No load condition of energized tranformwer
No load condition of energized tranformwer
(OP)
We are shutting down the major loads on 5MVA transformer (25kV/4.16KV), which will be slightly loaded eventually(almost no-loaded). The power factor at the primary feeder will be higher because of the no-load condition. Do we need to correct the power factor for this feeder because of the shedding the loads? To me, the power factor for 25kV system will be higher than before. Are there any other negative impact because of this unloaded conditions?
Do we need to reduce the no load current in an egergized transformer?
Thanks in advance for any inputs.
Do we need to reduce the no load current in an egergized transformer?
Thanks in advance for any inputs.






RE: No load condition of energized tranformwer
RE: No load condition of energized tranformwer
Check the load power factor at your new loading condition and see if it too low or too high.
RE: No load condition of energized tranformwer
respectfully
RE: No load condition of energized tranformwer
RE: No load condition of energized tranformwer
RE: No load condition of energized tranformwer
respectfully
RE: No load condition of energized tranformwer
If you have the transformer test data, you can probably calculate the no-load power factor.
RE: No load condition of energized tranformwer
You convert the primary no-load current to secondary current (acc to volt ratio) and use a capacitor on the secondary to compensate this current.
Doesn't your primary side have metering where you can read the pf directly ?
*Why a man thinks he outrun a chasing dog when it has twice as many legs?*
RE: No load condition of energized tranformwer
The above figures can be verified from transformer test reports.Net pf on the grid due to transformer depends on load pf plus no-load pf.But the effect of load pf alone will be significant as the no-load kVA is negligible.So load pf improving capacitors can be switched off during no-load operation.
RE: No load condition of energized tranformwer
The power factor is very low because the only loss is from the core loss of the transformer, which is almost purely inductive.
To reduce no-load current in an energized tranformer, a two terminal control and power swicthing circuit for reducing electric current flow in the primary winding when no load is connected can be utilized, which is called Triac, in series with the power transformer primary and utility. But I am not sure about the price range and practicablity about this.
RE: No load condition of energized tranformwer
Any actual energy loss in the transformer must result in in-phase current, not inductive.
I believe prc is correct in stating that the transformer no-load current will not be highly inductive.
In reviewing transformer test data for a 12/16/20 MVA 110 kV transformer, I come up with a power factor of about 0.85 for no-load current, which is 0.18% of the rated current.
The main concern with a lightly loaded transformer is generally the core losses, since these are constant regardless of transformer load.
RE: No load condition of energized tranformwer
RE: No load condition of energized tranformwer
RE: No load condition of energized tranformwer
Any true loss (watts) has to be related to current in phase with the voltage. The term "reactive loss" is not accurate. For a hypothetical pure reactance, there would be no loss.
RE: No load condition of energized tranformwer
But there is still a power consumption due to excitation current.
RE: No load condition of energized tranformwer
Reactive loss is a bad term because it is generally used for the load current flowing through the transformer reactance.
In any case, as far as feeder overall power factor is concerned, the current may be exciting, but it not significant.
RE: No load condition of energized tranformwer
RE: No load condition of energized tranformwer
As mentioned a couple of times previously, your assumption that Ih is very small compared with Im is not supported by the facts as shown in transformer test data.
But more importantly, what is your point? No one said that Ie was purely real.
RE: No load condition of energized tranformwer
HamidEle, please see attached link, I'm hope it's help
http:/
Regards.
Slava
RE: No load condition of energized tranformwer
Slavag.