A general rule for wheeled vehicles is the brakes should dissipate about what the engine can deliver. +/- a lot; but that general order of magnitude.
A Diesel-electric is usually a few thousand horsepower, say 2,000HP. 750 Watts in a Horse. So the brake resistors may be about 1,500,000 Watts.
After setting an OPT on fire when a dummy load resistor went open in a tube amp cranking out about 150 watts on 750 volts, I got these 500 watt 8 ohm resistors on Ebay for about $10 each....over 20 years ago.
Not purely non-inductive, but the measured inductance worked out to be less than a 1% error at 20 KHz, so they have been my test resistors of choice when pushing out anything over 100 watts.....and for most other tests too. In this test they were subjected to a strenuous 25 watt per channel workout with an UNSET test board.....No sweat.
In the next test I took the same UNSET board, drove the two channels out of phase, connected up the Mother of All OPT's, dialed back the idle current, and turned up the power supply. This was a mono single channel test, so only one load resistor was used. The power supply and drive signal was adjusted to produce about 250 watts of power output at the dull red glow point in the Mother of All Sweep Tubes. Pressing on toward 300 watts caused clipping which caused a blown resistor in the screen grid supply.
The end result will be something in the 500 WPC range using 6 of these tubes per channel. This one resistor ate 250 watts for several minutes. I did smell something hot, which turned out to be the cardboard shipping box that the resistors were laying on. Being that there are the biggest tubes and OPT's that I have, I don't think I will ever need bigger load resistors.
Not purely non-inductive, but the measured inductance worked out to be less than a 1% error at 20 KHz, so they have been my test resistors of choice when pushing out anything over 100 watts.....and for most other tests too. In this test they were subjected to a strenuous 25 watt per channel workout with an UNSET test board.....No sweat.
In the next test I took the same UNSET board, drove the two channels out of phase, connected up the Mother of All OPT's, dialed back the idle current, and turned up the power supply. This was a mono single channel test, so only one load resistor was used. The power supply and drive signal was adjusted to produce about 250 watts of power output at the dull red glow point in the Mother of All Sweep Tubes. Pressing on toward 300 watts caused clipping which caused a blown resistor in the screen grid supply.
The end result will be something in the 500 WPC range using 6 of these tubes per channel. This one resistor ate 250 watts for several minutes. I did smell something hot, which turned out to be the cardboard shipping box that the resistors were laying on. Being that there are the biggest tubes and OPT's that I have, I don't think I will ever need bigger load resistors.
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Maybe someone will use these ones from the dynamic braking of a T1 subway car
They should be good for a few kWFrom what I gathered in person, those spirals are basically the same as the coils on an electric stove... I'll bet they will glow under hard braking...
I have a few motor starters using those resistors..as a test load for hifi?.....overkill? Much?
(The motor is 1MW)
How about these nice Tyco? (I have a few dozen 4R0)
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The fact they are 1R 50W tells me they are supposed to handle 50A continuously even though the leads are like number 22 wire... Also a TO-220 package isn't great for more than about 20W Pd so I should have known. Still, the resistor was only asked for 4W Pd in the circuit, just the inrush was too much although it did work a few times.
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