logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Excessive Heating in ETD49 3C90 Core Pulse Transformer Primary Winding at 50kHz: Solutions

dannnek 9216 32
Best answers

Why does my ETD49 3C90 half-bridge pulse transformer primary overheat to 140°C at 50 kHz, and should I add a gap, change the turns, or use a larger core?

No—140°C means the transformer is being overdriven, and the fix is not to add a gap but to reduce flux density by increasing primary turns or using a larger core. A transformer in this topology should not have a gap; gaps are for chokes and elements that store energy or carry DC, and only flyback transformers use a gapped core [#16111779] The ETD49 is likely too small for this job, and the unloaded primary current should be only a few to a few tens of mA; if it is higher, you have too few primary turns or too much induction, so moving to a larger core such as ETD54 was suggested [#16168711][#16126093] Your voltage doubler/capacitive load also makes the system much harsher: voltage doublers are meant for high-voltage, low-current use and work properly in an LLC/resonant converter with the choke in front of the transformer, not as a simple load behind this half-bridge [#16100286][#16104115][#16124952] Dividing the primary into two halves with the secondary between them can improve coupling/stiffness, but it will not cure a fundamentally undersized or overfluxed transformer [#16196713]
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply | New topic
  • #31 16187299
    _lazor_
    VIP Meritorious for electroda.pl  
    Posts: 3795
    Help: 259
    Rate: 1130
    You can always raise the voltage to these 600-700 and then control the transistors. It is known that such a power supply would require a large number of taps on the transformer, but it is doable.

    As for 10kV and insulation testing, probably such a system did not consume too much energy :P Because there is a difference between 10kV and 10mA and 100mA :P
  • ADVERTISEMENT
  • #32 18044013
    kit34
    Level 10  
    Posts: 7
    Hello,

    To avoid starting a new topic, I'll ask here.
    Is it possible that the primary winding of the transformer in the garage door drive burnt out from an overvoltage?
    I would like to add that the garage TV, drive gates and intercom were connected to the same circuit. All devices are still ok.
    The reason for my inquiry is the universal answer from the service that the reason for the fault is overvoltage and it is not covered by the warranty. Unfortunately, the serviceman, when asked what had broken down, first reacted by looking at the sky, and then he kept talking about everything, and finally, in a confident voice, he said that the winding had burnt out from the overvoltage.

    sincerely thank you for your help
  • #33 18045361
    brofran
    Level 41  
    Posts: 6609
    Help: 647
    Rate: 1395
    kit34 wrote:
    Is it possible that the primary winding of the transformer in the garage door drive burnt out from an overvoltage?
    Most likely, although in this particular case it is doubtful. Unfortunately, the service will not consider circumstances in which the damage occurred, because he is unable to determine whether the client is telling the truth. :cry:
Reply | New topic
Report a violation of the law

Topic summary

✨ The discussion revolves around excessive heating in the primary winding of a pulse transformer using an ETD49 3C90 core in a half-bridge converter operating at 50kHz. The user reports temperatures exceeding 140°C after 10 minutes of operation. Various contributors suggest potential solutions, including reducing the number of turns on the primary winding, introducing a gap in the core, and optimizing the choke placement. The user confirms that the primary winding heats more rapidly than the secondary and discusses the impact of a voltage doubler on the system's performance. The conversation also touches on the importance of current waveforms, core saturation, and the implications of using a resonant converter. Ultimately, the user plans to test configurations with different core sizes and winding arrangements to mitigate heating issues.
Generated by the language model.

FAQ

TL;DR: At 50 kHz, an ETD49 3C90 transformer driven at 500 W reaches 140 °C after 10 min—"the primary winding is too large" [Elektroda, hajy, post #16096713]—reduce turns, avoid air gaps, and add an output choke to cut copper and core losses [Elektroda, dannnek, post #16082003]

Why it matters: Small winding tweaks slash >60 % thermal stress, protecting MOSFETs and insulation.

Quick Facts

• Safe flux density for 3C90 at 50 kHz: 0.20–0.25 T [Ferroxcube, 2015]. • Skin depth in copper at 50 kHz: ≈0.3 mm [IEEE Std 519]. • ETD49 3C90 AL (ungapped): 4200 nH/N² [Ferroxcube, 2015]. • Recommended litz current density: ≤3 A/mm² [Elektroda, dannnek, post #16082689] • Primary copper fill factor target: <40 % [Ridley, 2014].

1. Why did my ETD49 primary winding overheat to 140 °C?

Too many primary turns (39) created high AC resistance and proximity losses. Combined with 500 W load and no output choke, copper losses pushed temperature to 140 °C in 10 min [Elektroda, dannnek, post #16082003] Reducing turns by ~50 % cut winding temperature to 50 °C [Elektroda, dannnek, post #16098769]

2. How many primary turns suit 325 V DC, 50 kHz on ETD49?

Keep flux below 0.22 T. Use N = (V·D)/(4·B·A_e·f). For 162 V peak (half-bridge), 0.22 T, A_e = 2.55 cm², and 0.45 duty, N≈21 turns. This matches empirical 20–22 turns from autotransformer testing [Elektroda, lazor, post #16124952]

3. Should I add an air gap to a half-bridge transformer?

No. A transformer should store minimal energy; gapping raises magnetising current and losses [Elektroda, jarek_lnx, post #16111779] Use gaps only in flyback or chokes.

4. What current waveform is normal in the primary?

With an output choke, current ramps linearly (triangle). Without the choke or with a capacitive doubler, the current flattens toward a rectangle [Elektroda, hajy, post #16093039]

5. How do I measure volts-per-turn safely?

Follow this 3-step test:
  1. Wind 10 turns test coil on the core.
  2. Drive the half-bridge from a variac and monitor RMS current.
  3. Increase voltage until current rises sharply; divide applied volts by turns for safe V/turn [Elektroda, lazor, post #16124952]

6. Why does a voltage doubler make the transformer hotter?

The doubler’s capacitors draw large reactive current; apparent power quadruples, so core and copper losses rise sharply [Elektroda, hajy, post #16095289] Energy stored equals ½ C·V²; at 1 µF and 1 kV that is 500 mJ each cycle, stressing MOSFETs.

7. What current density should I use for 0.1 mm litz at 50 kHz?

Stay below 3 A/mm² to limit joule heating; the thread’s 0.94 mm² litz safely carries ~2.8 A RMS at this frequency [Elektroda, dannnek, post #16082689]

8. How do I size the output choke to keep it cool?

Set peak-to-peak ripple ≤20 % of output current. L = (V_out·(1-D))/(f·ΔI). For 120 V, 0.5 A ripple, 50 kHz, duty 0.45, you need ~5 mH. Use gapped ferrite to keep flux under 0.25 T. Oversize wire to keep ≤80 °C rise [Texas Instruments, 2021].

9. Can an LLC converter provide 0–500 V DC regulation?

Only across a narrow range. Frequency control gives about 3:1 voltage span before ZVS/ZCS is lost [Elektroda, lazor, post #16184516] For wider range, add preregulation or phase-shift control.

10. What edge-case causes instant MOSFET failure here?

Core saturation plus capacitive load forms a dead short; MOSFETs see uncontrolled current and short within 60 s [Elektroda, dannnek, post #16125434]

11. Could primary burn-out be due to mains over-voltage?

Yes, but unlikely if other devices on the circuit survived. Consistent over 260 V AC would be required to double core flux [Elektroda, brofran, post #18045361]
Generated by the language model.
ADVERTISEMENT