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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Mike Sokol on November 16, 2017, 04:30:52 pm

Title: 5 Megawatt Load Bank
Post by: Mike Sokol on November 16, 2017, 04:30:52 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
Title: Re: 5 Megawatt Load Bank
Post by: TJ (Tom) Cornish on November 16, 2017, 05:21:55 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
It's interesting the assumptions that different industries make - e.g. "high voltage" in the electronics industry would be 120V while "low voltage" in the electrical trade would be 120V, and 7KV might be "low voltage" in the distribution trade.

I wonder what impedance this thing is and what input voltage it is designed for - whatever "medium voltage" is.
Title: Re: 5 Megawatt Load Bank
Post by: Tim McCulloch on November 16, 2017, 05:34:39 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

Mrs Sokol may not be keen on giving up her parking spot...
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol on November 16, 2017, 05:51:13 pm
It's interesting the assumptions that different industries make - e.g. "high voltage" in the electronics industry would be 120V while "low voltage" in the electrical trade would be 120V, and 7KV might be "low voltage" in the distribution trade.

I'm pretty sure in the power industry that anything below 600 volts is considered "low voltage". I took a 600 volt shock hand-to-hand once, and it was terrifying. I'm thinking that 600 to at least 11,000 volts is considered "medium voltage" since that's what is commonly found on the street power lines. The high voltage rating goes upwards to at least 500,000 volts around here and even 1 million volts in some high-tension lines. That's a whole lotta volts... 
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol on November 16, 2017, 05:53:02 pm
Mrs Sokol may not be keen on giving up her parking spot...

She already kicked my Hammond B3 and Leslie out of the living room years ago.  ;)
Title: Re: 5 Megawatt Load Bank
Post by: David Buckley on November 17, 2017, 08:10:24 am
On a warm day that will be a thoroughly unpleasant thing to be anywhere near to.  Just a couple of hundred KVA of load bank turns a cold day to hot beach, so 5MW, faaaaark...

A note that it is a MV unit, so there will be a fairly chunky transformer in that container as well as the fan heater.
Title: Re: 5 Megawatt Load Bank
Post by: Kevin Graf on November 17, 2017, 08:39:16 am
At the radio station transmitter site, we had a 50,000 Watt @ 100 MHz dummy load. It was just a little larger than a coffee can and the heating element was the size of a cigar. But it also had a car radiator, fan and water pump,
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol on November 17, 2017, 08:44:19 am
On a warm day that will be a thoroughly unpleasant thing to be anywhere near to.  Just a couple of hundred KVA of load bank turns a cold day to hot beach, so 5MW, faaaaark...
So you're saying I could roast marshmallows over it like a campfire? That's another win in the plus column...  ;) BTW: Just how many watts does a campfire output?
Title: Re: 5 Megawatt Load Bank
Post by: John Roberts {JR} on November 17, 2017, 09:28:28 am
I'm pretty sure in the power industry that anything below 600 volts is considered "low voltage". I took a 600 volt shock hand-to-hand once, and it was terrifying. I'm thinking that 600 to at least 11,000 volts is considered "medium voltage" since that's what is commonly found on the street power lines. The high voltage rating goes upwards to at least 500,000 volts around here and even 1 million volts in some high-tension lines. That's a whole lotta volts...
On that scale, static would only be high medium voltage.  8)

JR
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol on November 17, 2017, 12:46:17 pm
On that scale, static would only be high medium voltage.  8)

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
Title: Re: 5 Megawatt Load Bank
Post by: Steve Alves on November 17, 2017, 02:14:01 pm
So you're saying I could roast marshmallows over it like a campfire? That's another win in the plus column...  ;) BTW: Just how many watts does a campfire output?

The average campfire (not bonfire) produces 4,700,000 BTU. Using an online calculator (1 BTU/hr = 0.29307107 W) that shows as 1,377,434.029 Watts.
Title: Re: 5 Megawatt Load Bank
Post by: Tim McCulloch on November 17, 2017, 02:47:23 pm
The average campfire (not bonfire) produces 4,700,000 BTU. Using an online calculator (1 BTU/hr = 0.29307107 W) that shows as 1,377,434.029 Watts.

So Mike would have the very expensive equal (think of his electricity bill) to about 4 campfires.

Burn wood, Mike.
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol on November 17, 2017, 02:51:37 pm
The average campfire (not bonfire) produces 4,700,000 BTU. Using an online calculator (1 BTU/hr = 0.29307107 W) that shows as 1,377,434.029 Watts.

I think you're confusing BTU Hours with BTUs, so at the very least you need to divide your total watt output by 60, maybe more. I'm pretty sure a campfire doesn't put out more than 1.3 megawatts of heat, but maybe it does 23kW. Can somebody check the equation and math?
Title: Re: 5 Megawatt Load Bank
Post by: Art Welter on November 17, 2017, 03:17:06 pm
I think you're confusing BTU Hours with BTUs, so at the very least you need to divide your total watt output by 60, maybe more. I'm pretty sure a campfire doesn't put out more than 1.3 megawatts of heat, but maybe it does 23kW. Can somebody check the equation and math?
Wood has anywhere from about 8000 to 9700 BTU per pound, depending on resin content. If we go for the highest BTU at 9700 x a 10 pound campfire, the total BTU output would be around 97,000, with the output spread over a time period depending on how the fire was made and tended. Lets say a fast burn, 1 hr=97,000 BTU =28KW.
Title: Re: 5 Megawatt Load Bank
Post by: Stephen Swaffer on November 17, 2017, 06:35:55 pm
So, do you have large enough feeders to hook it up?
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol on November 17, 2017, 08:01:27 pm
So, do you have large enough feeders to hook it up?
I've got a 2/0, 3-phase, 120/208 feeder, so in Y mode that's 200 amps x 120 volts x 3 legs = 72,000 watts. That's only 1.44% of 5 MW. But in Delta mode that's 200 amps x 208 volts x 3 legs = 124,800 watts. That's still only 2.4% of 5 MW if I'm doing this right. I don't think that would even warm up this load bank up enough to spin the fans. But I can dream, can't I?  ;D
Title: Re: 5 Megawatt Load Bank
Post by: Stephen Swaffer on November 17, 2017, 09:18:39 pm
Of course, the point of a load bank is to test the cable to see if they warm up under load...

Tap into 480 and you can do a tiny bit better-get the right medium voltage feed and you can make some headway-though arcing might pose a problem.
Title: Re: 5 Megawatt Load Bank
Post by: David Buckley on November 19, 2017, 06:07:47 pm
So you're saying I could roast marshmallows over it like a campfire?

You can fry stuff up on a frypan on top of a 1K parcan.  You can torch stuff with a few well-aimed sharpies.  A 200KW fan heater will carbonize your marshmallows in a blink of an eye.   Assuming (a) the marshmallows could be persuaded to stay on the sticks, because you are talking about a significant amount of airflow here,  and (b) as long as the sticks were a many feet long, otherwise your body will also be in the jetstream, and will also be toasted to a crisp.

Load banks are mean pieces of engineering.
Title: Re: 5 Megawatt Load Bank
Post by: Erik Jerde on November 19, 2017, 09:44:59 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

And the dielectric strength of air is 33Kv/cm so in those upper ranges things can get exciting real fast when you're not careful.
Title: Re: 5 Megawatt Load Bank
Post by: David Buckley on November 19, 2017, 10:19:17 pm
So next time you see a "DANGER HIGH VOLTAGE" sign on a door, chances are, it isn't really.
Title: Re: 5 Megawatt Load Bank
Post by: Chris Hindle 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.
Title: Re: 5 Megawatt Load Bank
Post by: Nathan Riddle 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 (https://en.wikipedia.org/wiki/Order_of_magnitude)) then:

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

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

 :D
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol on November 21, 2017, 09:23:02 am
Following the convention (Orders of Magnitude (https://en.wikipedia.org/wiki/Order_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
Title: Re: 5 Megawatt Load Bank
Post by: Jonathan Johnson 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.)
Title: Re: 5 Megawatt Load Bank
Post by: Mac Kerr 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 (https://www.amazon.com/SawStop-PCS31230-TGP252-Professional-Assembly-Extension/dp/B005HPWE5W)!

Mac
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol 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... ;)
Title: Re: 5 Megawatt Load Bank
Post by: TJ (Tom) Cornish 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.
Title: Re: 5 Megawatt Load Bank
Post by: Mike Sokol 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?
Title: Re: 5 Megawatt Load Bank
Post by: TJ (Tom) Cornish 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.
Title: Re: 5 Megawatt Load Bank
Post by: Geert Friedhof on December 19, 2017, 09:47:49 am
Or just  read the specs on this page:

http://fettingpower.com/current-inventory/load-banks/5mw-avtron-cr229i-load-bank/
Title: Re: 5 Megawatt Load Bank
Post by: Matt Errend on December 28, 2017, 04:34:33 pm
I've got a 2/0, 3-phase, 120/208 feeder, so in Y mode that's 200 amps x 120 volts x 3 legs = 72,000 watts. That's only 1.44% of 5 MW. But in Delta mode that's 200 amps x 208 volts x 3 legs = 124,800 watts. That's still only 2.4% of 5 MW if I'm doing this right. I don't think that would even warm up this load bank up enough to spin the fans. But I can dream, can't I?  ;D

Not to be a stickler here, but 3 legs at 208 is the same amount of power no matter if you're running delta or wye. The formula for three phase power is Volts (line to line) x Amps x  √3

For your 120/208 200A feeder, your available real power is 72kVA no matter how you slice it.