Synchronous Motor as Reactive Power Source
Synchronous Motor as Reactive Power Source
(OP)
Hello.
I have a 3000 KW Synchronous Motor. Made by KATO. I replace this motor with a wound rotor motor. I'm thinking to install the synchronous motor as a Reactive Power Source, in order to improve the PF. The plant is a big consumer, almost a 42 MW, The incoming has two transformers and its feeders, seven in each one, one for each section. I'm thinking to install the motor after one of these feeders. We have the biggest induction motors downstream of one of the principal transformer.
Do you have any thoughts about it? I'll appreciate if any of you could give some ideas about to implement it or if you have some experience about the topic.
Regards.
I have a 3000 KW Synchronous Motor. Made by KATO. I replace this motor with a wound rotor motor. I'm thinking to install the synchronous motor as a Reactive Power Source, in order to improve the PF. The plant is a big consumer, almost a 42 MW, The incoming has two transformers and its feeders, seven in each one, one for each section. I'm thinking to install the motor after one of these feeders. We have the biggest induction motors downstream of one of the principal transformer.
Do you have any thoughts about it? I'll appreciate if any of you could give some ideas about to implement it or if you have some experience about the topic.
Regards.





RE: Synchronous Motor as Reactive Power Source
RE: Synchronous Motor as Reactive Power Source
Roy
RE: Synchronous Motor as Reactive Power Source
DPC. We have this motor out of services, and I expect that the improvement in the PF will be a benefit. This motor has sleeve bearings, and when it had been loaded, it didn't need to much maintenance. Just checking the air filters, changing the oil time to time when the analysis said that it begins to get degraded. I have measurements that when the motor has no load it has 100 KW.
Roydm. What kind of control or equipment do you had been used to control the excitation of the motor, I'm thinking about a Basler equipment.
Any idea will be appreciate.
Regards.
RE: Synchronous Motor as Reactive Power Source
Keith Cress
kcress - http://www.flaminsystems.com
RE: Synchronous Motor as Reactive Power Source
Actually there is a penalty over the bill of energy, if we have a low PF. I'm not have the exactly value, but it is below 0.75 lag or so. We have almost this value, due to the inductive motors that we have. So I'm looking for a solution, but I don't like the idea to use capacitor, because in some time we don´t have all the plant running, and in some time we have to many motor running so the PF get below 0.75.
The installation of the motor could be a great solution, using a Basler o other controller, that sense the PF of the line, and controls the reactive power that the motor produce.
Regards.
RE: Synchronous Motor as Reactive Power Source
This was over 40 years ago, the starter and exitation were strictly manual and our pf was so bad we couldn't have enough correction.
The motor was 100 HP and could be coupled to a compressor by flat belt drive.
I expect it was dated from the 40s
Roy
RE: Synchronous Motor as Reactive Power Source
Bill
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"Why not the best?"
Jimmy Carter
RE: Synchronous Motor as Reactive Power Source
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If we learn from our mistakes I'm getting a great education!
RE: Synchronous Motor as Reactive Power Source
Would that ever happen Scotty?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Synchronous Motor as Reactive Power Source
Not sure - distribution ain't really my field. Generators are certainly paid for their reactive capability. Someone like David Beach will hopefully comment.
42MW at a 0.75pf is a pretty awful load and adding 3MVAr isn't going to improve it by much, only to about 0.78 or so.
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If we learn from our mistakes I'm getting a great education!
RE: Synchronous Motor as Reactive Power Source
RE: Synchronous Motor as Reactive Power Source
We consider the use of a back of capacitors. But right now we would like to get almost the reactive power that the motor gave to us, when it was installed.
It would be installed downstream the transformer that have the largest motors.
RE: Synchronous Motor as Reactive Power Source
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If we learn from our mistakes I'm getting a great education!
RE: Synchronous Motor as Reactive Power Source
We replace the synchronous motor for a wound rotor motor, because the inrush current and for the torque of the load, a vertical mill. So with the wound rotor motor, we can manage the inrush current. With the synchronous motor, we have the problem that the principal transformer is near of its capacity, and we have to put our emergency generators online, to manage the voltage line. And the torque of the synchronous motor are pretty low for the application. So we decide to replace the motor, and one of the options is a wound rotor motor from Siemens. But this options increase the reactive power that we need. Siemens is trying to put a bank of capacitor for this motor, to compensate the reactive. And we obtain fron the synchronous motor more that the siemens motor needs.
Regards.
RE: Synchronous Motor as Reactive Power Source
Thanks all!
Keith Cress
kcress - http://www.flaminsystems.com
RE: Synchronous Motor as Reactive Power Source
new MVAr = 27.78 - 3 = 24.78;
new MVA = sqrt(42^2+24.78^2) = 48.76 MVA
And the new PF = 42/48.76 = 0.86
I guess most utilities penalize plants operating below 0.85, depends on the area though.
RE: Synchronous Motor as Reactive Power Source
42MW at 0.75 PF = 56MVA = 42MW + 37MVAr.
42MW + (37 -3)MVAr = 54MVA
54MVA = 42MW at 0.777 PF
One of us is wrong!
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If we learn from our mistakes I'm getting a great education!
RE: Synchronous Motor as Reactive Power Source
RE: Synchronous Motor as Reactive Power Source
RE: Synchronous Motor as Reactive Power Source
Yes it works, but it is very expensive. In many plants, especially plants with a high diversity factor, the cost of individual correction versus bulk correction is several times. The greater the diversity factor, the greater the difference. For power factor correction there is no "One size fits all" solution. Utility penalties kick in at any where from 85% or 90% lagging to 99% leading or lagging in different countries. Calculation of power factor may be a dynamic summation in real time or a monthly reconciliation of KWHs and KVARHs. The monthly method allows a small corrrection to be online 24 hrs a day.
Your rule of thumb may be valid but be aware that it is the most expensive solution to power factor correction.
Bill
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"Why not the best?"
Jimmy Carter
RE: Synchronous Motor as Reactive Power Source
You are absolutly right. I just put it out there to see what responce I would get. Reading the posts about near compacity tranf and starting generators. Didn't give me a warm comfortable feeling. I would have to know more about the plant system. I have a feeling that this is and old plant and have over sized motors. This is a very interesting field with PF, VFD, harmonics, solid state relays, gen controls.
RE: Synchronous Motor as Reactive Power Source
Sorry, must be sleepy! You are correct!