# I am running 10 kVA alternator from 10 hp motor and need some technical clarification

Here is my equipment:

• I am using solar controller to run motor which runs alternator which generates electricity and which is used for my house đźŹˇ requirements.
• 10 kVA single phase 220 V, 50 Hz @ 1500 rpm alternator, PF = 0.8.
• Motor used to run it 10 HP, 3-phase, 440 V, 50 Hz, 1440 rpm AC induction.
• Supply is used in running is solar panels of 9000 W with a controller.

I can change the value of frequency, voltage and current.

Now the frequency is set to 56 Hz, voltage to 540 V, current to 16 A and power to 9000 W in solar controller.
The motor usages 500 V, 56 Hz and around 14 A supply. Motor runs at 1600 rpm and having pulley of same size.

Alternator generation is 245 V.

Whenever the load increases more than 10 A on alternator the output voltage starts decreasing. In proportionately rpm and frequency of motor starts decreasing and it gradually decreases to a level of alternator output comes to 170 V which is when my voltage controller cuts the load from alternator and after cutting motor again runs at 56 Hz and 1600 rpm and alternator generates 245 V again. It will run a load below 10 A only after that the motor decreases its rpm, frequency and the output is decreased below unusable level of 170 V.

Please ignore if I didnâ€™t gave any more information and please ask I will give that. Please guide me what should I do for getting at least 20 A at voltage above 220 V.

• Please draw out a diagram with all the functional blocks from the solar panels themselves all the way to the final circuit that generates the 220 VAC at 50 Hz. Show boxes for each block and wires/arrows between them. Indicate power factors and frequencies as appropriate. Do note that $10\:\text{kW}$ of real, delivered power is 13.5 HP of used work. Commented Jul 21 at 6:43
• The most likely reason for all this is that your solar panels cannot supply 9000W at that level of sunshine. Those 9000W only apply if the sun shines on them at 0° angle. Commented Jul 21 at 7:11
• Most likely the load is greater than actual generated solar power, at which point your regulator fails. Measure solar panel voltage and current. Without MPPT and 1000 W/m^2 and panels cooled to 25 degrees C, they will not deliver the rated 9 kW. Commented Jul 21 at 9:35
• Why the detour DC -> 3-phase AC -> rotation -> AC? Commented Jul 21 at 10:30
• You mention the panels are parallel to the ground with the sun directly overhead. But thats not optimal, and impossible. You are some distance from the equator, I assume north. For optimum power your panels should be angled to the south such that at solar noon there is a right angle from the panel surface to the sun. If you stood a pen on the panel there would be no shadow. But that would only produce maximum possible output for about an hour without tracking the sun east-west. Also every conversion is a loss of efficiency. Make mains as close to the panels as possible, no motors and alts... Commented Jul 22 at 5:15

Whenever the load increases more than 10 A on alternator the output voltage starts decreasing.

Very common of small alternators. In fact, so common that most gasoline generators today are inverter generators since the small alternator is so poor.

There used to be a time when gasoline powered generators created alternating current directly. Today, most of them are inverter generators. They create high voltage DC (maybe using a 3-phase alternator and a diode bridge), which is converted to alternating current using a true sine wave inverter. The true sine wave inverter uses pulse width modulation at high frequency to create a voltage whose approximate value is the sine wave, and then LC filter modifies it to become very close to the desired sine wave.

Your setup is similar to a gasoline powered generator that creates alternating current directly, without an inverter, using an alternator. They are very poor, you can't expect the voltage to be what you want, the frequency to be what you want, and the voltage to be constant as a function of the load.

Small alternators create such poor alternating current they are no longer used directly. They are used to create 3-phase AC which is rectified to DC, which is then converted to a high quality AC using a true sine wave inverter.

Note that your setup already has an inverter. Solar power creates DC, and your motor is 3-phase AC, so you have to have a 3-phase inverter somewhere in your setup.

Use that inverter directly to create the AC directly for your house. Don't convert it to rotating motion and back to alternating current again. If you do so, you get low quality power and very low efficiency.

This is a 4-pole alternator, it should be more than capable of delivering 20A of current.
Probably even with somewhat decent waveform, depending on the amount of copper and iron used inside.

But, 20A for you with 0.8 pf also means 4 kW. And that may be unavailble on the prime mover.

The stalling problem then experienced is most likely a power limitation. Then the voltage regulator underspeed protection acts by reducing the voltage proportionally to the speed to prevent overexciting the field winding.

Some installations have an automatic load shedding plan in place or this.

What can you do to get 20A whithout the complementary kilowatts?
Use inductive load! Then little power is used due to the power factor being almost zero.

Do not try capacitive load, this is outside of the capability curve and will make the voltage rise uncontrollably