Switching generator sets

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ssembo

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I want to design a circuit that will have to switch two generator sets at 415V of 5kW and 10kW with the combination producing power of either 5,10, or 15kW depending on the need.

I am planning to determine the need by sensing the current drawn by the loads using a current transformer. The circuit will have to compare the load current and effect the production of the required power.

What can i use to have the three options i talked of when and only when needed?

Thanks

Colin
 
Since you plan on using a current transformer I assume this is AC current. So how will you synchronize the phase between the two generators, which is required if you connect them together?
 
syncronising

ssembo, that link is very interesting.

In my experience I prefer the 3 light method, if you have no synchronouscope.

By cross phasing two lamps you can switch with one light dark and two equally bright and close the switch.

The lamps have to be rated at twice the voltage and should be of clear glass.

When out of synch the lamps go on and off after each other, when the generators are nearly at the same speed the lamps slowly go, off, dim, bright, dim and off.

Major damage will occur when generators are out of synch. and the parrallel switch is closed.
 
As well as the lamp, you might also connect a multimeter set to measure AC between the two generators. That way you can more precisely determine when the voltage between the two phases is at zero.
 
Great ideas.

By the way i am planning to do this as my final year project. Need to convice the world that its viable.

Secondly, need to know how am to do this. Some people have suggested the use of microcontrollers "b bit 18F family" to do the logic. Whats the best way of determining load demand?
 
Two things, Only use two generators that are the same.
you need a fail safe system to disconect them is on stops. Andy

 
ssembo said:
Secondly, need to know how am to do this. Some people have suggested the use of microcontrollers "b bit 18F family" to do the logic. Whats the best way of determining load demand?
Click to expand...
If you are planning on doing this switch-over automatically then you would certainly want to use a micro.

Your suggestion of using a current transformer for measuring the load current is a good way. An alternate would be a hall sensor but that tends to be more complicated.
 

If i happen to use self starting generators and my circuit is just to give them a signal to either start or go off, will they still run in sysnchronism? What i mean is: if i carry out the procedure of synchronism discused, and say at one moment, one generator is on and the other has to come in, will they still be run in synchronism?

Thanks
 

Have used a current transformer before and made 4 turns through a current transducer to get a range of 4-20mA which i passed accross a 500ohm resistor and got a voltage range of 2-10V. Guess thats enough information to help me here.

My issue is now how i can connect it to my microcontroller? Help me out

Thanks
 

No you can not start or stop them when thay are still tyed together. You will need a sequnce to do this.

1 start gen #1
2 start gen #2
3 synchronize then
4 tye them to gether
5 monitor them
6 If one stops, disconect them
7 disconect them
8 stop them

Andy
 

I am designing an automatic circuit...from your view it means that i have to have a design that will have to synchronise the two every time they are both to be on? If say the 5kW generator is on and the 10kW generator has to come in inorder to have the 15kW system, i mean i will have to start the 10kW, synchronise it and then be able to connect them together? If thats the case, any ideas of what can do the synchronisation automatically?

Thanks
 
i mean i will have to start the 10kW, synchronise it and then be able to connect them together? If thats the case, any ideas of what can do the synchronisation automatically?
Click to expand...
From the link you provided in post #3 thats what you have to do, just how I do not know. Andy
 
Certainly any time two genenerators are powered up they, will not have the same exact frequency or phase, even if they were previously phase locked.

Doing this automatically would appear to be a difficult problem. You would need a micro programmed with a control loop to detect the difference in frequency between the two generators, adjust the speed of one until they are in phase, then close the relay to connect them together.

Making the control loop stable is the main concern. I suggest that the easiest way to program the loop is to use to determine when the two are in phase.
 
What is usually the case for generators connected to the grid for peak shaving? it may help somehow.

Thanks

Colin
 
Hrmmm, I doubt this would work for intelligent digitally controlled generators which push their output via electronics to clean the sine up
 
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