Transformer Power Factor
Transformer Power Factor
(OP)
How is "primary power factor" affected by secondary (load) power factor?
Example: Power transformer with purely resistive load vs. all inductive load – say 0.8pf (What is pf seen by upstream distribution?)
Does pf vary/depend on the % loading of transformer?
Does pf vary/depend on the size of transformer?
Example: Power transformer with purely resistive load vs. all inductive load – say 0.8pf (What is pf seen by upstream distribution?)
Does pf vary/depend on the % loading of transformer?
Does pf vary/depend on the size of transformer?






RE: Transformer Power Factor
RE: Transformer Power Factor
The reason I ask is that two of the bigger claimed contributors to low power factor is motors and transformers. So transformers are not a big contributor to low pf unless they serve motors?
RE: Transformer Power Factor
There are special transformers for distribution that minimise the idling current, the Hexaformer is one that I have seen in operation.
Gunnar Englund
www.gke.org
RE: Transformer Power Factor
htt
An unloaded transformer appears as shown in Figure 2a, i.e. it is a lagging load formed by the parallel combination of the magnetising reactance and core loss 'resistance'. The magnetising reactance is dominant and the transformer appears as a small but highly inductive load when it is unloaded. The current drawn by the magnetising reactance is small relative to the rating of the transformer. If the transformer is grossly oversized compared to the load then the current in the parallel branch may form a sizeable fraction of the actual load on the transformer, and the overall power factor will suffer as a result.
The series elements of the Figure 1 model - the winding resistance and leakage reactance - also degrade the PF, but their impedances are usually much smaller than those of the load, and the load is therefore dominant in determining the power factor rather than the transformer.
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Experience is what allows us make a completely new mistake every day!
RE: Transformer Power Factor
Focus on reducing load pf and slightly overcorrect and you should be fine.
JTK