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Author Topic: 5 Megawatt Load Bank  (Read 1976 times)

Chris Hindle

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Re: 5 Megawatt Load Bank
« Reply #20 on: November 20, 2017, 08:17:32 am »

So next time you see a "DANGER HIGH VOLTAGE" sign on a door, chances are, it isn't really.
Maybe not, but it will still kill you in a flash.
Don't take ANY voltage lightly.
Chris.
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Nathan Riddle

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Re: 5 Megawatt Load Bank
« Reply #21 on: November 20, 2017, 01:57:48 pm »

I just found the ANSI definitions. So 99.9 kV is considered "Medium" voltage. Holy crap...

Voltage classes: (ANSI C84.1-2016)

Low Voltage: 1000 volts or less

Medium Voltage: greater than 1000 volts and less than 100 kV

High Voltage: greater than 100 kV and equal to or less than 230 kV

Extra-High Voltage: greater than 230 kV but less than 1000 kV

Ultra-High Voltage: equal to or greater than 1000 kV

Following the convention (Orders of Magnitude) then:

Extra-Low Voltage: greater than 1mV and less than 1V

Ultra-Low Voltage: greater than 1uV and less than 1mV

 :D
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Mike Sokol

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Re: 5 Megawatt Load Bank
« Reply #22 on: November 21, 2017, 09:23:02 am »

Following the convention (Orders of Magnitude) then:

Extra-Low Voltage: greater than 1mV and less than 1V

Ultra-Low Voltage: greater than 1uV and less than 1mV

 :D

Are those dangerous voltages as well?  ;D
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Jonathan Johnson

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Re: 5 Megawatt Load Bank
« Reply #23 on: November 21, 2017, 05:07:03 pm »

I was looking around for a surplus load bank for some of my experiments and I came upon this semi-trailer version. Now the picture says 5 mW which I always thought a lower case "m" denoted milliwatts, but I'm pretty sure this is a 5 MegaWatt load bank as in 5 million or 5,000,000 watts. I don't know why, but I really want one of these... ;D

I've been looking at getting a table saw -- a stationary "cabinet" style saw, at least 3 HP. I don't have a lot of money to spare, so I'm looking at used saws. It seems that 3 phase saws come up on the C-list fairly often at pretty reasonable prices, but I don't have 3 phase power available. That's probably why they come up cheap -- hard to sell 3 phase machines.

(Well, I probably could put 3 phase power in if the utility didn't charge more than my annual salary to put in a transformer bank, plus charging me commercial rates -- the lines come right into the yard less than a hundred feet from my workshop.)

But then I realized that for the right deal, I could get a VFD (variable frequency drive) for a three-phase saw. More efficient than a rotary or solid state phase converter, and available for single phase supply. The VFD plus the 3-phase saw might end up costing less than a single phase saw.

Anyway, to bring this back to the original topic, the VFD supports the installation of a load bank for dynamic braking. Mike's load bank might be a wee bit of overkill, but hey, you could probably stop that saw nearly instantly with that kind of sink!

(Or maybe not.)
« Last Edit: November 21, 2017, 05:09:34 pm by Jonathan Johnson »
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Mac Kerr

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Re: 5 Megawatt Load Bank
« Reply #24 on: November 21, 2017, 06:09:15 pm »

Anyway, to bring this back to the original topic, the VFD supports the installation of a load bank for dynamic braking. Mike's load bank might be a wee bit of overkill, but hey, you could probably stop that saw nearly instantly with that kind of sink!

Or you could spend the really big bucks and get a SawStop!

Mac
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Mike Sokol

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Re: 5 Megawatt Load Bank
« Reply #25 on: November 21, 2017, 06:10:37 pm »

I've been looking at getting a table saw -- a stationary "cabinet" style saw, at least 3 HP. I don't have a lot of money to spare, so I'm looking at used saws. It seems that 3 phase saws come up on the C-list fairly often at pretty reasonable prices, but I don't have 3 phase power available. That's probably why they come up cheap -- hard to sell 3 phase machines.

(Well, I probably could put 3 phase power in if the utility didn't charge more than my annual salary to put in a transformer bank, plus charging me commercial rates -- the lines come right into the yard less than a hundred feet from my workshop.)

But then I realized that for the right deal, I could get a VFD (variable frequency drive) for a three-phase saw. More efficient than a rotary or solid state phase converter, and available for single phase supply. The VFD plus the 3-phase saw might end up costing less than a single phase saw.

Anyway, to bring this back to the original topic, the VFD supports the installation of a load bank for dynamic braking. Mike's load bank might be a wee bit of overkill, but hey, you could probably stop that saw nearly instantly with that kind of sink!

(Or maybe not.)

This is a great example of how to get a topic swerve back on point... ;)
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Mike Sokol
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TJ (Tom) Cornish

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Re: 5 Megawatt Load Bank
« Reply #26 on: November 21, 2017, 07:46:03 pm »


Anyway, to bring this back to the original topic, the VFD supports the installation of a load bank for dynamic braking. Mike's load bank might be a wee bit of overkill, but hey, you could probably stop that saw nearly instantly with that kind of sink!

(Or maybe not.)
if this load bank is designed for a couple thousand volts, it may have a fairly high impedance, meaning it might not work so well at 208 volts.
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Mike Sokol

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Re: 5 Megawatt Load Bank
« Reply #27 on: November 21, 2017, 08:00:39 pm »

if this load bank is designed for a couple thousand volts, it may have a fairly high impedance, meaning it might not work so well at 208 volts.

If we knew what voltage it was we could easily calculate the impedance for 5 megawatts of load. I gave that on a quiz today for my audio electronics students. So what voltage shall we assume it needs for the full 5MW?
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Mike Sokol
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TJ (Tom) Cornish

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Re: 5 Megawatt Load Bank
« Reply #28 on: November 21, 2017, 08:54:34 pm »

If we knew what voltage it was we could easily calculate the impedance for 5 megawatts of load. I gave that on a quiz today for my audio electronics students. So what voltage shall we assume it needs for the full 5MW?
Well, based on your chart, my calculations show 0.2Ω for 1001V, 20Ω for a 10KV voltage up to about 2000Ω for a 99KV input voltage.  A 2KΩ load won't be a great brake for your VFD at 240 volts - that's only about 30 watts.  If it's 0.2Ω, that would definitely be an effective brake.
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Geert Friedhof

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Re: 5 Megawatt Load Bank
« Reply #29 on: December 19, 2017, 09:47:49 am »

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