- #1
Master1022
- 611
- 117
- Homework Statement
- Explain which sides each of the short/open-circuit tests are applied to on a step-up transformer and explain what circuit parameters can be deduced from them.
- Relevant Equations
- P = IV
Hi,
Question: I think my misunderstanding boils down to a few short questions:
1) Is the equivalent circuit for a transformer of the same topology for a step-up and step-down transformer?
I think it should be as the turns ratio is simply a constant.
2) How do the open/short-circuit tests work for a step-up transformer?
I have pasted this picture of an equivalent circuit from google. Usually I deal with problems that don't have [itex] R_1 [/itex] and [itex] X_1 [/itex] and all those impedances are included in [itex] R_2 [/itex] and [itex] X_2 [/itex] respectively. I will just refer to the '2' ones when talking about winding resistance and leakage reactance.
Attempt:
For the short circuit test, I understand that we want to achieve rated current and therefore measure the power dissipated by the winding resistance [itex] R_2 [/itex]. My lecture notes say that we want the rated current on the low voltage side and therefore apply the input voltage on the high voltage side, but only uses examples of a step-down transformer (for which the statement makes sense to me). Is this also true for step-up transformers? If it were, then that would mean that we apply the short circuit test input voltage to the 'secondary' (higher voltage end) and take measurements from the primary. However, wouldn't that mean that the primary was the side with [itex] R_2 [/itex] and [itex] X_2 [/itex]? Unless that means that we are measuring those secondary components referenced to the primary - is this the case (i.e. we are measuring [itex] (\frac{N_1}{N_2})^2 R_2 [/itex] and [itex] (\frac{N_1}{N_2})^2 X_2 [/itex] ). If that isn't the case, please let me know as that would mean that I have suggested a wrong implementation of the test.
For the open circuit test, I understand that we want to use rated voltage and measure the core losses due to [itex] R_0 [/itex] and [itex] X_0 [/itex]. We do this by applying a voltage at the lower voltage end such that rated voltage is obtained at the secondary end. Then we take measurements at the secondary. Following the above logic, does that mean that we are measuring: [itex] (\frac{N_2}{N_1})^2 R_0 [/itex] and [itex] (\frac{N_2}{N_1})^2 X_0 [/itex] (i.e. those 'primary' components referenced to the secondary)? Once again, please do correct me if I am wrong.
Any help is greatly appreciated as I am quite confused in this area.
Question: I think my misunderstanding boils down to a few short questions:
1) Is the equivalent circuit for a transformer of the same topology for a step-up and step-down transformer?
I think it should be as the turns ratio is simply a constant.
2) How do the open/short-circuit tests work for a step-up transformer?
I have pasted this picture of an equivalent circuit from google. Usually I deal with problems that don't have [itex] R_1 [/itex] and [itex] X_1 [/itex] and all those impedances are included in [itex] R_2 [/itex] and [itex] X_2 [/itex] respectively. I will just refer to the '2' ones when talking about winding resistance and leakage reactance.
Attempt:
For the short circuit test, I understand that we want to achieve rated current and therefore measure the power dissipated by the winding resistance [itex] R_2 [/itex]. My lecture notes say that we want the rated current on the low voltage side and therefore apply the input voltage on the high voltage side, but only uses examples of a step-down transformer (for which the statement makes sense to me). Is this also true for step-up transformers? If it were, then that would mean that we apply the short circuit test input voltage to the 'secondary' (higher voltage end) and take measurements from the primary. However, wouldn't that mean that the primary was the side with [itex] R_2 [/itex] and [itex] X_2 [/itex]? Unless that means that we are measuring those secondary components referenced to the primary - is this the case (i.e. we are measuring [itex] (\frac{N_1}{N_2})^2 R_2 [/itex] and [itex] (\frac{N_1}{N_2})^2 X_2 [/itex] ). If that isn't the case, please let me know as that would mean that I have suggested a wrong implementation of the test.
For the open circuit test, I understand that we want to use rated voltage and measure the core losses due to [itex] R_0 [/itex] and [itex] X_0 [/itex]. We do this by applying a voltage at the lower voltage end such that rated voltage is obtained at the secondary end. Then we take measurements at the secondary. Following the above logic, does that mean that we are measuring: [itex] (\frac{N_2}{N_1})^2 R_0 [/itex] and [itex] (\frac{N_2}{N_1})^2 X_0 [/itex] (i.e. those 'primary' components referenced to the secondary)? Once again, please do correct me if I am wrong.
Any help is greatly appreciated as I am quite confused in this area.