The post explains a simple electronic load controller or governor circuit which automatically regulates and controls the rotational speed of a hydro-electric generator system by adding or deducting an array of dummy loads. The procedure ensures a stabilized voltage and frequency output for the user. The idea was requested by Mr. Aponso
The Circuit Request:
Thanks for reply and I was out of country for two weeks. Thanks for info and timer circuit is working very fine now.
Case II , I need electronic Load Controller(ELC)My hydro power plant is 5 kw single phase 220V and 50Hz and need to control excess power using ELC. Please give reliable circuit for my requirement
The Circuit Design
If you are one of those lucky people who have a free flowing creek, river stream or even an active small water fall near your backyard, you can very well think of converting it into free electricity simply by installing a mini hydro generator in path of the water flow, and access free electricity for lifetime.
However the main problem with such systems is the speed of the generator which directly affects its voltage and frequency specs.
Here, the rotational speed of the generator depends on two factors, the power of the water flow and the load connected with the generator. If any of these alter, the speed of the generator too alters causing an equivalent decrease or increase in its output voltage and frequency.
As we all know that for many appliances are such as refrigerators, ACs, motors, drill machines, etc voltage and frequency can be crucial and may be directly related to their efficiency, thus any change in these parameters cannot be taken lightly.
In order to tackle the above situation so that the voltage and the frequency both are maintained within tolerable limits, an ELC or electronic load controller is normally employed with all hydro power systems.
Since controlling water flow cannot be a feasible option, controlling load in a calculated manner becomes the only way out for the above discussed issue.
This is in fact rather straightforward, it's all about employing a circuit which monitors the voltage of the generator and switches ON or OFF a few dummy loads which in turn control and compensate for the increase or decrease in the speed of the generator.
Two simple electronic load controller (ELC) circuits are discussed below (designed by me) which can be easily built at home and used for the proposed regulation of any mini hydro power station. Let's learn their operations with the following points:
ELC Circuit using IC LM3915
The first circuit which uses a couple of cascaded LM3914 or LM3915 ICs are basically configured as a 20 step voltage detector driver circuit.
A varying 0 to 2.5V DC input at its pin#5 produces an equivalent sequential response across the 20 outputs of the two ICs, starting from LED#1 to LED#20, meaning at 0.125V, the first LED lights up. while as the input reaches 2.5V, the 20th LED lights up (all LEDs lit up).
Anything in between results in toggling of the corresponding intermediate LED outputs.
Let's assume the generator to be with 220V/50Hz specs, means the lowering its speed would result in lowering of the specified voltage as well as the frequency, and vice versa.
In the proposed first ELC circuit, we reduce the 220V to the required low potential DC via a resistor divider network and feed pin#5 of the IC such that the first 10 LEDs (LED#1 and rest of the blue points) just illuminate.
Now these LED pinouts (from LED#2 to LED#20) are also attached with individual dummy loads via individual mosfet drivers, in addition to the domestic load.
The domestic useful loads are connected via a relay on LED#1 output.
In the above condition it assures that at 220V while all the domestic loads are in use, 9 additional dummy loads also illuminate, and compensate to produce the required 220V @50Hz.
Now suppose the speed of the generator tends to rise above the 220V mark, this would influence pin#5 of the IC which would correspondingly switch the LEDs marked with red dots (from LED#11 and upwards).
As these LEDs are switched ON, the corresponding dummy loads get added to the fray thereby squeezing the speed of the generator such that it gets restored to its normal specs, as this happens the dummy loads are again switched OFF in back sequence, this goes on self-adjusting such that the speed of the motor never exceeds the normal ratings.
Next, suppose the motor speed tends to decreases due to lower water flow power, LEDs marked with blue start shutting off sequentially (starting from LED#10 and downward), this reduces the dummy loads and in turn relieves the motor from excess load thereby restoring its speed toward the original point, in the process the loads tend to switch ON/OFF sequentially in order to maintain the exact recommended speed of the generator motor.
The dummy loads may be selected as per user preference, and conditional specs. An increment of 200 watts on each LED output would probably be most favorable.
The dummy loads must be resistive in nature, such as 200 watt incandescent lamps or heater coils.
ELC Circuit using PWM
The second option is rather very interesting and even more simpler. As can be seen in the given diagram, a couple of 555 ICs are used as a PWM generator which alters its mark/space ration in response to the correspondingly varying voltage level fed at pin#5 of IC2.
A well calculated high wattage dummy load is attached with a sole mosfet controller stage at pin#3 of IC#2.
As discussed in the above section, here too a lower sample DC voltage corresponding to 220V is applied at pin#5 of IC2 such that the dummy loads illuminations adjust with the domestic loads to hold the generator output within the 220V range.
Now suppose the rotational speed of the generator drifts towards the higher side, would create an equivalent rise in potential at pin#5 of IC2 which in turn would give rise to higher mark ratio to the mosfet, allowing it to conduct more current to the load.
With increase in the load current, the motor would find it harder to rotate thus settling down back to its original speed.
Exactly the opposite happens when the speed tends to drift toward lower levels, when the dummy load is weakened in order to pull up the speed of the motor to its normal specs.
A constant "tug-of-war" continues so that the speed of the motor never shifts too much from its required specifications.
The above ELC circuits can be used with all types of microhydro systems, watermill systems and also wind mill systems.