Low frequency coil problem

[Giuseppe]

I wanted to ask you if using a 0.6 ohm 0.6mH coil at frequencies lower than 6 HZ with duty+ 14% square wave with ZK-PP2K generator turns off completely. Furthermore, at frequencies such as 14Hz 14%duty+ always square wave the power supply always goes into protection when the coil is activated but the PP2K remains on. How to solve these problems?
I power everything with a 12V 3A power supply protected against over current
Thank you

[david]

Hi,
At such low frequencies the inductive reactance of your 600uH inductor is much less than its DC resistance so you will go in to current limit of your supply.
Why would you want to use such low frequency PWM?

Cheers,
David

[Giuseppe]

To limit this, can I put a low-value resistor in series with the coil?

[rick.curl]

To limit this, can I put a low-value resistor in series with the coil?

Yes you can, but you'll just be burning up energy in the resistor instead of putting it into the coil.
Can you lower the voltage of the supply instead?  Maybe down to 1 or 2 volts.

-Rick

[Giuseppe]

Thanks for the replies, I'll try and let you know

[charliecoutas]

Such low frequency PWM is interesting. Several years ago, when I worked for a local company, we used to hire out one of our 2KW variable frequency power supplies to a company who brought them back with evidence of sea water in/on them. They reluctantly explained to me that they were dragging inductive coils along the seabed while varying the frequency in a PWM pattern. I think they were looking for certain, presumably valuable, metals. Perhaps this was a precursor to materials used in modern batteries?

But their frequencies were from 60 to 400Hz.

Charlie

[SeanG_65]

Charlie, I know of an as yet unlocated wreck 1/2 mile off the Dorset coast which has around £75 million in gold. The problem is trifold.

1) The damn stuff moves around with the tides(a bar of gold ONLY weighs the amount of water it displaces when under water)

2) Gold has a notoriously short magnetic response time

3) By now, the gold will be spread over a huge area (it was payment bound for the US for war materiel but the ship was torpedoed just off the Dorset coast and went down). Salvage was attempted at the time, but the area was repeatedly mined by U-Boats at night and as fast as the RN swept them, they were replaced. In the end the risk was deemed too great nad after the war, it was noticed, no one could remember where the wreck was!

[charliecoutas]

Has anybody got a boat Sean and I could borrow?

[Giuseppe]

A lot of money £75 million