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Author Topic: PWM Interference from Eltek 48 Volt 3000W Power Supply Fan  (Read 84 times)

K3SK

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de K3SK


I am in need of a schematic , or as a minimum the circuit layout for the cooling fan circuit in an Eltek Valere Flatpack2 48v3000w P/N 241119.905A HE. I am trying to eliminate noise created by the power supply's PWM circuit that controls the cooling fan.

I use these power supplies to power a couple solid state KW amplifiers. When first keyed down there is no issue. After a short time as the power supply load increases and the cooling fan in the supply speeds up I start hearing a low frequency buzzing/pulsing on my transmitted signals. I'm 99% sure the fan PWM circuit is my problem. When unkeying and the PS fan slows down, the noise disappears. I've added half a dozen ferrite beads on the DC supply lines to the amplifier that reduced the noise somewhat, but receiving stations still report to me that there is noise. One guy even described it a sounding like a helicopter flying outside my window. This noise is identical on all of these Eltek 3000 watt power supplies I've tried.
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W9IQ

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Re: PWM Interference from Eltek 48 Volt 3000W Power Supply Fan
« Reply #1 on: May 18, 2020, 02:58:37 PM »

You should consider calling an applications engineer Eltek Valere for assistance with the problem.

You said you put ferrite on the DC bus. Make certain you run the positive and negative leads through the same bead or toroid in order to avoid saturating the ferrite and reducing its effectiveness. Also use ferrite material appropriate for the frequencies involved. I would also suggest a ferrite regime on the fan leads themselves.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.
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