Why 32V?

[Ron Stauffer]

I have been curious why the early wind turbines were 32V. Since I work with DC in solar, the nominal system voltages are 12, 24 and 48. Newer DC wind turbines have followed suit. I understand that higher DC voltages allow smaller wire to be used when conducting current over long runs. At first, I thought 32V was the open circuit voltage. But then after looking at the schematic of the 32V Jacobs post and seeing 16 - 2 volt battery cells decided 32V was the nominal system voltage. So the open circuit voltage of a 32V Jacobs is probably in the 55 - 65 volt range?

With 2 volt cells for battery storage, they can put in series in any number for varying nominal system voltages. So why 32V? My guess would be that was the nominal voltage of the loads that it was powering - namely the radio electronics required that? Was that same voltage used for lighting? Please enlighten!

Ron Stauffer
Montrose CO

[Wayne]

Good question1 Hopefully answer will be forth coming.

[jacobs]

Line loss is too great with 12 volts, 24 volts was uncommon, 32 volts was what the railroads was using so 32 volt light bulbs were common. So why did the railroads use 32 volts?

[Ron Stauffer]

The site Smoktak had the same question asked. The replies were interesting.

https://www.smokstak.com/forum/showthread.php?t=14974

It does appear to have been driven by the RR using it. There is reference to the RR using 32 and 64. It was also posed there why did the RR use 32? Reasons given 32V were less dangerous being under 50V and high enough to keep wire size down but small enough to not be cost prohibitive for the battery bank.

I chuckled on reading that < 50V wasnt dangerous. Anyone ever lay a wrench across a 12V car battery? When we used to have to series and parallel many 6V batteries to get a lot of storage in 24V battery banks, we made special wrenches short and non conductive because shorting a 1500# battery bank with a wrench was very dangerous. Short circuit current on a battery bank is higher than most DC welders. Less than 50V is safer at the load side but has significant safety issues in the battery bank.

It was interesting reading about the RR cars that had a generator driven while moving to charge batteries so there was lights in the car at a train stop

Ron Stauffer
Montrose CO

[Wind Charger Mike]

I like the answer that 32V was chosen as a compromise be wire gauge and battery bank size. Also, our body's electrical impedance is high enough to prevent 32V DC from being lethal...in most situations. The 32V standard may have originated with Charles Kettering, the master mind behind the Delco Light Plants. Why 32V specifically? I suspect someone, maybe Kettering did an elaborate calculation with the range of variables that spit out 32 as the magic number and then convinced everyone else to use it. It must have been a convincing sell as 32V was widely used and accepted.

[Bootsy]

I was told that so many people were scared of 110 ,because it could kill you or your children! So the salesman
would say 40 volt dc was the danger area of dc so you could sleep with ease at 32 volt. No idea if this is true.

[Ron Stauffer]

There is a lot of debate over which is more deadly AC or DC and what voltage is deadly. Current is actually what kills. The National Electric Code was introduced in 1897 yes 1897. I dont know how far back it goes but they have recognized low voltage applications with separate regulations. Low voltage is considered anything under 50 volts AC or DC. Door bells, security systems, fire alarm systems, low voltage lighting, solar and small wind turbines are examples. Solar and small wind are getting in to the gray area of low voltage tho. Some solar charge controllers can handle 600 VDC to charge a 48V nominal system. And some small wind turbines produce 3 phase AC that feeds a converter to charge a 48VDC battery bank.

So what is the open circuit voltage of a 32 Jacobs?

Ron

[jacobs]

My 110 volt Jake will go over 200 volts open circuit so using the same ratio calculates to over 60 volts open circuit on a 32 volt generator.

[windmillerman]

The generator itself has 43 volts max on a tag attached to it....

[jacobs]

Many have used 32 volt Jakes to charge 48 volt batteries. Not ideal due to excessive current draw by the field coils but possible.