Created Date: July 11,2010

Created by: KPrice

dieseltwitch, theoretically, the DC voltage would be sq. rt. 2 times the RMS voltage (ignoring ripple), for example, 1.4 x 240V = 336V for RMS voltage of 240V. Then to get the voltage at your load, subtract (amp x resistance) voltage drop.

It sounds like you are driving a generator, then rectifying to get DC. You also could drive a DC generator directly for DC.

We have used Ohio Magnetics equipment for many years. We have used other companies also, but we 've used Ohio the most.

Here is a link to their rectifiers.

http://www.ohiomagnetics.com/hddcps.htm

They also carry DC generators.

You are right - lots of amps.

Hope this helps.

Created Date: July 11,2010

Created by: dieseltwitch

Yeah.

In theory Im working out the number, parts and design to build a Seriies Hybrid truck (small suv)

In therory it will work as fallowing;

Diesel Generator spins AC generator (size TBD) This output is rectified down to DC, The DC is fed into both a battery back and the drive inverters (2x One forward one aft ( the battery pack minimizes genset waste power and short cycling, and will allow for a given range of travel with out even turning the generator on)

Basically this is the same way a train work but on a smaller scale. I 've been able to calculate the HP and Tq requirements for the vehicle i would put it in. and thus far a 55- 65 Kw Generator would be able to carry the entire drive load. how ever by using the battery back I can always make sure the generator is running at max eff.

As for not running a DC generator (only found 30kw) with an AC Generator I can use it as a back up generator for my hope, camping (oversized i know)

Its just kind of a fun little idea i have been toying with. I know it really doesn't fit this forum but people here seam to know a lot so i thought i would ask. I work in the solar thermal industry and love electronics. so this kind of came up by a force of nature

Any thoughts?

Created Date: July 11,2010

Created by: KPrice

Wow, sounds like quite a project. Thanks for the info. We had done a lot of work on rail cranes. The rail cranes had a Diesel Engine that ran DC generators that ran DC traction motors. One gen was for the power gen for the motors, another gen for the power gen field. And another gen for the lifting magnet. There was 4-speeds forward and 4-speeds reverse switched by a big drum switch. The drum switch switched resistors in the field circuits. It was very interesting work. Caution: Hi amp DC equipment is expensive. Have fun.

Created Date: September 24,2010

Created by: doug6949

We had done a lot of work on rail cranes. The rail cranes had a Diesel Engine that ran DC generators that ran DC traction motors. One gen was for the power gen for the motors, another gen for the power gen field. And another gen for the lifting magnet. There was 4-speeds forward and 4-speeds reverse switched by a big drum switch. The drum switch switched resistors in the field circuits.

This is essentially how the propulsion systems worked on early rail transit vehicles. For example, Chicago's transit cars had four series wound 90HP DC motors, one on each axle. The system ran on 600 VDC.

A drum sequencer switched the motors from series to series parallel and finally to parallel as the speed increased. Resistor banks were also switched in and out to provide a total of about eight speeds.

The drum sequencer was about nine feet long and two feet wide/tall. Contact failures were frequent, grand, and glorious. I saw more than one transit car with a large hole in the side where something blew apart.

KPrice is correct. Hi amp DC switch gear is extremely expensive. It is also getting hard to find. The design of this equipment is mostly black art that has been lost over the years.

We tried to get GE to modify a switch box for Chicago back in 1991. After several months of stalling us they finally admitted all the engineers who had done this work were either retired or long dead.

This is reason enough to stay away from DC propulsion.

Created Date: September 24,2010

Created by: dieseltwitch

Thanks guys but this project has taken a major backseat after I found out just how much the parts will cost me....

My plan was to use two ac drives, one would act as a rectifier/starter for the gender and the other would be put right next to the first and drive the two traction motors, each drive was 159kW and liquid cooled, they have some other awesome features. The motors were also awesome, 9 " deep, 15 " diam and could spin an impressive 350 ft-lbs each, were rated for 60kw but could take 150kw each so long as I could keep them cool, they are liquid cooled also! The final major part was a dc to dc converter used to step down the 480VDC bus to 12 VDC for use with normal car parts, so i contacted the mfg and after about two weeks this is what I get back:

Drives(each) 39 '800 USD

Motors(each) 16 '900 USD

BSC623-12V: 22 '000 USD

That's a total of $118,500 for two motors, two drives and a dc/dc..... In two words.

F-That! ( I know that a hyphen I just didn't want to get into trouble)

If any one is interested in r&ding somthing on our own please contact me!! Lol

Created Date: October 03,2010

Created by: DetroitSound

The path is never easy for a pioneer. I had given some thought to that concept, but I was considering doing experimental work with essentially modified industrial drives, about 20hp.

Remember that a DC motor gives its highest torque at a dead standstill. An AC drive can't but it can be geared appropriately.

I want to build a hybrid, useful for freeway use. I would think 20hp should be adequate, with a 5-10 hp motor to drive a generator. That was going to be a starting point (with my typical seat-of-the-pants engineering). But using a motor to provide breakaway torque, the actual horsepower requirement of an engine to drive it should be modest.

That's my thinking...

Created Date: October 04,2010

Created by: dieseltwitch

Its good to see I'm not the only one thinking along these lines.

I thought long and hard about what i wanted to use, AC or DC. DC motors are cheaper but in my mind less reliable and harder to do any thing more then move forward. When DC motors fail they can fail locked wide open (and by dc motors i mean the motors and any control gear that goes with) while they can provided max torque Im not looking for just starting torque. I need high tq at full speed also. I also want regen, more for breaking then power generation (very very hard to do with DC, i 've seen it done and it looks messy!) AC motors provide what i think is the best option for me. While the one supplier i found is way over priced I'm some one sure i can either find another one or even make my own some day.

You are also correct on that minimal HP is required in most cases. 20 HP is good for most small cars on flat city roads.... I don't live in the city and I need something better then a car. I need to carry a load from time to time, tools, parts. I also have to climb more then one 6 - 7% mtn pass on a regular basses.

I came up with a formula that I use to calculate the amount of HP needed to keep a car/truck rolling at any given speed. its not based on frontal area or hard to figure out stuff like that. if you like I can send it to you. I also can use it to figure out how much HP is need to keep a car/truck rolling up a given slope. I did this on my jetta and found about 14 HP is need to maintain 75 on a flat road. I forget how much is needed for a 6% grade but you get the idea. I 've done some math also on figuring the tq need acc for different tire sizes and gearing.