Generator Loads and Output Voltages

Generation becomes like any other motor when the power source diminishes. The phasors reverse, the generator stays in sync but the power source is now the grid.

Once the water or wind or steam returns, then the phasors reverse direction and power flows back into the grid.

The frequency balance is never off while the generator is hooked into the grid.

If it is running on no load !!! why to run it at all (ifl a load is drawn from the grid then all the gens will contribute to it on no load means there is no load on the grid ? ideal situation) and that means it is a homework question.

Pl go and study the portion of Sync gen in your text book (You may find a bit in the design of machines too if I remember)

Offtopic portion: (Pstt Euro not again)

getting bored of too many homeworks . hey didn't solve so many in all of my 5 years of engg (yes ot was five year then now since kids are aging faster it is reduced to 4 years proportional to life expectancy).

This is an interesting topic that I have thought about for some time. I would like to pose a similar question that may help in answering this one. I have multiple small generators from 3kw to 10kw. I have a need occasionally at a bible camp, (it is in a remote location and susceptible to frequent power outages) to run the camp on generated power. We currently set up a generator for the well pump and one for the kitchen ( refrigeration) and bath house (for obvious reasons). Can the generators be synchronized to run more together than just the one area? i.e. additional lighting, fans, and the pool circulating pump. Both generators are rated for more than is currently being used but in order to run these additional items, the main panel would have to be fed thus opening up a myriad of possible power consumption. I currently have an automatic disconnect that will isolate the power grid that is approved by the power company. If I can sinc multiple gen sets, (of different kw ratings) then I could add the needed power to run all of the camp. If anyone has ideas please reply.

Yse you can, only you need a few things like governor etc, the total equipments with the automatic controls etc may fill up approximately one small sized room (obviously you need an AC to keep the temperature of room down) and the operation and control expert who will keep on looking at the alarms and adjust a knob here and there.

The alternative is to have the total control to be housed inside an AC van and bring to the camp along with the operations man (not chap you know, there is no depression in this sector)

The next alternative is get a larger generator (and thereby saving energy)

SB,

Thanks for the reply. My train of thought would lead me to believe that once the gen sets are in sinc they will remain in sinc. I believe this to be for the reasons stated in the second reply to this thread. If the grid (at this time the multiple gen sets) are in sinc then as the total load is increased then each set will supply its % of increase thus remaining in sinc. If a sudden load in incurred, i.e. compressor startup, then they will all be loaded to the proportion of rated output and then remain in sinc. If one tries to accelerate or decelerate, then the others will maintain it in sinc as it will try to "motor" from the grid. Is this true.

Bear in mind that your small 3-10 KW generators may be induction tyope and not sybchronous type.

You will need synchroscope and interconnecting power cables sized to carry the maximum load.

Your circuit breaker s will have to be able to trip quickly to avoid damage in the event of a fault.....

Stuff we do in a power plant...

Generators can be paralleled by making an equalizer connection to prevent one of the generators from acting as a motor running off the other generator. An equalizer is a connection between the series fields of the two gensets. This will maintain the same voltage across all series fields. The connection needs to made on the armature end of the series fields to the same polarity on both generators. Paralleling multiple small generators is not practical. One large generator is a better solution, but then the problem of the distribution wiring for the whole camp.

I agree with this reply from the question. It is practical to use 1 generator with the specified output power needed.

Anyway, what is the purpose of connecting mulitple generators in parallel?

To increase fuel efficiency and reduce consumption? Well, we have to think more than that.

Currently, I am working (R&D) on a power generator that consumes minimal power source but produces substantial greater power output.

cheers!

While the answers that were sent to you do not sound like there is a practical solution, there is always the thought of trying to collect some alternative power solutions.

Is there an abundance of wind? Convert an old belt drive ventilation fan to collect this power, and turn it into 12 volts with salvaged automotive batteries, and alternators. Just replace the belt drive fan motor with automotive alternators. Feed the power to salvaged automotive batteries. 12 volt lighting with LEDs is very efficient. If you can find an inverter of sufficient power to run your refrigerator(s), they could also be connected to your battery-wind farm.

A good project while at camp.

let me explain to you the no-load SB.if you close the circuit breaker of the Generator and make it parallele with the grid, and you dont excite the shaft of it with any source like water, steam whatever, it is the no-load situ. I think you need some book-searching all the same, i hope u will get better information there...

I Mean you dont let extra amount of water or steam to the shaft and take any load from grid, i think Jinxnao is right, u wont get loaded without excite the shaft....

Connecting multiple 1 to 5 KW or so generators is going to be very difficult and require control changes that will make the project prohibitively expensive UNLESS you have Honda inverter type generators which are designed to be connected in parallel.

The Honda series in the link below and perhaps a few others are capable of this parallel connection feature. For an explanation see here: http://www.hondapowerequipment.com/products/generators/content.aspx?asset=gg_parallelcapability

This capability allows connection of two of the same type of generators in a network you construct to share load and maintain frequency. These generators are also much more fuel efficient than the common run of the mill Coleman, Troy-built, YouNameIt brand of gasoline, NG, Propane or diesel generators.

The most common result of connecting small generators (actually alternators) in parallel is that the voltage and frequency (speed) swing violently resulting in tripping or damage to one or both of the machines and perhaps the load equipment. If the engines have droop type governors and droop type automatic voltage regulators, some times they may actually parallel and share. Usually though, one takes or tries to take all of the load and the other slacks off and does nothing.

It the example of the first post, what happens if the energy source to the prime mover is lost, Well, one of two things happen. The generator trips off on reverse power protection or the machine continues to run at synchronous speed. If it is allowed to run at sync. speed then some power factor correction may be gained by adjusting the excitation to generate reactance to correct the power factor if needed.

Have FUN!
TT3

Jinxnao,

If you reduce the input power (shaft) but keep the exciter power the same, the generator continues to act as a generator but with a different power factor, since both voltage and frequency are imposed by the grid it generates to. The reactive power remains quasi at the same level, while the active (real) power drops.

The input power (mechanical) accounts for the active (real) output power component and also for losses (windings, mechanical, etc) inside the machine. If the excitation power is taken from the generator (self-excitation), this also adds to the real power requirements.

When reaching a minimum level of power input, when the input power no longer is able to cover the losses inside the machine, the machine changes its characteristics from a synchronous generator to a synchronous motor (it starts turning the turbine/driving engine). The power factor of that synchronous motor is again dependent on the level of excitation power. The voltage and frequency are set by the grid.

There is another consideration if the prime mover is a steam turbine. If the steam is cut off to the driving turbine, there will be no steam flow through the turbine and the windage losses from the rotor fanning the trapped steam will gradually heat up the machine until it gets so hot the rotor, housing and bearings are damaged. This is why steam turbines connected into a multiple machine network or to the grid always have reverse power protection.

I have seen both induction and synchronous types of turbines glowing from the heat of the trapped steam heated by the windage losses. More than a few machines have been damaged or destroyed this way.

Happy New Year!
TT3

hii. İ GOT MY ANSWER FROM MY SEARCHİNGS. all my friends missed the point but only tomad got near it:) thr answer is while my generator is operation on no load and coupled to the grid if i reduce my driving power it will act as if it was a motor. İn fact tomad just overexplained it:) THank you all....

Seems that you didn't read post #1? I tried for simple, same answer. Ah well, glad you got what you needed.

ah you are right excuse me...