FAQ
TL;DR: To get 400 Hz from 220 V, one path is “use a rectifier then a dc/ac inverter”; note AT/ATX switchers run ~30–70 kHz. [Elektroda, Mark Majewski, post #21662238]
Why it matters: Students often ask how to make safe, realistic 115/28/26 V 400 Hz supplies for labs and avionics-style loads.
Quick Facts
- Sizing example: 28 V × 25 A ≈ 700 W; pick ~850 W amp/transformer to cover losses. [Elektroda, JAWED MATEEN, post #21662245]
- Audio amp + sine generator + step‑up transformer works if the transformer is rated for 400 Hz. [Elektroda, Kevin Parmenter, post #21662240]
- Rectify 220 V to ≈300 V DC, then invert to 400 Hz; AT/ATX typically switch at 30–70 kHz. [Elektroda, Mark Majewski, post #21662238]
- One supply for 115/28/26 V depends on exact current per output; specify each rail. [Elektroda, JAWED MATEEN, post #21662247]
- Reversing a 220 V→30 V transformer can step up when driven by an audio amp; verify 400 Hz operation. [Elektroda, JAWED MATEEN, post #21662241]
How do I convert 220 V 50 Hz to 400 Hz AC for a school project?
Two common routes: 1) rectify 220 V to roughly 300 V DC, then feed a 400 Hz inverter; or 2) generate a 400 Hz sine and amplify it. The rectifier–inverter path mirrors how many supplies work, but you must design the inverter stage and output filtering carefully for a clean waveform. Define your load current and whether you need a sine wave before choosing. [Elektroda, Mark Majewski, post #21662238]
What’s the simplest way to get 115 V/400 Hz in a lab?
Use a sine‑wave oscillator into a robust audio power amplifier, then step up with a transformer rated for 400 Hz. This approach is hands‑on, uses off‑the‑shelf parts, and yields a sinusoidal output. As one expert put it, “make sure the transformer can deal with 400 Hz.” [Elektroda, Kevin Parmenter, post #21662240]
Can I drive a transformer in reverse to step up voltage at 400 Hz?
Yes. One contributor tested a standard 220 V→30 V, 50 Hz transformer wired in reverse, driven by an audio amplifier. Adjust the input amplitude to set your output voltage. Verify the core and winding temperature at 400 Hz and under load to avoid overheating. [Elektroda, JAWED MATEEN, post #21662241]
How much power do I need for 28 V at 25 A?
You need about 700 W at the load (28 V × 25 A). Size the amplifier and transformer around 850 W to cover conversion and thermal losses with headroom. This margin helps avoid clipping and overheating during continuous operation or start‑up surges. [Elektroda, JAWED MATEEN, post #21662245]
How do I generate a clean 400 Hz sine wave?
Use a sine generator (function generator or oscillator circuit) set to 400 Hz, feed an audio power amplifier, then a transformer. This chain preserves the sine shape if you avoid amplifier clipping and keep the transformer within its frequency rating. [Elektroda, Kevin Parmenter, post #21662240]
Can I modify a PC AT/ATX PSU to output 400 Hz?
Not practically. AT/ATX supplies switch around 30–70 kHz and are optimized for DC outputs, not 400 Hz AC. Modifying them for a stable 400 Hz sine is complex and unreliable for student builds. Use a purpose‑built inverter or the audio‑amp method instead. [Elektroda, Mark Majewski, post #21662238]
Do I need a pure sine output for 400 Hz loads?
Many 400 Hz applications expect a sine wave. One responder asked explicitly whether your load requires a sinusoid. If your instruments mimic 400 Hz mains, choose a sine output; the audio‑amp approach produces it naturally. Clarify this before designing. [Elektroda, Mark Majewski, post #21662238]
How can I supply 115 V, 28 V, and 26 V from one system?
It depends on current per rail. A helper requested exact current for 115/28/26 V to propose a single‑supply plan. With defined currents, you can choose transformer taps or separate secondaries and size the amplifier accordingly. Provide those numbers first. [Elektroda, JAWED MATEEN, post #21662247]
Is there a quick 3‑step build plan I can follow?
- Set a 400 Hz sine source and feed an audio power amplifier.
- Connect the amplifier to a suitable transformer wired to step up/down as needed.
- Measure output voltage under load and adjust input amplitude; confirm the transformer handles 400 Hz. [Elektroda, JAWED MATEEN, post #21662241]
What are common pitfalls when driving transformers at 400 Hz?
Using a transformer not rated for 400 Hz can cause excess heating or saturation at load. Also, an undersized audio amp will clip, distorting the sine and raising losses. As one expert warned, “make sure the transformer can deal with 400 Hz.” [Elektroda, Kevin Parmenter, post #21662240]
What details should I share to get accurate help?
State total power and the exact current for each voltage rail (115 V, 28 V, 26 V). Helpers asked specifically for power/current before proposing a unified design. Include whether the output must be sinusoidal and any duty cycle expectations. [Elektroda, JAWED MATEEN, post #21662247]
Is rectifying 220 V to ~300 V DC a valid first step?
Yes. Rectifying and filtering 220 V AC yields roughly 300 V DC, which can feed a dedicated 400 Hz inverter stage. This method matches how contributors suggested approaching a 400 Hz source when designing beyond the audio‑amp route. [Elektroda, Mark Majewski, post #21662238]
