Ask Me Help Desk - How to calculate the amount of energy generated by a generator

Hi, I want to know calculate the amount of energy generated by a generator I mean those electromagnetic induction generator.

I know there are some factor to cosider like the strength of the magnet and the speed of the rotation but what is the measurement for these factors and how to calculate the energy produce per round?

Energy (watt-hours) = power (Watts) * time (hrs)

Energy is commonly expressed in kWh which would make the units of Energy (kWh) = power (kW) ( time (h).

Energy produced depends on load, voltage and time and the phase relationship of voltage and current in an AC generator.

If there is no load, there is no Energy produced.

Quote:

Originally Posted by KeepItSimpleStupid

Energy (watt-hours) = power (Watts) * time (hrs)

Energy is commonly expressed in kWh which would make the units of Energy (kWh) = power (kW) ( time (h).

Energy produced depends on load, voltage and time and the phase relationship of voltage and current in an AC generator.

If there is no load, there is no Energy produced.

Hmm... what is the load? I know that E= Pt but how can we calculate the energy produce by the generator per revolution?

Actually I am talking about the magnetic field, and the size of the magnet as well as the metal. I want to know about what size and how much magnetic field can produce how much energy. Hope you get what I mean

I do not know much about electric stuff as it is quite confussing. There are a lot of term like current volt watt vlotage ampere power watt hour and so on and I am not really very sure with the term so if the term I use which is energy in this case is wrong then I hope you can correct me.

Next what is the different between ac and dc generator? Can the energy produce by an ac generator be transferred to a high capacity rechargeable battery?

Hope u can answer my question here and also one in the other thread:

https://www.askmehelpdesk.com/mechan...or-268120.html

I want to add some things to this thread as well:

Load is what the generator is attached to. A light bulb, a space heater, a motor etc.

Brush DC motors can be used as a generator with no modifications.
It uses a permanent magnet and a commutator to make the motor move. DC is the same kind of voltage that you see in a battery.

AC generators generate AC currert or current that has a sinusoidal output. Generally the magnetic field is changed by varying the stator current. Thus stator cuurent regulates voltage. RPM of the engine regulates frequency. Residual in the stator is designed such that the AC generator can start. The lack of permanent magnets reduces weight.

Alternators, which are now commonly used in cars, use the same technique, they generate 3 phase AC at a frequency dependent on engine rotation. All the phases are rectified and turned into DC. This answers you question concerning AC generators charging batteries.

In some portable generators, both AC and DC voltages are created with different windings.

Three phase motors allow rotation because of the relationship of the sine wave voltages for each phase. They are also more efficient than the induction motor.

A special case of the DC motor is a n phase brushless motor. N is usually >=3. There are sensors that sense the angular position of the motor, such that it can be determined when to energize each particular winding.

Each winding is generally supplied with a pulse width modulated signal that determines speed.

To see how this might work with a DC brushed motor. If one applied the full voltage at 10% of the time, The motor will run much slower, but would essentially have the same torque as the higher speed.

So, DC motors can be used as generators, motors and in vehicle applications when they are used as a generator they create dynamic braking.

AC generators are generally rated in kVA. DC generators in Watts. The reason why is VA, is because of the phase relationship and different voltage and current waveforms.
If the voltage and cuurent are sinusoidal and in phase then ohms law works.

If the voltages and currents are out of phase then the power formula is replaced by P= V*I*Cos(theta). Cos(0) =1 for resistive loads.

If the VI relationships are non-linear and not in phase, but periodic, you need true RMS meters to measure the voltage and currents.

If they are not periodic then Power is difficult to measure.

The magnetic field question is a physics question.

Design of a generator is probably more involved because transformer design is an involved art too. There is eddy current losses, copper losses, thermal losses, wire spacing losses etc.
The basic equations escape me, but I think they are in a physics text somewhere.

Again with the basic equations, try the physics forum. Maybe a question phrased as:

What are the governing equations that affect DC generator design. Research what you know.

I found this:

DC Generator Theory Summary

So if I want to transfer the energy generated by a generator to a rechargeable car battery,
I must use a.c generator or d.c generator?

In the end, the voltage must be DC or direct current to charge a battery. It also has to be higher than the terminal voltage of the battery. We typically use a 12 V battery in a car, but the electrical system is 13.8 volts and we call it 12.

Term: Diode = recitifier. A diode rectifies.

DC generators used to be found in cars like in 1955 or earlier. AC generators, called alternators were used later because they are lighter. Generators could keep a car running without the battery. The car alternator can not because it's not designed to be self-exciting.

AC is changed into pulsating DC with diodes. It effectively turns a waveform of the form y= A*sin(Omega*t) into y = abs(A*sin(omega*t)).

Filtering with a capacitor averages this waveform and creates DC. Combining each rectified phase of a typical 3 phase alternator also averages the voltage somewhat. This is enough to charge a battery.

With a car we use a lead-acid battery that can supply a large current for a short amount of time. They get damaged when discharged heavily.

A deep cycle battery can be discharged heavily, but cannot supply a large amount of current for a short time.

Deep cycle batteries are used say in trolling motors for boats.

Battery technology determines energy density and exactly how the battery needs to get charged.

What do you mean by a generator can keep a car running without battery? I thought a car is run by petrol?

True: The engine has an electrical system that in the simplest of cases (coil and points) creates a spark. It also has lights, etc.

Without the battery the electrical system discharges and the engine stops in a car with an alternator. In a car with a real generator, you can start the car and disconnect the battery and the engine will continue to run.

Are you saying auto ignition? I read from the internet saying that the spark is due to the solenoid reasoning. The part where it generate spark is the secondary part, because its voltage is higher so is generate spark am I right?
And yes about solenoid with a solenoid we can change a low voltage to a high voltage does it mean that by using a solenoid? We can transfer an amount of energy that is more than what a generator has generated into a battery? Because the voltage is higher in the secondary part

Just like pramary has 1 coil of wire by secondary has 1000 coil of wire so if the generator generate 1 watt of energy the battery can receive 1000 watt of energy

Again, simple case. Old cars. The primary is 12V. A capacitor discharges into the primary timed by points. There are many turns in the secondary, so 30-40 thousand volts are generated. It's developed across the gap in the spark plug and you get a spark.

Power transformers keep the power relationships constant in the primary and secondary. VpIp=VsIs. The voltage transformation is related to the number of turns, thus Np/Ns=Vp/Vs. They only work with AC voltage.

The generator's voltage is primarily dependent on the number of turns of wire in the generator.

Quote:

Originally Posted by realrvz

just like pramary has 1 coil of wire by secondary has 1000 coil of wire so if the generator generate 1 watt of energy the battery can receive 1000 watt of energy

No. Power is conserved. Voltage will change by a factor of 1000. Current will decreas by a factor of 1000. See above post.

Watt give u the energy to operate something and what does volt do?
Are u an engineer?

You have power and energy really confused. Let's see if I can help here:

You consume say 2000 calories in a day. This is likened the energy contained in a liter of petrol, but not exactly. You can spend it at varying rates during the day. When you are done you have consumed say 1900 calories and stored 100 away as fat.

When you expend this amount of Power, you might do it by walking, reading, writing and keeping your heart beating. If you spend 10 cal/hr keeping your heart beating then that 10 cal/hr is similar to watts (joule/s). It can be converted to watts.

If you expend 10 cal/hr over a 24 hour period then you have expended 240 cal/24 hrs. or X killo-Watt-Hours. In fact this unit can be converted to such.

Current is like the rate you can eat the same size chunk of pizza.
Say 1 cm^3/sec.

Voltage is like how fast you can shove it in your mouth.

Resistance is proportional to the diameter of your esopophogus/length of the espohogus.

Ohms law (V=IR, P=VI) governs these relationships. Energy = P(watts)/unit time

Gee, I've never done this analogy before.

Aside:

There is an article in the August 2008 issue of the magazine Circuit Cellar that describes building an open source design for a 3 phase Electric motor for vehicle applications.

Am I an Engineer? Well, I got the title of Electronics and Engineering Expert. I have taken college courses in a curriculum that encompased many engineering disiplines with a degree in Electronics Technology with a 4.0 GPA and a bachelor's degree in Engineering. It included electrical, mechanical. Fluid mechanics, structural, HVAC etc. I have designed, built, troubleshoot laboratory instrumentation and have machine shop skills.

wow awesome grade, since you are an engineer of many area I think u can answer me some of the question.
Can you give me a specific number on what size of the metal and magnet can produce how much energy when the metal cut the field? Hope u understand what I mean here

Next, I have read an electrical engineering book and came across this sentence "10 MW with 4 h of storage" they are referring to a battery storage

does is mean that this battery can give out 10 MW of energy per second for 4 hrs?

If this is so then the toal energy that this battery can store is it 10MW x 3600 x 4?

And do you know which battery has the biggest capacity?

Can anyone answer my question above?

I have some old texts on generators. I may have to find and look there.

Battery density:

Battery energy storage in various battery types

Was it 10mW or 10MW and it what context?

Battery capacity, even though it's expressed in units such as AMP-hours. It does not mean that all rate relationships hold. A 1 Amp-hour battery will not likely supply 1 Amp for 1 hour and .5 Amps for 2 hours. I think the drain is usually at 1/10 the capacity. The relationship is non-linear and battery chemistry dependent.

Is "MW with 4 h or storage"