PLC based excitation controller for 750HP synchronous generator.

Thread Starter

UP Michigan

Joined May 3, 2019
4
Hello. Hope I'm in the right spot. I was wondering if anyone had an experience with a PLC based excitation controller for synchronous generator. I have received two bids for the excitation upgrade at a power plant. One firm specified a PLC based exciter and the other specified an application specific embedded controller. The PLC based controller worries me a little. First of all, in my opinion, its not typical. Second the controller looks "home made" in a sense. Since the industrial PLC is not capable of processing most of the external I/O from a generator they have to use over the counter transducers and modules to interface with the PLC. The company believes this to be an advantage and has referenced it's modular design and over the counter parts as evidence. I however see 40 different parts to make the same controller as the application specific controller does in one printed circuit board. Also the 40 different parts are composed of many different manufacturers. My gut feeling tells me this is an inferior system but the prices are so drastically different I'm worried management will not be able to over look that. Does any one have experience or opinion? Also, the application specific controller is a basler decs250. Thanks.
 

MaxHeadRoom

Joined Jul 18, 2013
20,730
Personally I would not think that a PLC would be a suitable for that application, the transducers are going to be needed whether PLC or embedded micro etc.
But the component count will certainly climb using the PLC, and IMO not a suitable fit at all.
Max.
 

oz93666

Joined Sep 7, 2010
737
A synchronous motor/generator is one which uses DC to create a magnetic field in the rotor

surely with the arrival of high power neodymium magnets that energy wasting rotor winding could be dispensed with??
 

Thread Starter

UP Michigan

Joined May 3, 2019
4
Personally I would not think that a PLC would be a suitable for that application, the transducers are going to be needed whether PLC or embedded micro etc.
But the component count will certainly climb using the PLC, and IMO not a suitable fit at all.
Max.
Thank you for your timely response sir. One thing to note is that the application specific controller directly accepts the external I/O. (P.T.s and C.Ts) and internally processes this information as opposed to separate external transducer. Do you see any obvious advantage of this? Thanks
 

Thread Starter

UP Michigan

Joined May 3, 2019
4
Personally I would not think that a PLC would be a suitable for that application, the transducers are going to be needed whether PLC or embedded micro etc.
B
A synchronous motor/generator is one which uses DC to create a magnetic field in the rotor

surely with the arrival of high power neodymium magnets that energy wasting rotor winding could be dispensed with??
A synchronous motor/generator is one which uses DC to create a magnetic field in the rotor

surely with the arrival of high power neodymium magnets that energy wasting rotor winding could be dispensed with??
ut the component count will certainly climb using the PLC, and IMO not a suitable fit at all.
Max.
Personally I would not think that a PLC would be a suitable for that application, the transducers are going to be needed whether PLC or embedded micro etc.
But the component count will certainly climb using the PLC, and IMO not a suitable fit at all.
Max.
A synchronous motor/generator is one which uses DC to create a magnetic field in the rotor

surely with the arrival of high power neodymium magnets that energy wasting rotor winding could be dispensed with??
In my opinion the problem with this is the lack of control of reactive power. It has been found preferable to regulate system voltage by adjusting field current to the rotor.
 

crutschow

Joined Mar 14, 2008
25,000
surely with the arrival of high power neodymium magnets that energy wasting rotor winding could be dispensed with??
You need control over the generator field to control the output voltage and power factor.

I have a motorcycle that has an alternator with a permanent magnet rotor, but the only way to control its voltage is to short circuit the generator with the regulator SCR's or transistors.
Very inefficient, and generates a lot of heat in the regulator (hot enough to burn skin).
I've had three regulator failures, apparently because they were under-designed to dissipate the heat.

That's why automotive alternators use an electromagnetic field that can be controlled, not a permanent magnet field.
 

oz93666

Joined Sep 7, 2010
737
In my opinion the problem with this is the lack of control of reactive power. It has been found preferable to regulate system voltage by adjusting field current to the rotor.
I guess system voltage is only regulated for about 5% on the top end ???? what about combining the two , use neodymium to create 95% of the field , with a small winding for extra if needed ??? This winding could also be reversed to reduce field by 5%.
 

Thread Starter

UP Michigan

Joined May 3, 2019
4
I guess system voltage is only regulated for about 5% on the top end ???? what about combining the two , use neodymium to create 95% of the field , with a small winding for extra if needed ??? This winding could also be reversed to reduce field by 5%.
It's also more then system voltage though. Often we will use are generators in power factor control. Purposely over exciting the generator 100-150% . It's unlikely that ability would be maintained with 95% flux density composed of permanent magnet. I have found an excellent explanation for the use of electro magnet in synchronous generator in the american electrician handbook. I believe chapter 7.40. Thank you.
 
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