0
Transformer polarity is the direction the secondary goes relative to the primary, or relative to another secondary. Usually, polarity does not matter, for example in the case where the secondary is connected to a rectifier / filter / regulator. Sometimes, it does matter, particularly if there are two secondaries used to provide DC isolation between a preamp and a final amplifier in push-pull configuration. It can also matter if the overall circuit is involved in a feedback loop and phase inversion is a factor.
Answer
When applied to Transformers, the term 'polarity' describes the direction in which the secondary voltage is acting relative to the direction of the primary voltage. Polarity is determined by the directions in which the primary and secondary windings are wound relative to each other.
Polarity is described as being either 'additive' or 'subtractive', and can be determined by of connecting one pair of primary and secondary terminals together. If the voltage measured between the other adjacent primary and secondary terminals is greater than the primary voltage, then the transformer has 'additive' polarity; if the voltage is less than the primary voltage, then the transformer has 'subtractive' polarity.
Knowing the polarity of individual transformers is important when two single-phase transformers are connected in parallel with each other because, if polarity is ignored, then an incorrect connection might result, causing a large circulating current through the two secondary windings.
Wiki User
∙ 9y ago
Wiki User
∙ 10y agoThe 'polarity' of a transformer describes the direction of the secondary voltage with respect to the primary voltage. This depends on the relative directions in which each of the windings have been wound. Polarity is a very important factor when two transformers are to be connected in parallel with each other in much the same way as the polarities of two batteries are.
To determine the polarity of a transformer, the high- and low-voltage windings are connected in series, and a small voltage is applied to the high-voltage windings. If the voltage then appearing across both windings is greater than the applied voltage, then we describe the transformer as having 'additive' polarity; if, on the other hand, the resulting voltage is lower than the applied voltage, then we describe the transformer as having 'subtractive' polarity.
In North America, with the high-voltage windings on the far side of the transformer from the viewer, if the diagonally-opposite terminals both 'go positive' at the same instant then the transformer is 'additive' polarity; if the directly-opposite terminals 'go positive' at the same instant, the transformer is 'subtractive' polarity.
Add your answer:
Earn +20 pts
What is the aim of doing polarity test on the transformer?
Knowing the polarity of transformers is important if they are to be connected in parallel.
Why is the polarity of the output and input is same in ac transformer?
polarity play essential role in protection purpose if you have done wrong polarity in yours system then protection will operate under normal operationFurther AnswerThe polarity of a single-phase transformer describes the phase relationship of the secondary voltage relative to the primary voltage. Polarity is described as being either 'additive' or 'subtractive'. Knowing a transformer's polarity is one of the essential requirements for paralleling a pair of individual transformers.
What is the procedure to polarity test a 3 phase transformer?
A 'polarity test' is conducted on a single-phase transformer, not a three-phase transformer (or transformer bank). The polarity of a single-phase transformer being important if two transformers are to be connected in parallel, or three transformers are going to be connected to form a three-phase transformer bank.'Angular displacement' is, to a three-phase transformer, what 'polarity' is to a single-phase transformer. So you really should be asking about angular displacement, rather than polarity. Angular displacement, or 'phase displacement', is the angle by which the secondary line voltage lags the primary line voltage.Angular displacement can be determined either by drawing a phasor diagram of the three-phase connection and measuring it, or by looking up the connection in a vector-group chart/table -you would nor normally 'calculate' angular displacement.
What is dot polarity in 3 phase transformer?
Let's first talk about 2 winding transformer Say side a a' and b b' So dot polarity tells us that when a is at higher potential then a' at that instant which among b and b' is at higher potential So if in a fig dot is over a on a a' side and over b' on b b' side then at the instant when a is at higher potential then a' at that time b' will be at higher potential than b Imagine we connect three such single phase two winding transformers having dot polarity marked, in delta(or star) Now we have a three phase transformer with dot polarity.
Why do you do polarity test of transformers?
Yes, transformers have polarity. ADDED. They do in the sense of Live and Neutral or earth-tapping arrangement in a mains wiring system, but otherwise they are not considered to do so because they handle only alternating, not direct, current. So their voltage and magnetic polarities alternate, rather than staying constant.
What happen when the polarity of transformer reversed?
You cannot 'reverse' the polarity of a transformer -it is either wound with 'additive polarity' or 'subtractive polarity', and there's not much you can do about it! For a single transformer, its polarity doesn't really matter. But if you are going to parallel two transformers, then you must know the polarity of each transformer in order to avoid harmful circulating currents in their secondary windings.
Why the polarity of transformer is important?
a polarity test is a test which use to check the polarity of tranformer.the rision of this test to running the two or more transformer in parallel.like bettry situation or to fin the terminals
What is the aim of doing polarity test on the transformer?
Knowing the polarity of transformers is important if they are to be connected in parallel.
Why is the polarity of the output and input is same in ac transformer?
polarity play essential role in protection purpose if you have done wrong polarity in yours system then protection will operate under normal operationFurther AnswerThe polarity of a single-phase transformer describes the phase relationship of the secondary voltage relative to the primary voltage. Polarity is described as being either 'additive' or 'subtractive'. Knowing a transformer's polarity is one of the essential requirements for paralleling a pair of individual transformers.
What is the procedure to polarity test a 3 phase transformer?
A 'polarity test' is conducted on a single-phase transformer, not a three-phase transformer (or transformer bank). The polarity of a single-phase transformer being important if two transformers are to be connected in parallel, or three transformers are going to be connected to form a three-phase transformer bank.'Angular displacement' is, to a three-phase transformer, what 'polarity' is to a single-phase transformer. So you really should be asking about angular displacement, rather than polarity. Angular displacement, or 'phase displacement', is the angle by which the secondary line voltage lags the primary line voltage.Angular displacement can be determined either by drawing a phasor diagram of the three-phase connection and measuring it, or by looking up the connection in a vector-group chart/table -you would nor normally 'calculate' angular displacement.
What will happen if the transformers working in parallel are not connected with regard to polarity?
when two transformer are connected in parallel condition,and the polarity of transformer are opposite to each other then a large circulating current flow through out the winding,therefore a very small current flow thro, the load .therefore lifespan of transformer will be reduced.
Is polarity important with fluorescent under cabinet lights?
Yes, polarity is always important. Many under cabinet fluorescent fixtures are small enough to use a small transformer rather than a ballast. But even then, the transformer will have a longer life if it's wired with correct polarity.
Why transformers do not have poles even though it has magnetic field?
The windings of a transformer do have poles, which alternate in polarity in step with the A.C. magnetising current. As the polarity of the poles reverse, so too does the direction of the magnetic flux within the transformer's core.
What is transformer polarity?
'Polarity' describes the sense (direction) in which the voltage (not current!) induced into secondary winding is acting, relative to the sense in which the voltage applied to the primary winding is acting.In North America, a transformer's high-voltage winding terminals are identified by the letter H, and the low-voltage winding terminals by the letter X. In the case of a two-winding transformer, the pair of high-voltage terminals are marked H1 - H2, and the pair of low-voltage terminals are marked X1 - X2.When the potential of HV terminal H1 'goes positive' (i.e. during the first half-cycle of AC), if LV terminal X1 also goes positive at the same time, then the transformer is an 'additive polarity' transformer. On the other hand, if terminal X2 goes positive at the same time as H1, then the transformer is a 'subtractive polarity' transformer.Knowing the polarity of a transformer is very important if you intend to operate transformers in parallel with each other (there are other factors, too, of course), in the same way as it is important to know the polarity of a battery before you can connect it in parallel with another battery.
What is the use of polarity test?
I will assume that your question is in reference to CT and transformer polarity.In the case of a CT (Current Transformer) they have to be installed in the correct direction for proper metering. The polarity check is used to verify that they are installed correctly and that the polarity marks are correct (if the CT has them).In the case of a transformer there are two types of polarity, additive and subtractive. If you are paralleling transformers you have to ensure that they are the same type polarity in addition to other attributes.Hope this helps.Alternative AnswerIn a new electrical installation, a polarity test is conducted to ensure that socket outlet terminals are correctly wired (line really is line, neutral really is neutral, and the protective conductor (earth/ground) really is protective conductor. It's also important, for example, that the centre pin on an Edison Screw lampholder is connected to line, and not to neutral.
What is dot polarity in 3 phase transformer?
Let's first talk about 2 winding transformer Say side a a' and b b' So dot polarity tells us that when a is at higher potential then a' at that instant which among b and b' is at higher potential So if in a fig dot is over a on a a' side and over b' on b b' side then at the instant when a is at higher potential then a' at that time b' will be at higher potential than b Imagine we connect three such single phase two winding transformers having dot polarity marked, in delta(or star) Now we have a three phase transformer with dot polarity.
Why do you do polarity test of transformers?
Yes, transformers have polarity. ADDED. They do in the sense of Live and Neutral or earth-tapping arrangement in a mains wiring system, but otherwise they are not considered to do so because they handle only alternating, not direct, current. So their voltage and magnetic polarities alternate, rather than staying constant.
