○ In this work period we designed, built and tested an aditional protection circuit for the power inverter, and a level sensor circuit, which detects the "low" and "high" levels in the biodiesel generator's primary oil tank.
The job of the protection circuit is to save the inverter in case of a fault event, for example if the consumed power becomes higher than a previously set value (due to a short circuit in the output). The protection module automatically interrupts the power supply to the inverter, in such a case. Figure 1 presents the block diagram for the protection circuit and its working principle.

 

Figure 1. The block diagram for the protection circuit and its working principle.
 
Figure 2 presents the protection circuit board mounted on the chassis of the biodiesel generator.
Figure 2. The protection circuit board mounted on the generator's chassis.
 
○ The "level detecting circuit" senses the existance of the oil between the "LOW" and "HIGH" levels in the main oil tank. The generator's main control board uses the signal provided by the "level sensor circuit" to drive the oil recirculation pump as a function of those signals. The working principle for the "level sensor circuit" is presented in Figure 4 and Figure 3 shows the "level sensor" as it is mounted on the biodiesel generator chassis.
Figure 3. The oil level sensor mounted on the generator.
Figure 4. The working principle for the oil level sensor.