RJQMAN

I recently read where some people consider hybrids unsafe because of the danger of electrocution in an accident. The battery is most obviously DC, which should pose no danger. But after reading the article, I am curious - in s hybrid such as the 250H, is the DC voltage converted to alternating current for the motors? Or do the electric motor or motors run on DC?

herbvdh

In an accident there are safeties which will shut down the electric should it ever be damaged. I am pretty sure the motor is AC.

DDS62

Good question RJQMAN. I would guess that the motors are DC. I know of no advantage that could be realized by adding an AC converter in the battery circuitry and incorporating an AC motor. Perhaps the elimination of brushes?? Or perhaps for safety considerations?? I have heard many electricians describe the danger of DC current using the shop talk " DC don't let go!" Meaning that if you grab a live wire with DC current your hand will tend to grab it even harder whereas grabbing an AC live wire will only result in loss of control of your muscles allowing your body to pull away from the danger.

RJQMAN

I have been shocked by AC 110v at 60 hz United States line current. I had an all-metal power drill and was assembling a swing set - I was shirtless due to the heat, and sweating as well. I tucked the drill under my arm and plugged it in - I immediately got a severe shock, and I could not move my arm to release the drill or move my hands to unplug it. I really tried. Mentally I knew what was happening, but I could not move. I was told later that I fell to the ground, but I do not remember falling - I just found myself on the ground. Fortunately a neighbor that was helping me quickly unplugged the cord from the wall - probably saved my life. This was a long time ago.

I remember the Edison/Westinghouse stories when Edison was trying to prove that DC was safer, and so I thought DC would probably be fine. But I checked on the web tonight, and I read that the earlier poster is correct - it is hard or impossible to 'let go' under severe DC current shock - and since I know from experience, that it is hard or impossible to 'let go' under AC shock it sounds like the risk, whatever the risk is, would be the same either way. From what I read tonight, it takes more current to hurt you with DC, but no doubt either would be equally lethal in a car if you were to get a serious shock, due to the amount of current required to power an automotive drive motor.

I wonder if hybrid and/or all-electric cars have a 'ground fault' mechanism to prevent shock in the event of an accident. I have never read anything about this before one way or the other. Does anyone know? Just curious.

herbvdh

Yes it does have ground faults.

TheAirman

There are 2 motor generators on the HS. Both are 650 volt AC. The main battery is 245 volts DC. It almost stands to reason that somewhere in the system is a static inverter to convert the DC to AC to operate the motors. Most aircraft use that type of system to power their emergency AC bus. They use the main ships DC battery and a static inverter to convert the DC to AC to run emergency AC powered pumps.

Motor 1 in the HS is a generator to resupply the battery, the engine starter and something to do with the transmission.

Motor 2 drives the front wheels and recharges the batteries by regenerative braking, and is 141 horsepower.

So, the 2 AC in the HS motors are converting their AC power back to DC most probably by the means of a transformer rectifier unit somewhere in the system.

TheAirman

It's not the volts that gets you, it's the amps.

Even though it's 245 volts, the HS is just as safe as a regular 12 volt DC automobile. But in either case, I wouldn't want to drop my 9/16" wrench across the battery terminals!!!

herbvdh

The volts will not get you but what you do when you get HIT does you in. ie: Where do you land when you jump back instinctively?

I know a man wearing a gold bracelet on his wrist wiring up two 12 Volt 17 Amp hour batteries in series for a 24 Volt pack. Without realizing it he had his bracelet on a terminal while he ratcheted the other terminal tight the wrench hit his bracelet and melted it.

TheAirman

Oops. I bet he wears a PERMANENT bracelet now!!!

TheAirman

Here is a picture of the inverter and the part numbers. Don't worry, it's expensive.

rajeev6

Growing up in India I got zapped by 225 volts several times - first one when I was 7 or 8 and I was stuck to it. But later on, every time something triggered instinctively and I was able to unhook myself from the source.
I also remember getting minor shocks even on telephone lines which I think used to run on 40V DC.

I do have to say that I admire creative thinking on part of some people to come up with ideas that hybrids are bad because they can electrocute you! Truly innovative!

ntran18

iTrader: (27)

I 2nd that. This is also the like the Hindenburg argument against hydrogen cars. Of course, gasoline isn't as combustible as hydrogen.