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| Has everyone ever "cheated" https://www.rypn.org/forums/viewtopic.php?f=1&t=40812 |
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| Author: | RCD [ Fri Jun 16, 2017 11:13 am ] |
| Post subject: | Has everyone ever "cheated" |
That's doing some research into some high voltage High amperage solid-state electronics and seems quite simple to build a traction controller for a trolley using fairly inexpensive parts. I.e. a 555 timer circuit driving a really big transistor. Has anyone ever attempted to do this? |
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| Author: | Dave [ Fri Jun 16, 2017 11:51 am ] |
| Post subject: | Re: Has everyone ever "cheated" |
Gomaco uses electronic controls. I'm uncertain just what. We as an industry do need a source for what looks like old time controllers no matter what is inside the case. There are a lot of chicken coops out there. |
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| Author: | wilkinsd [ Fri Jun 16, 2017 1:55 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
While I'm not saying it's impossible, what I discovered is that while a lot of components are rated for DC, as the voltage increases, the rated amperage it can take decreases. Old streetcar electrics were robust for a reason, making and breaking connections at 600v while pulling some serious amperage. Before I employed any modern solution, I'd thoroughly investigate the amperage issue. |
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| Author: | dinwitty [ Fri Jun 16, 2017 10:35 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
There are plenty of high current and voltage transistors, thyristors, silicon controlled diodes whatever else like even DCC control. Someone want to get experimental, but they better know what they are doing before digging into it. A wrong component in high joltage in experimental mode could be an experience... |
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| Author: | dinwitty [ Fri Jun 16, 2017 10:42 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
The early systems played games between series/parallel/resistors to get various speeds. Because a railcar can coast very well, you can notch in/out at speed. Constant current is not required |
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| Author: | EDM [ Sat Jun 17, 2017 12:25 am ] |
| Post subject: | Re: Has everyone ever "cheated" |
For a museum operation? No need to re-invent the wheel- |
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| Author: | Dave [ Sat Jun 17, 2017 7:18 am ] |
| Post subject: | Re: Has everyone ever "cheated" |
Except we're out of old stock wheels and nobody is making more, while we need more wheels at prices we can afford. |
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| Author: | fkrock [ Sat Jun 17, 2017 12:59 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
Something you need to keep in mind with DC traction motors is when you turn off the power, the motor coils can kick back as much as 10,000 volts or higher. So you need to have some serious arc suppression devices in the circuit. Many solid state devices that may operate with high current up to 2,000 volts DC will not tolerate a 10,000 volt spike even though it may last for only a few microseconds. K-type controllers contain many arc suppression devices. They contain insulating boxes that will prevent an arc from spreading if one develops. Another problem is that a high voltage spike may create a path of ionized air that will conduct 600 volt power. The old motor controllers were very simple devices. They contain plain castings and parts fabricated from metal. Some of the parts are still available as new-old stock from the original manufacturers if you know where to look. General Electric and Westinghouse bought parts from small manufacturers. A competent machinist should be able to fabricate a copy of a K-type controller. The wood usually is maple and the controller top is cast iron. |
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| Author: | Dave [ Sat Jun 17, 2017 6:31 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
OK, so what if we went with off the shelf relays mounted perhaps under the car or in another convenient location and used a multiposition switch inside the controller case replica with a big replica handle to use lower control voltage to actuate the relays which would actually switch resistors in and out of the 600VDC circuit? An added advantage is it would be fairly easy to MU. A kicking coil could ameliorate the spikes..... |
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| Author: | robertmacdowell [ Sat Jun 17, 2017 6:38 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
You're basically talking about a slightly upsized Zilla controller. Those are already a thing. If you want to use AC traction motors, then you want the EV flux vector drives made for AC induction motors. They are readily available for voltages up to 400VDC and up. It shouldn't be a problem to find one for a commn off the shelf 480V 3-phase motor, and that would want 600VDC input. It goes without saying that any electronic control would retain a physical main contactor, electromechanically controlled by the controller so that regardless of what the silicon chooses to do, off is off. For a single car, there is also something to be said for making reverse mechanical, as otherwise the silicon gets a lot more complicated. @dinwitty "played games"... that's how controllers work. That is the entire point of a K, HB/HL, GE equivalent, PCC, and even cam control cars, not to mention the transitions in any diesel larger than a GE 80-ton. Basically everything uses those. This is all lost motion, the controller is the easy part to make. It's the trucks! |
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| Author: | NYCRRson [ Sat Jun 17, 2017 6:38 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
As a Electrical Engineer with formal degrees (BSEE and MSEE from the 1980's) I would caution you about "cheating" when dealing with electricity. Besides the surge currents mentioned by others you need to carefully consider properly isolating the HV parts of a circuit from the rest of the circuit. Just the ripple voltage on a 600 volt line is enough to take out any "logic" circuits. And, the DOA logic circuit could leave the motor fully energized. And, the leakage current from the HV side if parts are not properly rated can be fatal. And, you need a proper enclosure to contain any arc-flash when testing your circuit. It can be done, but there is a reason getting an EE degree takes a while. Best case your setup "smokes" the first time you power it up, worst case you "smoke". "Hey, this is a brand new circuit, it's too young to smoke." The old electro-mechanical controllers are incredibly robust and simple to copy. The size of the devices provides most of the needed insulation and arc suppression. Just be careful, also make sure any test equipment used is properly rated, most DIY multi-meters are barely rated for 300 Volts. Any test equipment needs to be able to handle the max voltage, surge volts above that and a safety factor (2x-3x). So you would need multi-meters in the 2500 Volt range. These exist, but are "spensive". I've been working with "lectricty" for 40 years and I still turn my face away when flipping a 110V circuit breaker, just in case...... Good luck and be very careful, Everybody's been studying Electricity for Years, Nobody knows how the heck it works.... Cheers, Kevin. |
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| Author: | TrainDetainer [ Sat Jun 17, 2017 10:00 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
What Kevin said. And as for a low voltage switch controller and power contactors under the floor - The cost of all those contactors for 600V DC at 1000+Amps would make recreating new controllers as originals the much cheaper choice. If you're running 1200V or up, even more so. |
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| Author: | RCD [ Mon Jun 19, 2017 10:34 am ] |
| Post subject: | Re: Has everyone ever "cheated" |
For back current you just use a big diode wired in parallel with the motor. Just modifying this circuit should seem to work  I would connect C1, pins 4, 8, and R2 to a separate low voltage Supply being driven by a DC DC step down circuit and the mosfet and D3 would be heavily uprated. |
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| Author: | Randy Gustafson [ Mon Jun 19, 2017 12:06 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
The Savannah streetcar is a rather one-off cheat, for different reasons - the gensets under the noses are conventional AC gensets for yachts, and the car also was intended to be operational for 600 VDC overhead wire if Savannah ever got it down the road, so the motors are DC. So in the middle it's not batteries - it's ultracapacitors. rectifiers, and Allen-Bradley controllers. While the car has had wheel/axle problems, the electronics end has been pretty stable from the get-go using programmable controllers and custom software, although it was certainly an untested application. This was not an amateur job, either, the entire system was designed by EMS out of Altoona - they are traction motor rebuilders for Juniata shop, so they are no stranger to heavy electrical. http://www.emsmotors.net/ Nothing was custom-built on that car, it was all an exercise of using off-the-shelf components and integrating them. As much of a cheat as humanly possible, and meet ADA transit requirements like the door interlocks, etc. The downside of using 'old school' controllers is that somebody has to be really familiar with how to set and properly maintain them - the Memphis system and the controller flashovers and fires are what brought that to a standstill. There's truth on both sides here, it's not an absolute answer. https://www.memphisflyer.com/NewsBlog/a ... management |
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| Author: | crij [ Mon Jun 19, 2017 2:06 pm ] |
| Post subject: | Re: Has everyone ever "cheated" |
I know I am sliding on the edge of my knowledge base, but why reinvent the second generation wheel. There are plenty of Electric Locomotives, Subway, and Trolley-pole buses that use the same voltage combinations that (as far as I have heard) heritage trolleys use. To save yourself money you don't need current generation equipment, last or previous generation should be good enough salvage for the light duty work the equipment will see. Currently Amtrak is retiring the AEM-7 (IIRC) Swedish Meatballs/Toasters and the HHP-8 locomotives. These currently run on multiple voltages down the Northeast Corridor, I forget what it is south of NYC, but east of New York City they run on 700VAC 3rd rail and 22K VAC catenary. I am sure there are other railroad & railway parts from the 1950-1970 that could be retrofitted into hidden spaces and replica enclosures. Just an idea, Rich C. |
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