Centered-tapped transformer in Simscape unexpected behaviour

Hi Dear community,

I am working with the simscape toolbox in simulink.

I am trying to use the Center-tapped transformer, but the output voltage is not following the turn ratio value.

I try to forced the winding ratio value in order to match my expected output voltage but that is not really good.

The input voltage betwen the center tab and port 1 (vLm1)

The output voltage between port 4 a 5 (vSec)

The input current through port 1 (iLm1)

The output current thorugh port 4 (iSec)

My turn ration is Ns/Np = 3, Thus I would expect to see the voltage like:

vSec = vLm1*Ns/Np = 12.5V*3 = 37.5 , but I am having 75 (twice than the expected value).

For the current I observed the same problem, iSec = iLm1/6 istead of 3.

I performed the simulation using the 3 winding mutal inductances, arranging the values to simulate the transformer operation.

The results are consistent with the performance of the transformer of turn ration = 3

For example for Vsec/Vlm1 = 3 , and for iLm1/Isec = 3.

I hope somebody already has a solution for the Centered-tapped . Let's hope for the best!

[Poorna]

Hi Romy,

You haven't mentioned anything about the 2+ port of the center-tapped transformer. Have you connected the 2+ port( port 2) with the 2- port(port 1)?

[Romy]

Hi @Poorna,

Port 2 is connected to my switch element 1, port 1 is connected to my switch element 2, and center tab (port 3) is connected to GND (electrical referece)

Answer 1

[Vinay]

Hii Romy,

The output voltage is twice of the expected value is due to the centre tap in the transformer present at the secondary winding, because it divides the winding into two equal parts so both parts have equal number of turns.

The “Winding ratio” parameter for the transformer is defined as the ratio of primary winding to the secondary winding.

So, the Np/Ns = 3 for the model.

As per the data provided in the question:

VLm1 = 12.5 volts is the secondary voltage (port 1 and tap) and the output voltage (port 4 and port 5) is the primary voltage for the transformer.

Vsecondary = (Ns/Np) *Vprimary

Vsecondary1 = (Ns1/Np) *Vprimary

In the model “VLm1” is the secondary voltage so,

VLm1 = (Ns1/Np) *Vprimary

Vprimary = (VLm1) *(Np/Ns1)

Since Ns1 = Ns/2

Vprimary = (VLm1) *(2*Np/Ns)

Vprimary = 12.5*2*3 = 75 volts

The issue is occurring because the transformer takes winding ratio as ‘Np/Ns’

But you are giving the ratio as ‘Ns/Np’ and central tap divides the winding into two parts causing the factor of 2 in the result

Kindly refer to the below documentation of “Center-Tapped Transformer”:

https://in.mathworks.com/help/releases/R2023b/sps/ref/centertappedtransformer.html