Choke question

[Smokebreak]

My choke came in today for my current build, Hammond 155H - 5H, 50mA, 400VDC max. I'm using the 6V6 Plexi PS, and it has a 5K5W between SS rectifier/res cap and the choke, but I'm still concerned about the choke's VDC rating. I missed that when I ordered it. PT is Edcor 600VCT, I'm unfamiliar with how chokes are spec'd, so I'm wondering if this 400VDC rating is something I need to be concerned with. I also figure that the 50mA rating is fine, since it's not seeing plate current?

[JazzGuitarGimp]

My choke came in today for my current build, Hammond 155H - 5H, 50mA, 400VDC max. I'm using the 6V6 Plexi PS, and it has a 5K5W between SS rectifier/res cap and the choke, but I'm still concerned about the choke's VDC rating. I missed that when I ordered it. PT is Edcor 600VCT, I'm unfamiliar with how chokes are spec'd, so I'm wondering if this 400VDC rating is something I need to be concerned with. I also figure that the 50mA rating is fine, since it's not seeing plate current?

I am pretty certain the 400VDC rating is from both leads to GND, in other words, the frame of the choke since it is sitting at GND potential when you screw it down to the chassis. As long as both the input wire and the output wire are at or below 400VDC, you'll have no issues. Does this rating usually err to the side of safety? Probably. But at some voltage above 400V, the insulation will break down and an arc (and carbon track) will result.

[pdf64]

I'm running a Hammond 400V choke at about 450V without problems.
It was cheap and I was ordering some other Hammond transformers.
It's for me rather than a customer and the B+ is fused etc, so I figured 'what's the worst that could happen?'.
Pete

[Smokebreak]

Thanks guys.
I'm still a bit confused....probably from a lack of understanding of how a choke is mechanically constructed...

ok so frame of a choke is at ground potential, bolted to the chassis. Say the insulation on the leads breaks down...what exactly happens? The wire would arc to the frame? Thus shorting B+ to ground? I guess I don't see how the leads and the frame are connected, if that's the case

[Phil_S]

A choke is a coil of wire wound on a core. Basically it is a transformer with one winding. So, it is a bit like a big resistor, but with a good measure of inductance added. Unlike a resistor, it's "value" varies according the the amount of current flowing through it. (There is all sorts of math I don't fully comprehend, so I'm going to skip over it!) The inductive property serves to smooth out AC ripple.

It is a single coil of wire, each end connected to the B+ supply ladder. The frame is touching the metal laminations. Bolting the transformer to the chassis creates a ground for the lams and frame. In this respect, it is a bit like a capacitor in that coil is insulated from the lams. Bolting it to the chassis isn't really "ground" as we think of it in the circuit.

[JazzGuitarGimp]

Thanks guys.
I'm still a bit confused....probably from a lack of understanding of how a choke is mechanically constructed...

ok so frame of a choke is at ground potential, bolted to the chassis. Say the insulation on the leads breaks down...what exactly happens? The wire would arc to the frame? Thus shorting B+ to ground? I guess I don't see how the leads and the frame are connected, if that's the case

Yes, that is correct - in much the same way an OT arcs and shorts as a result of overvoltage from running the amp with no speaker load.