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There's an episode in The Green Mile movie where the death row servicemen rehearse the upcoming execution that is done using an electric chair. One of them says (quoted from here):

Roll on one. [pause] "Roll on one" means I turn the generator up full. The lights go brighter in half the prison.

he says that and indeed ceiling lights in the building go brighter.

Which implies that the electric chair requires a generator that produces suitable voltage and also adds extra power required to sustain the peak power consumption of the chair. This part makes sense.

But the "lights go brighter" part implies that the generator is somehow connected to the mains in the prison. This makes no sense to me - connecting a high-voltage (more than a kilovolt) generator to 110 volts mains would cause electrical problems and would likely not give any advantage.

I couldn't find any evidence of such setups - electric chair powered by a generator connected in any way to the mains of the building. Do such setups exist?

Jamiec
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sharptooth
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    I don't see a contradiction here. I imagine the generator produces 110V and there is a transformer between the mains and the electric chair. – Jader Dias Jul 21 '11 at 11:47
  • @Jader Dias: Well, that's possible, but why would the lights go brighter then? – sharptooth Jul 21 '11 at 11:49
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    you already answered that. The generator is connected to the mains. The transformer draws energy from the mains. – Jader Dias Jul 21 '11 at 11:55
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    @Jader Dias: Assuming the 110 volts generator is connected to 110 volts mains the voltage should remain 110 volts, shouldn't it? If it remains the same the lights should not go brighter. – sharptooth Jul 21 '11 at 12:00
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    not if the voltages are slightly different, it never happened to you that a power hungry electrical appliance in your house diminished the lights when on? That's because consumption subtracted a few Volts from the mains. The opposite can happen when you have a generator. – Jader Dias Jul 21 '11 at 12:19
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    It could make sense to connect the generator to the mains: because apart from being used in electrocutions, the generator would also be used for backup power (to the prison lights) if the mains electricity failed (in the same way that generators are also present in hospitals and in telephone exchanges). – ChrisW Jul 21 '11 at 12:21
  • why not hook it up to the mains? It has to be hooked up somewhere, and if not to the same as the rest of the facility they'd have to bring in a special powerline just for that one appliance that gets used maybe once a month. Hardly worth the investment. – jwenting Jul 21 '11 at 13:41
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    @jwenting: Well, I'm not an electrician, but if I needed to power some appliance like that from a generator I'd put that generator as close to the appliance as possible and not need long wires. – sharptooth Jul 21 '11 at 13:47
  • @Adam: Find a source, make it an answer. – Lennart Regebro Jul 22 '11 at 08:30
  • @sharptooth we're not talking extension cords here, obviously, but a high capacity cable running from the same point in the building where the rest of the electrical power comes in to the generator/capacitor. – jwenting Jul 22 '11 at 08:31
  • @jwenting: If you want to add a generator and pass power from that generator to some dedicated appliance through the building mains you have to make all the wires along that path much thicker, that's not cheap either. – sharptooth Jul 22 '11 at 08:33
  • Was thinking of having the generator being hooked up to the capacitors for the chair primarilly, but having a secondary capability as a backup generator for the security systems in case there's a power failure. – jwenting Jul 22 '11 at 13:07
  • @Jader Dias - a vacuum doesn't dim the lights because it draws "a few Volts from the mains", it dims the lights because it draws extra *current* - amps - from the circuit – warren Jul 25 '11 at 14:18
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    @warren You're right, and so am I. One thing leads to another. – Jader Dias Jul 25 '11 at 14:22
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    It could be to prevent the generator from tripping due to the sudden change in load. Powering the building would provide a base load to smooth out the sudden spike. – KonradG Sep 20 '11 at 01:53
  • @JaderDias, If the electricity in your home is connected correctly, meaning in parallel, then you can't draw voltage, but you do draw current. That is why your lights dim, and this can also be a reason for lights in a prison to be more powerful, because the generator puts more current to the system. The power of an Incandescent light bulb (which is a resistor) is IV, so increasing or decreasing the current changes the power output of the light bulb. It's not one thing leads to the other. – SIMEL May 25 '13 at 01:24
  • In the movie, the generator is connected to the lights. There is no suggestion that 'mains' are involved anywhere. Since (a) the movie is set in the past, and (b) the prison is set in a rural area, it is entirely normal to have a building powered by a generator, rather than connected to the mains. – Excel VBA problem with Find Aug 14 '14 at 11:58
  • @frednurk: What do they mean by "turn the generator up full" then? – sharptooth Aug 14 '14 at 12:43
  • For example, from the [Annual Report of the Board of Prison Commissioners](http://www.forgottenbooks.com/download_pdf/Annual_Report_of_the_Board_of_Prison_Commissioners_of_Massachusetts_1000723667.pdf): "Under a resolve of 1908, and by direction of the chairman,there has been added to the electric lighting plant a 25 horse-power gasolene engine and a 16 kilowatt generator,which will enable us to light the whole institution with electricity there by avoiding the danger of fire from the kerosene lamps." Here is some information about another generator shed :[New Zealand](http://bickler.co.nz/clo – Excel VBA problem with Find Aug 15 '14 at 01:39
  • My impression (as an electrical engineer, reading industry journals and the like) has been that this is all over the map. Early setups used a generator, because they needed AC and the mains (if they even existed) were DC. Several executions were botched due to insufficient power supply (apparently assisted by a poor understanding of the concept of electrocution), so there was more emphasis on overpowering the problem, one way or the other. – Daniel R Hicks May 14 '18 at 12:19
  • The Green Mile is fiction and should not be taken as representative of how real executions by electrocution are done. – Carlo Felicione May 14 '18 at 14:26
  • In the novel A Lesson Before Dying (but drawn from a real case), Louisiana's portable electric chair is brought to the parish (county) jail. The portable chair is in a museum and can be verified on Wikipedia. In the novel, it's being powered by a generator brought on the same truck. Seems plausible but I couldn't find that detail anywhere else. – Andrew Lazarus May 14 '18 at 23:40
  • @AndrewLazurus: That isn't any more definitive than the original claim, so it is just a repeat of the claim, rather than an answer. – Oddthinking May 15 '18 at 04:22

2 Answers2

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In this article from 1976 regarding Texas reactivating their electric chair after the death penalty moratorium imposed by the US Supreme Court was lifted, the article specifically mentions the generators used for the electric power to the chair.

This gizmodo story about Ted Bundy's execution also mentions the diesel generators used to power Florida's electric chair.

Why a generator is used when utility power is more than sufficient is another matter. This may be to avoid the possibility of a power failure and a botched execution.

The 'dimming of the lights' seen in this video of a last Bundy interview, when Florida was testing the electric chair for him, was actually the prison switching over from utility power to the backup generators.

tj1000
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OK, did more Googling.

Louisiana used a portable electric chair, nicknamed Gruesome Gertie, which is now in a prison museum. The chair was brought in a panel van to the parish (county) jail where the condemned man was imprisoned. The chair was powered by a generator running from the van engine. [Source: "Old Sparky: The Electric Chair and the History of the Death Penalty"]

Setting up the Louisiana generator is a scene in the novel "A Lesson Before Dying", which was inspired by an actual Louisiana execution.

phoog
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Andrew Lazarus
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  • Why was the condemned imprisoned in a panel van? – phoog May 17 '18 at 02:20
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    No, the _chair_ and _generator_ were brought to the jail in a van. The condemned man was in a cell. The novel has a scene for setting the chair up, but I forget exactly where—I think it's inside with the wires run through a window—that probably was taken from the actual event modeled. – Andrew Lazarus May 17 '18 at 02:45
  • Did they also use the generator and the van for supplying popcorn for the execution spectators? Seems like dual purpose food/generator use would be a great business opportunity. – PoloHoleSet Aug 20 '18 at 15:47