Impedance matching transformer question

In summary: If it is, the transformer is suitable for the application. If not, it is not suitable. In summary, the conversation discusses using a transformer for impedance matching in an application where a current of 6.0A to 6.5A needs to be passed through an impedance of (1.6 + 1.2i) ohms with only a 230V supply available. The transformer has a turns ratio of 16:1 and a laboratory test showed that with the secondary winding short-circuited, the input to the primary winding was 1A and 102.4W for an excitation voltage of 128V. The summary also mentions the need to determine if the transformer would be
  • #1
ch5497
2
0
1. It is required to pass a current of between 6.0A and 6.5A through an impedance of (1.6 + 1.2i) ohms. With only a 230V supply available, it is proposed to use a transformer for impedance matching. A transformer is available with a turns ratio of 16:1. A laboratory test showed that with the secondary winding short-circuited, the input to the primary winding was 1A and 102.4W for an excitation voltage of 128V.

Determine whether the transformer would be suitable for this application




2. None specified



3. So I've got the following so far;

P = I2R
102.4W = 12R
R = 102.4 ohms


V = IZ
128V = 1 . Z
Z = 128 ohms


X2= Z2-R2
X2= 1282-102.42
X = 384/5 = 76.8 ohms


Now, do I need to refer this impedance over to the secondary by multiplying by the turns ratio squared, and then add on the impedance given in the question? I could then find the current being drawn from the 230V and see if it's in the range required? I've done this, and gotten an answer, but without knowing if my method is correct, I don't know whether my decision on whether the transformer is suitable or not is accurate.

Thanks in advance.
 
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  • #2
ch5497 said:
1. It is required to pass a current of between 6.0A and 6.5A through an impedance of (1.6 + 1.2i) ohms. With only a 230V supply available, it is proposed to use a transformer for impedance matching. A transformer is available with a turns ratio of 16:1. A laboratory test showed that with the secondary winding short-circuited, the input to the primary winding was 1A and 102.4W for an excitation voltage of 128V.

Determine whether the transformer would be suitable for this application

2. None specified
3. So I've got the following so far;

P = I2R
102.4W = 12R
R = 102.4 ohmsV = IZ
128V = 1 . Z
Z = 128 ohmsX2= Z2-R2
X2= 1282-102.42
X = 384/5 = 76.8 ohms


Now, do I need to refer this impedance over to the secondary by multiplying by the turns ratio squared, and then add on the impedance given in the question?

No, you already know the impedance at the secondary, it's a short, remember? You should take the short off the secondary and put the 1.6 + 1.2i ohm impedance on the secondary instead. What impedance would you then see at the primary? Don't forget that with a short on the secondary you still have some impedance at the primary. That has to be added in.

ch5497 said:
I could then find the current being drawn from the 230V and see if it's in the range required?

There are two things you need to find.
1. You have to be sure the transformer can supply all the current that load requires and
2. if it can, is the load current in the range of 6 to 6.5 amps?

To find the first you have to transform the load impedance back to the primary to see how much current the primary will draw and then convert that into current available at the secondary.

To find the second calculate how much voltage there is at the secondary if the primary is connected to 230 V and calculate the current flowing through the load. If it is less than the available current, is it in the range of 6 to 6.5 amps?
 
  • #3


I can confirm that your method for determining the impedance and current in the secondary winding is correct. Multiplying the impedance by the turns ratio squared is the correct way to refer the impedance to the secondary winding.

To determine if the transformer is suitable for this application, we need to compare the secondary current with the required range of 6.0A to 6.5A. Using the formula I = V/R, we can calculate the current in the secondary winding as 230V / (102.4 + 76.8) ohms = 1.55A. This falls within the required range, indicating that the transformer would be suitable for this application.

However, it is important to note that the secondary current will change depending on the load connected to the transformer. So, it is important to ensure that the transformer can handle the maximum expected load without exceeding the current range. Additionally, other factors such as efficiency and voltage regulation should also be considered when determining the suitability of a transformer for a specific application.
 

1. What is an impedance matching transformer?

An impedance matching transformer is a device that is used to match the impedance of two different electrical circuits or components. It is designed to minimize signal reflection and maximize power transfer between the two circuits.

2. Why is impedance matching important?

Impedance matching is important because it ensures efficient transfer of energy between two electrical circuits. When the impedance is not matched, there can be signal reflections which can cause interference and reduce the overall performance of the circuit.

3. How does an impedance matching transformer work?

An impedance matching transformer works by altering the ratio of voltage to current in order to match the impedance of the two circuits. It essentially acts as a bridge between the two circuits, allowing for efficient transfer of energy.

4. When is an impedance matching transformer used?

An impedance matching transformer is used in a variety of applications, including audio systems, radio frequency circuits, and power distribution systems. It is especially important in high-frequency circuits where signal reflections can have a significant impact on performance.

5. How do I choose the right impedance matching transformer?

The right impedance matching transformer should have the same input and output impedance as the circuits you are trying to connect. It is also important to consider the frequency range and power handling capabilities of the transformer to ensure it can effectively match the impedance of the circuits in use.

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