Burden
Burden turns up in 2 fields: electrotechnology, metallurgy. Here is what it means to the people in each one.
Burden in electrotechnology
Load connected to the secondary of an instrument transformer, stated in VA or ohms.
Burden is the total impedance placed across a CT or VT secondary by relays, meters and connecting leads, stated in volt-amperes at rated secondary current or voltage. A CT rated 15 VA at 5 A can drive 0.6 ohm and still hold its accuracy class. Long lead runs, especially with 5 A secondaries, eat into the burden and can push a protection CT into saturation during a fault.
"Lead run from the yard CTs to the relay room is 300 m, that's most of the burden on a 5 A secondary, go 1 A next time."
Burden in metallurgy
The solid mix of ore, fuel, and flux loaded into the top of a smelting furnace.
The burden is the carefully calculated recipe of raw materials fed into a blast furnace. It typically consists of iron ore, metallurgical coke, and limestone. The ratio, sizing, and distribution of the burden dictate the chemistry of the resulting pig iron and the efficiency of the gas flow rising through the furnace.
"The sulfur levels in the hot metal are creeping up, so we need to adjust the limestone in the burden."