transformers, Intercom System ring generators. （See figures 1 through 5） 

This article will discuss AC operation, DC operation and other functions in detail. 

Figure 1 Example of AC & DC Power Supply Testing 

Figure 2 Example of DC & DC converter testing  

Figure 3 Example of DC & AC Inverter testing  

Figure 4 Example of Power Transformer testing 

Figure 5 Example of Power Transformer and Rectifier testing 

1. AC Operation  

Figure 6 AC Equivalent circuit of CC mode operation 

1.1.2 The constant current mode may be used for AC source load adjustment or source capacitance testing. These functions may be programmed via the GPIB, RS-232C interface. 

1.2 Constant Resistant Operation Mode  

Figure 8 AC Equivalent circuit of CR mode operation 

1.2.2 The constant resistance operation mode may be used for over current start testing or AC power start up. While it can also be used for testing load adjustment rates or power capacity the power source output voltage will decrease as the current increases. Voltage and current should be recorded at the same time in order to calculate the change rate, which is different from the constant current mode previously discussed as having a stable load current where it is only necessary to record the voltage for the change rate. 

1.2.3 There is no need to set these units in the constant current mode because the electronic load current wave form reference source is a voltage wave form. （Please see diagram