0
Effect of winding resistance with respect to EHV transformers voltage levels and their MVA rating?
Wiki User
∙ 14y ago
The MVA rating will have an effect on the winding resistance - the higher the rating, the bigger current flows, thus the larger winding wire must be, which lowers the resistance.
Generally, EHV Transformers impedance (the resistance value you're thinking of) is specified when ordering the transformer, and can range from 4-20% (on the transformer base rating).
When heavily loaded, on a weak system (high source impedance), the impedance of the transformer can impact the voltage level negatively (cause the voltage level, typically on the low side, to be less than desirable. I don't believe this is a serious concern, or the main reason to specify one impedance value versus another. Usually they are specified for cost, and other reasons (lower impedance must be able to withstand much more mechanical stress, while very high impedance may not provide enough fault current). On the EHV system, loads are typically "a ways away", and capacitor banks, inductor banks, and generators can be used to get the power to where it needs to go. Usually when it gets down to the loads that use it, it must go through at least one transformer that has an LTC (load tap changer) that can make corrections for any degradation in voltage. Often transformers with LTC's on the low sides have multiple taps on the high side as well to accommodate location in electrically weak locations.
Furthermore, recently I've seen a lot of "musical transformers" activities going on (moving one transformer from one site to another); these transformers have different impedances, and are put in drastically different locations (electrically). I have not heard anyone scream foul based on the transformer impedance causing voltage issues.
Disclaimer: My experience with transformer impedance choosing is not from a transmission planning perspective; my job does not usually entail dealing with voltage regulation. The planning people may do modelling that I do not know about to help in specification of impedance values.
Wiki User
∙ 14y ago
Add your answer:
Earn +20 pts
What happens to voltage in a step-down transformer?
The voltage induced into the secondary winding will be lower than the voltage applied to the primary winding. The primary winding being the winding connected to the supply, while the secondary winding is the one connected to the load.
How the input voltage is changed to an output voltage in a transformer?
Transformers work on the induction principal of the flux of the primary winding cutting the wires of the secondary winding. The amount of turns in the primary in relationship to the amount of turns in the secondary is the transformers winding ratio. This ratio is what governs the voltage value of the secondary winding.
What are the importance of step down transformers?
it decreases the high input voltage of its primary winding to a voltage level on secondary winding suitable for usage
When dc voltage is supplied to the primary coil of the transformer then the voltage be induced in secondary or not?
The windings of a transformer have both resistance and inductance. When you apply an AC voltage to the primary winding, the opposition to current flow is a combination of resistance and inductive reactance; although the resistance of the winding is relatively low, its inductive reactance is high. The resulting impedance (the vector sum of resistance and inductive reactance) will, therefore, be high and the resulting current will be low.If, on the other hand, you applied a DC voltage to the winding, the only opposition will be the low resistance of the winding. So, if the value of DC voltage is roughly the same as the rated AC voltage, a large value of current would result -high enough to probably burn out the winding.Since transformers work on the principle of mutual induction, a fluctuating magnetic field is necessary to induce a voltage into the secondary winding. Since a fluctuating magnetic field requires a fluctuating current, a transformer will only work if an AC voltage is applied to its primary winding.So, not only will a transformer not work when a DC voltage is applied to its primary winding, it will probably burn out the primary winding.
How do wall transformers work?
Just like any other transformer - voltage is applied to one winding, which induces a magnetic field in the transformer core, which induces a voltage on the other winding.
In a transformer primary or secondary will inside winding?
A step-down transformer's primary is high voltage and secondary is low voltage, based on voltage configuration or load we select which winding we do fast.In air-cooled Transformers output voltage is high and load current is low. So in air cooled low voltage winding in side and high voltage winding in out side of the coil . So we can reduce high voltage short problems and we can easily provide coil insulation . reduce short problem. It is cooled in oil.In step-down transformers we can do high voltage inside of the coil and low voltage and high current of the coil is outside. Because we can better coled in outer side . and reduced to temp problems.AnswerThe terms 'primary' and 'secondary' do not relate to a transformer's voltages, but to how its windings are connected. The primary winding is connected to the supply and the secondary winding is connected to the load. So, for a step-up transformer, the secondary winding is the higher-voltage winding while, for a step-down transformer, the secondary winding is the lower-voltage winding. Your question, therefore, should ask whether the higher- or the lower-voltage winding is the 'inside' winding (i.e. the winding closest to the core), and the answer is that it is the lower-voltage windings are innermost and the higher-voltage windings that are outermost.
When testing a power transformer with an ohmmeter which winding should have the largest ohmic value?
The higher-voltage winding has more turns (therefore its conductor will be longer) than the lower-voltage winding and, because it will carry less current, its conductors will have a lower cross-sectional area. Consequently, the higher-voltage winding will have a higher resistance than the lower-voltage winding.
What will happen if you give DC input to the primary of a transformers?
If DC voltage is applied to the primary of a transformer the flux produced in the transformer core will not vary but remain constant in magnitude therefore no emf will be induced in the secondary winding except at the time of switching on.Also there will be no self induced emf in the primary winding to oppose the applied voltage and since the resistance of the primary winding is quite low heavy current will flow through it which may result in burning out of primary winding.
Does a step-up transformer have a higher primary or secondary resistance?
It is a step up transformer since the secondary windings are greater than the primary. the turns ratio is (primary to secondary) 1:5, so the primary voltages is 1/5 of the secondary (5 volts).
What is the principle of operation of a ballast?
Older ballasts with an iron core are basically an autotransformer. They transform voltage to a higher voltage with a single winding. Electronic transformers increase voltage with capacitors and diodes.
The insulation resistance of a transformer winding can be easily measured with?
It depends on the rated voltage of the transformer winding -are you talking about a 12-V transformer winding or a 400-kV transformer winding? Obviously, there is no one answer to your question!
What is the conditon to connect a DC supply in primary of transformer?
Dc voltage level should not exceed the current carrying capacity of the winding. since winding resistance is very small. We need to be careful in giving the dc voltage to transformer winding.
