Power Quality Symptoms & Solutions e-book is is written from an electronics point of view, rather than a power engineering one. And in so doing, provides the bridge between theory and real life. According to the book introduction more and more lecturers are using this material as a reference in their courses. You can find lots of interesting reading here for many industry fields and links to other resources.
52 Comments
Tomi Engdahl says:
“There is a lot more DC on the mains now due to switch mode power supplies” – can you give reference that support this theory. Generally most switch mode power supplies don’t cause DC to mains. Switch mode power supplies were known to cause mains waveform distortion, that can in severe cases make transformers noisy. SMPS, by nature, draw current in pulses rather than a smooth sine wave, leading to a lower power factor. PFC circuits, often integrated into SMPS designs, reshape the input current to align more closely with the voltage waveform. The only SMPS I know that causes DC to mains are some very cheap low power chargers that have been built with half wave rectifier in mains input instead of proper full wave rectifier – those I have seen have been very low power (5W or less) so there would need to be very many of them near you for them to cause significant DC to mains.
Tomi Engdahl says:
Some power transformers hum when they are run slightly above the rated voltage. If you have a suitable multimeter, use it to measure your mains voltage. The UK spec. is 230V +10% -6% so you could be applying 253V to that 220-230V transformer.
It’s nothing to worry about, assuming the transformer does not get uncomfortably warm.