DISTRIBUTION TRANSFORMERS HARMONICS AND DC EFFECTS BASIC INFORMATION
What Are The Harmonics And DC Effects Of Distribution Transformers?
Harmonics and DC Effects
Rectifier and discharge-lighting loads cause currents to flow in the distribution transformer that are not pure power-frequency sine waves. Using Fourier analysis, distorted load currents can be resolved into components that are integer multiples of the power frequency and thus are referred to as harmonics.
Distorted load currents are expected to be high in the 3rd, 5th, 7th, and sometimes the 11th and 13th harmonics, depending on the character of the load.
Odd-Ordered Harmonics
Load currents that contain the odd-numbered harmonics will increase both the eddy losses and other stray losses within a transformer. If the harmonics are substantial, then the transformer must be derated to prevent localized and general overheating.
ANSI standards suggest that any transformer with load current containing more than 5% total harmonic \ distortion should be loaded according to the appropriate ANSI guide (IEEE, 1998).
Even-Ordered Harmonics
Analysis of most harmonic currents will show very low amounts of even harmonics (2nd, 4th, 6th, etc.) Components that are even multiples of the fundamental frequency generally cause the waveform to be nonsymmetrical about the zero-current axis.
The current therefore has a zeroth harmonic or dc-offset component. The cause of a dc offset is usually found to be half-wave rectification due to a defective rectifier or other component.
The effect of a significant dc current offset is to drive the transformer core into saturation on alternate half-cycles. When the core saturates, exciting current can be extremely high, which can then burn out the primary winding in a very short time.
Transformers that are experiencing dc-offset problems are usually noticed because of objectionably loud noise coming from the core structure. Industry standards are not clear regarding the limits of dc offset on a transformer.
A recommended value is a dc current no larger than the normal exciting current, which is usually 1% or less of a winding’s rated current (Galloway, 1993).
CAN 60 HZ TRANSFORMERS BE OPERATED AT 50 HZ? BASICS AND TUTORIALS
AN ANSWER TO THE QUESTION
CAN 60 HZ TRANSFORMERS BE OPERATED AT 50 HZ?
Will A 60 Hz Transformers
Work at 50 Hz? Answers and Links
Transformers rated below 1
KVA cab be used on 50 Hz service. Transformers 1 KVA and larger,
rated at 60 Hz, should not be used on 50 Hz service due to the higher
losses and resultant heat rise. Special designs are required for this
service. However, any 50 Hz transformer will operate on a 60 Hz
service.
Other Answers and Opinion on
this query can be found below:
Can transformers be
operated at various frequencies?
A 60 Hz design is normally
smaller than a 50 Hz design. For kind information please DO NOT use
60 Hz rated transformers on 50 Hz service. Without exacting designs,
higher losses and greater heat rise will result. Operating 60 Hz
transformers at higher frequencies may simply give less voltage
regulation.
Source:
http://www.custompowertransformer.com/Faq.html
Can 60 Hz transformers be
used on 50 Hz?
Yes. 60 Hz transformers can
be used on 50 Hz if special precautions are taken. The change in
frequency will impact the flux density of the transformer causing it
to run hot, as if it were overloaded. To offset this effect, you must
decrease the input voltage by approximately 17% (1/6th). This means
that a transformer rated for a 480 Volt, 60 Hz input could run at 50
Hz but with a maximum input voltage of 398 volts.
Source:
http://www.experts123.com/q/can-60-hz-transformers-be-used-on-50-hz.html
Can 60 Hz transformers be
operated at 50 Hz?
Transformers 1 KVA and
larger, rated at 60 Hz, should not be used on 50 Hz service due to
higher losses and resultant heat rise. However, any 50 Hz transformer
will operate on 60 Hz service.
Source:
http://www.mgmtransformer.com/faq/can-60-hz-transformers-be-operated-at-50-hz/
You might ask, why is it
that there is a variation in frequency?
History, politics, and
science is the reason. To know what we mean, visit this site for a
well thought answers.
http://www.school-for-champions.com/science/ac_world_volt_freq.htm
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