• Latest
  • Trending
  • All
  • Capacitors
  • Resistors
  • Inductors
  • Filters
  • Fuses
  • Non-linear Passives
  • Applications
  • Integrated Passives
  • Oscillators
  • Passive Sensors
  • New Technologies
  • Aerospace & Defence
  • Automotive
  • Industrial
  • Market & Supply Chain
  • Medical
  • RF & Microwave
  • Telecommunication

Transformer Testing, Parasitic Inductors/Capacitance & Lab traps

10.10.2023

Heating of Power Inductors in Switching Regulators

6.12.2023

KYOCERA AVX Industry’s First Automotive MLV Varistors with Flexible Terminations Meets Both AEC-Q200 and VW Standards

6.12.2023

Digital WE Days 2023 Virtual Conference Celebrates Record Participation

5.12.2023

DigiKey Launches its 15th Annual DigiWish Giveaway

5.12.2023

Lithium Mines Impact to Tantalum Supply

5.12.2023

Bourns Announces Four New High Power Ultra-Low Ohmic Current Sense Resistors

4.12.2023
  • Home
  • Privacy Policy
  • EPCI Membership & Advertisement
  • About
No Result
View All Result
NEWSLETTER
Passive Components Blog
  • Home
  • NewsFilter
    • All
    • Aerospace & Defence
    • Antenna
    • Applications
    • Automotive
    • Capacitors
    • Circuit Protection Devices
    • Filters
    • Fuses
    • Inductors
    • Industrial
    • Integrated Passives
    • Market & Supply Chain
    • Market Insights
    • Medical
    • New Materials & Supply
    • New Technologies
    • Non-linear Passives
    • Oscillators
    • Passive Sensors
    • Resistors
    • RF & Microwave
    • Telecommunication
    • Weekly Digest

    Heating of Power Inductors in Switching Regulators

    KYOCERA AVX Industry’s First Automotive MLV Varistors with Flexible Terminations Meets Both AEC-Q200 and VW Standards

    Digital WE Days 2023 Virtual Conference Celebrates Record Participation

    DigiKey Launches its 15th Annual DigiWish Giveaway

    Lithium Mines Impact to Tantalum Supply

    Bourns Announces Four New High Power Ultra-Low Ohmic Current Sense Resistors

    November 2023 ECIA NA Electronic Components Sales Sentiment Setback in Attempted Recovery

    Wk 49 Electronics Supply Chain Digest

    Optimizing Tantalum Capacitor Manufacturing Through Yield Strength and Plasticity Analysis in Welding Processes

    Trending Tags

    • Ripple Current
    • RF
    • Leakage Current
    • Tantalum vs Ceramic
    • Snubber
    • Low ESR
    • Feedthrough
    • Derating
    • Dielectric Constant
    • New Products
    • Market Reports
  • VideoFilter
    • All
    • Antenna videos
    • Capacitor videos
    • Filter videos
    • Fuse videos
    • Inductor videos
    • Non-linear passives videos
    • Oscillator videos
    • Passive sensors videos
    • Resistor videos
    • Sensors

    Heating of Power Inductors in Switching Regulators

    Addressing EMC Issues; Texas Instruments and Würth Elektronik Webinar

    DC-Link Film Capacitors for DC-Charger Applications; WE Webinar

    Transformer Design for EMC; WE Webinar

    Filter Calculation and Selection with REDEXPERT EMI Filter Designer; WE Webinar

    Experimental Demonstration of Inductor Back Electromotive Force EMF

    Charging/Discharging of Linear andNon-linear Capacitors

    How to Select Inductor For Switching Power Supply

    Oscillators Integration, Selection Guide and Design In

    Trending Tags

    • Capacitors explained
    • Inductors explained
    • Resistors explained
    • Filters explained
    • Application Video Guidelines
    • EMC
    • New Products
    • Ripple Current
    • Simulation
    • Tantalum vs Ceramic
  • Knowledge Blog
  • Suppliers
    • Preferred Suppliers
    • Who is Who
  • Events
  • Home
  • NewsFilter
    • All
    • Aerospace & Defence
    • Antenna
    • Applications
    • Automotive
    • Capacitors
    • Circuit Protection Devices
    • Filters
    • Fuses
    • Inductors
    • Industrial
    • Integrated Passives
    • Market & Supply Chain
    • Market Insights
    • Medical
    • New Materials & Supply
    • New Technologies
    • Non-linear Passives
    • Oscillators
    • Passive Sensors
    • Resistors
    • RF & Microwave
    • Telecommunication
    • Weekly Digest

    Heating of Power Inductors in Switching Regulators

    KYOCERA AVX Industry’s First Automotive MLV Varistors with Flexible Terminations Meets Both AEC-Q200 and VW Standards

    Digital WE Days 2023 Virtual Conference Celebrates Record Participation

    DigiKey Launches its 15th Annual DigiWish Giveaway

    Lithium Mines Impact to Tantalum Supply

    Bourns Announces Four New High Power Ultra-Low Ohmic Current Sense Resistors

    November 2023 ECIA NA Electronic Components Sales Sentiment Setback in Attempted Recovery

    Wk 49 Electronics Supply Chain Digest

    Optimizing Tantalum Capacitor Manufacturing Through Yield Strength and Plasticity Analysis in Welding Processes

    Trending Tags

    • Ripple Current
    • RF
    • Leakage Current
    • Tantalum vs Ceramic
    • Snubber
    • Low ESR
    • Feedthrough
    • Derating
    • Dielectric Constant
    • New Products
    • Market Reports
  • VideoFilter
    • All
    • Antenna videos
    • Capacitor videos
    • Filter videos
    • Fuse videos
    • Inductor videos
    • Non-linear passives videos
    • Oscillator videos
    • Passive sensors videos
    • Resistor videos
    • Sensors

    Heating of Power Inductors in Switching Regulators

    Addressing EMC Issues; Texas Instruments and Würth Elektronik Webinar

    DC-Link Film Capacitors for DC-Charger Applications; WE Webinar

    Transformer Design for EMC; WE Webinar

    Filter Calculation and Selection with REDEXPERT EMI Filter Designer; WE Webinar

    Experimental Demonstration of Inductor Back Electromotive Force EMF

    Charging/Discharging of Linear andNon-linear Capacitors

    How to Select Inductor For Switching Power Supply

    Oscillators Integration, Selection Guide and Design In

    Trending Tags

    • Capacitors explained
    • Inductors explained
    • Resistors explained
    • Filters explained
    • Application Video Guidelines
    • EMC
    • New Products
    • Ripple Current
    • Simulation
    • Tantalum vs Ceramic
  • Knowledge Blog
  • Suppliers
    • Preferred Suppliers
    • Who is Who
  • Events
No Result
View All Result
Passive Components Blog
No Result
View All Result

Transformer Testing, Parasitic Inductors/Capacitance & Lab traps

10.10.2023
Reading Time: 9 mins read
A A

In this article Frenetic power electronics engineer Sotiris Zorbas, MSc shares his personal experience with transformer testing and what he called “Lab traps” focusing in particular on the importance of parasitic inductors/capacitance in the secondary side of transformers.

60W Flyback Transformer Case Study

I used a flyback PSU capable of delivering 60W as an transformer test case study.

RelatedPosts

How to Select Ferrite Cores

How to Optimize Magnetizing Inductance for ZVS Zero Volt Switching

To Be Planar or Not To Be

Because the board transformer had a different pinout, I used some round 0.7mm solid wires to extend the pins of my sample.

This is how the transformer looked like at the beginning of the experiment:

Table 1. Transformer basic specs under test
Figure 1. 30mm-0.7mm wires used to quickly mount the transformer to the flyback circuit

Then I started the tests, raising the power at the electronic load to reach 60W @ 20V. But, in fact, I couldn’t do it… the flyback controller was shutting down after about 40-45W!

When wondering what had just happened, these were my first ideas:

  • I failed selecting the proper turns ratios in the design stage.
  • I got confused specifying pinout in Frenetic Online.
  • The guys in the lab that built the sample missed something.

After checking the validation sheet that each sample gets and performing some more testing, neither of the ideas mentioned above were true, except one spec! In the validation sheet that I had in front of me, the leakage inductance didn’t match the one in my measurement. To be exact at 60-100kHz range the leakages measured are listed in Table 2.

Table 2. Differences measuring leakage inductance for the same sample

Note that the leakage inductance is the one of the secondary, as it is measured reflected back to the primary. That is easily done by shorting the secondary and taking an inductance measurement of the primary. The two values are measured at 2 different frequencies, so I couldn’t make a good comparison.

Then I remembered that the controller board mentioned could tolerate up to 5uH of leakage. The original transformer had a leakage inductance of approximately 4.7uH. With 6-7.5uH the design was probably triggering the controller protection, and thus the shutdown after 40-45W.

OK, that might be the reason why. But what’s really happening with leakage inductance? What’s the true value? 

Transformer Test Result Evaluation

I took the transformer completely apart and rewind it using round wires. This time I didn’t care for isolation, as functional isolation would be enough. My focus was to make a revision to get the leakage as low as possible and to see if that was the limitation of the test, but also make sure that no mistakes were made in the assembly.

Don’t blame me for not trusting other people in debugging. In these situations I don’t trust anything (not even myself…) that I can’t prove, so I had to make a new sample to eliminate every other possibility. I also ditched the LCR meter and brought the big guns: my frequency response analyser is more than capable to give us a clear idea about the leakage-frequency dependency.

As Archimedes had his “eureka!” (“Εύρηκα” in Greek ) moment, I had mine while setting up the equipment testing! I asked myself: “How did I shorted the secondary winding?”. And my answer was: “Bending those 30mm wires you can see in Figure 1”.

Look at Figure 2. That’s the difference in leakage measured using different lengths of shorting wire at the secondary transformer pins.  

Figure 2. Difference in leakage inductance for 2 shorting wire lengths

There is a 8.32-5.72 = 2.6uH difference between the two measurements. Let’s prove this! Figure 3. is showing leakage model of an n:1 transformer.

Figure 3. Leakage model of an n:1 transformer

The measured leakage inductance shorting the secondary and taking a measurement on the primary side is: 

Where:

  • Llkg is the total primary reflected leakage inductance of the secondary (and the primary leakage) – also called lumped inductance.
  •  Llkp is the primary leakage inductance.
  •  LMAG  is the magnetizing inductance.
  • n is the turns ratio of the transformer.

We can simplify (1) with negligible error, noticing the fact that the magnetizing inductance LMAG is 50-60 times bigger than Llkg  , then:

In (2) the effect of different lengths of the shorting wire (Llks) result in different Llkg, since the effect of these inductances is magnified n2  = 72 = 49 times. For the 60mm shorting wire:

For the 8mm shorting wire:

Subtracting equations (4), (3):

Which gives us:

The round copper wire with an OD of 0.7mm has an inductance of 1nH/mm.

Less than 2% error in our analysis!

What about testing the transformer in the circuit?

As you might have guessed already, when I modified the leads to make sure the secondary pins were soldered directly to the board, everything was working ok, as seen in Figure 4! Extra leakage inductance on the primary side is in the order of 50-100nH because of the wires. Compared to the 5.7uH of the actual transformer inductance that’s an extra leakage ind. of less than 2% (see equation (2)).

Figure 4. Soldering the test transformer secondary pins directly onto the board

Summary and Conclusion

Flying leads on the secondary side when we are talking about a stepdown transformer, as is the case usually with flybacks, can actually “kill” you!

In our case study, just 52mm of extra wire leads of ~52nH of inductance added a 2.6uH inductance looking at the primary side. In flybacks were a leakage goal of 5uH of leakage is reasonable, to minimize the losses on RC snubbers across the primary winding, 2.6uΗ of inductance is a big deal!

Although, if that was a step-up transformer, then the extra inductance appearing at the primary would be close to nothing. In Table 3 you can see a summary of problematic cases. 

Table 3. Problematic cases with parasitic inductances-capacitances
Source: Frenetic

Related Posts

Inductors

Heating of Power Inductors in Switching Regulators

6.12.2023
6
Capacitors

Digital WE Days 2023 Virtual Conference Celebrates Record Participation

5.12.2023
8
Market & Supply Chain

November 2023 ECIA NA Electronic Components Sales Sentiment Setback in Attempted Recovery

4.12.2023
19

Upcoming Events

Dec 6
11:00 - 12:00 CET

Miniaturization, mechatronics, microvia: SLIM.flex PCB

Dec 6
11:00 - 12:00 MST

DigiKey Webinar on Strategic Procurement for 2024

Dec 11
December 11 @ 12:00 - December 14 @ 14:00 EST

Pre Cap Visual Inspection per Mil-Std-883 (TM 2017)

View Calendar

Popular Posts

  • What is a Dielectric Constant of Plastic Materials ?

    4 shares
    Share 4 Tweet 0
  • Understanding High-Precision Resistor Temperature Coefficient of Resistance

    0 shares
    Share 0 Tweet 0
  • Ripple Current and its Effects on the Performance of Capacitors

    3 shares
    Share 3 Tweet 0
  • Filter Poles and Zeros Explained

    0 shares
    Share 0 Tweet 0
  • Why Low ESR Matters in Capacitor Design

    0 shares
    Share 0 Tweet 0
  • Leakage Current Characteristics of Capacitors

    0 shares
    Share 0 Tweet 0
  • Inductors and RF Chokes Basics

    0 shares
    Share 0 Tweet 0
  • Capacitor Losses (ESR, IMP, DF, Q), Series or Parallel Eq. Circuit ?

    0 shares
    Share 0 Tweet 0
  • Filter Q Factor Explained

    0 shares
    Share 0 Tweet 0
  • How to Choose the Right Inductor for DC-DC Buck Applications

    0 shares
    Share 0 Tweet 0

Newsletter Subscription

 

Archive

2023
2022
2021
2020
2019
2018
2017

Symposium

Passive Components Networking Symposium

Passives e-Learning

Knowledge Blog

  • Home
  • Privacy Policy
  • EPCI Membership & Advertisement
  • About

© EPCI - Premium Passive Components Educational and Information Site

No Result
View All Result
  • Home
  • News
  • Video
  • Knowledge Blog
  • Preferred Suppliers
  • Events

© EPCI - Premium Passive Components Educational and Information Site

This website uses cookies. By continuing to use this website you are giving consent to cookies being used. Visit our Privacy and Cookie Policy.