Making an inverter all by you can be definitely lot of fun. However if the results are not satisfactory can completely spoil the whole purpose of the project. Installing and configuring the various inverter parameter like the battery and the transformer to with the actual assembled circuit needs special care and attention for deriving optimal results from the assembly. The article broadly discusses how to calculate and match a battery and transformer wit the relevant circuit and also enlightens regarding the possible faults that might be encountered and the respective troubleshooting procedures.
The article enlightens the many newcomers with some of the important clues, which might be helpful while configuring an inverter circuit with the battery and the transformer, so that efficient and optimal results can be achieved.
Configuring Inverter Parameters
While making an inverter, two points must be broadly taken into account – the transformer must be rated twice the maximum load that is expected to be used with the inverter and the battery must be rated at 1/4 more than the transformer ratings.
For example, if the inverter is expected to work at 12 volts, with maximum loads of 200 watts, the transformer must be rated at least 500 watts, corresponding to 40 plus amperage, roughly (dividing 500 by 12), and the battery in turn must be rated at = ¼ multiplied by 40 = 10, therefore 40 + 10 = 50 AH (minimum).
After procuring all the necessary components as explained above, it would be important to get them checked for compatibility with one another.
Only the battery, which is one the most crucial member, hopefully will not require any prior checking, because the printed rating and the charged voltage conditions should be sufficient to prove its reliability. It is assumed here that the condition of the battery is good and it’s relatively new and “healthy.”
Next comes the transformer, which is another most important component of the inverter, surely needs a thorough technical assessment. It may be done as follows:
The rating of the transformer can be best checked in the reverse order, i.e. by connecting its higher voltage winding to the AC mains input and checking the opposite winding for the specified outputs.
If the current ratings of the lower voltage section are within the maximum limits of a regular multi-tester (DMM), then it may be checked by switching ON the above AC and connecting the meter (set at, say AC 20 Amp) across the relevant winding.
Hold the meter prods connected across the winding terminals for a couple of seconds to get the readings directly on the meter.
If the reading matches with the specified transformer current, or at least is close to it, means your transformer is OK. Lower readings would mean a bad or a wrongly rated transformer winding.
The assembled circuit broadly needs to be checked for proper oscillation outputs across the bases of the power transistors or the mosfets.
This may be done by connecting the circuit to the battery, but without including the transformer initially. The checking should be done using some good frequency meter or if possible using an oscilloscope.
If the above gadgets are not there with you, a crude testing can be performed using a pair of ordinary headphones. Connect the headphone jack to the bases of the relevant power transistors; you should get a strong humming sound in the headphones, confirming a sound functioning of the oscillator stages.
The above confirmations should be enough to prompt you to configure all the sections together.
Connect the transformer to the relevant transistor or the power devices terminals; make sure the power devices are correctly integrated with the oscillator stage.
Finally the battery may be connected to the power inputs of the above configuration, again do not forget to include an appropriately rated FUSE in series with the battery positive.
The output of the transformer now may be attached with the specified maximum load and the power may be switched ON.
If everything’s is wired up correctly, the load should start operating at its full fledged power, if not, then something’s wrong with the circuit stage.
Since the oscillator section was appropriately checked before the final installations, surely the fault may lie with the power device stage.
If the fault is associated with low power outputs, the base resistors may be tweaked for possible faults, or may be reduced by adding parallel resistors to their existing base resistors.
The results may be checked as discussed above, if the results are positive and if you find improvements in the power outputs, the resistors may be further modified as desired, until the expected power output is delivered.
However this may lead to further heating of the devices and due care must be observed to keep them under check by either including cooling fans or increasing the heatsink dimensions.
However if the fault is accompanied with blowing of the fuse would mean a definite short circuit somewhere in the power stage.
The problem may also indicate a wrongly connected power device, a blown-of power device due to a possible shorting between the power device’s output terminals or the any of the terminals that needs to be perfectly kept aloof of each other.
Having explained a few of the above possibilities while configuring an inverter optimally, a thorough knowledge regarding electronic becomes an absolute necessity from the part of the individual who may be involved with the construction, without which the proceeding with the project may somehow get jeopardized.
After the initial shock wore off, I put on my thinking cap to come up with a PIC-based solution to the problem. What was really needed was a display and a buzzer, to get my attention should the voltage fall outside a specified range. So my design criteria was set, a series of LEDs could indicate the voltage and a buzzer would also be used to warn of problems.
Make sure that you do not confuse the zener (ZD1) with the diode when you are installing them; the diode is the larger package of the two.