1.5 MW Cummins Diesel Genset - Page 2 - PeachParts Mercedes-Benz Forum

vstech · #16 12-13-2017, 08:02 AM

Quote:

Originally Posted by jay_bob

The ends have lovers to draw combustion and cooling air in one end and expel hot air from the radiator out the other end.

Unless you actually have scantily clad men and women ventilating for you...

TimFreeh · #17 12-13-2017, 10:28 AM

Quote:

Originally Posted by barry12345

Interesting post. Never knew those large gen sets burnt so much fuel.

1.5 megawatts is a lot of power, as I recall that kind of load would power something like 1,000 average sized homes.

Given the work it's performing I don't think the fuel usage is at all excessive.

Diseasel300 · #18 12-13-2017, 12:44 PM

Quote:

Originally Posted by Mxfrank

Some data centers use rotating UPS's, rather than battery systems. These are high speed inertial flywheels that couple incoming power to yet another generator. A rotating UPS doesn't provide as much run time as a battery system, but it's significantly lighter. Otherwise battery weight would constrain the design of a large data center.

Just out of curiosity...how do you phase match the output of the generator in multiple generator installations or where the generator runs in parallel with utility power?

The old rotating UPS's are slowly going away. The most common place we still see them installed is at telephone exchanges, many of which have been running since the 40s and 50s.

Phase matching can be done manually or automatically. Modern systems have a master panel that controls load sharing and automatic synchronizing of the various systems. Once the tie breaker is closed, the synchronization is fixed, they can no longer drift out of synchronization until the breaker is opened.

jay_bob · #19 12-13-2017, 03:43 PM

There is actually a modern rotary UPS. It uses the similar ac to dc to ac conversion scheme like a static (one that uses batteries) UPS. Except instead of storing the energy in batteries it spins up a rotating mass in a vacuum chamber.

Active Power :: Critical Power Solutions is one manufacturer of these.

Phase matching is done with a device that compares the voltage from the generator with the voltage on the bus. You have to have 3 things aligned, the frequency, the voltage, and the phase angle (the sine waves have to match each other in time).

There are 2 methods for synchronization. The first is passive, you just let the generator free-run on its own internal 60 Hz clock, and eventually the sine wave from the utility and the generator will momentarily align. It’s just like sitting behind another car at a red light and watching their turn signal and your turn signal blinking. Since they are both driven by their own time base, with slightly different timing, they will drift between appearing completely synchronized and completely out of sync. There is a special protective relay that compares the two waveforms and issues a signal to proceed with the transfer at exactly the right moment.

The second method is active synchronization. Using the utility voltage as a reference, you create an error signal to the generator controls to cause the generator to adjust its voltage and speed to bring its sine wave exactly in time with the utility and hold it there. You confirm that they are in sync with the same protective relay and then command the transfer to occur. This is more complex but produces a better transfer (less disturbance in the power system).

This is an example of a device that does the comparison and generates the reference signals to the generator speed and voltage controls: http://www.woodward.com/spmd21.aspx

This is also how you parallel multiple generators on a bus. You get the first one started and use it as the master source. Then as multiple generators come up to speed, they are regulated into synchronism and commanded to close in.

Once you are paralleled, the speed reference becomes the percent load, and you can cause a generator to contribute anywhere from 0 to 100% of its available capacity to the bus by altering the fuel quantity. There are interconnections between each generator’s controllers to allow each generator to be an equal contributor to the total load. Also the control scheme looks at the total load demand and the available generator capacity, and can start up or shut off generators as needed to make the best match to the requirements for the load. When bringing the generator onto or off the bus, by modulating the fuel, is how the load is gently applied or removed from the generator.

97 SL320 · #20 12-13-2017, 04:34 PM

Quote:

Originally Posted by jay_bob

Cool, what kind of facility do you manage, if you're allowed to say?

It is a manufacturing facility. Laser cutting table , plasma cutter on a robot, CNC mills , lathes , saws , 500 ton mechanical stamping press from the 20's , hydraulic stamping presses, press brakes, 30 HP rotary screw air compressor + 50 HP that turns on if the 30 goes down. Also assembly area and a electrical test transformer that is 15 ft high and 8 ft dia. I take care of any equipment that isn't physical building / water / nat gas / IT .

Others speced out the generator ( used ) but neglected to calculate the 50 GPH @ full load it needs, they through the "day" tank + a 275 G supply we use for grounds equipment would be enough. . .

With a 18 hr work day, we need 2 days of fuel to make a gen worth the effort. This is 1,800 gal so round up to 2,000. The ended up getting a 500 G tank, so far that has been holding out.

Generac and probably others by now make a gen that starts on diesel then transfers to mostly nat gas by feeding fuel through the air intake. Think controlled run away. This is what we should have got since we have a gas well on site.

Our transfer system / startup is manual since we don't have or need a UPS. We do have a 20,000 W Kohler nat gas fueled gen with auto transfer for the servers.

Mxfrank · #21 12-13-2017, 05:35 PM

Rotating gensets have been used for generations, and yes, very popular with the old Bells. In my era, the flywheels were iron, but nowadays they are made of carbon fiber layups. CF is much lighter, which helps with floor loading. But they can spin up to higher RPM, so the stored energy is comparable. I think the reactive load is the same in either case, but I don’t ever recall that being a consideration.

I had an interest in phase matching, because I can’t get my head around “selling” excess rooftop solar to the grid. Clearly it can’t be matched as you would a diesel genset, because you aren’t adjusting physical rpm. You’d have to sense phase on the same line used for output. I think that no matter how fast your switchgear, you’d end up with phase error. That would mean that a lot of expensive solar power would end up as waste heat. But Im an old guy, and I have a lot of quaint notions.

jay_bob · #22 12-13-2017, 06:21 PM

The rotating converters were used prior to the advent of electrical rectification.
In the telephone central office, they take the commercial power and turn it into -48 V dc. In the old days it was a rotary converter. Of course the modern equivalent is the rectifier.

Fun fact, they would take the 60 Hz commercial power, convert to -48 V dc with a rotary converter, and float that across the batteries. The vast majority of the switching equipment as well as the subscriber lines and trunks came from the -48 V dc. Any other voltage that was needed, such as the 90 V, 20 Hz ringing voltage, came from another dc powered rotary converter. This way everything ran off the batteries. Of course now all that is solid state rectifiers and inverters.

The modern flywheel UPSs do have a carbon fiber rotor. A co worker of mine was in the room when one had a catastrophic failure. He thought he was a dead man. Funny he was just telling me that story last night.

Solar is another animal. The residential grade solar inverters cannot output unless the utility is present, per NEC and UL requirements. Most likely for the issue you described. This upset a lot of people in the hurricane zones this fall who lost their power but their solar system survived. They found out that they could not use the solar system power to run their house unless the utility was available.

jay_bob · #23 12-13-2017, 07:03 PM

Here’s another one I found, 3 x 2 MW Cats
https://youtu.be/J7oADIcqb1Y

I would check this one quick, this looks like a data center, chances are if the data center owner finds out this is on the web it will get yanked and these Cat guys will be permanently banned from that customer’s sites and probably looking for new jobs.

Hence why I never can share any pics or specific details about what I do.

Mxfrank · #24 12-13-2017, 07:32 PM

Quote:

Originally Posted by jay_bob

The rotating converters were used prior to the advent of electrical rectification.
In the telephone central office, they take the commercial power and turn it into -48 V dc. In the old days it was a rotary converter. Of course the modern equivalent is the rectifier..

Once upon a time, IBM mainframe shops commonly used rotary gensets to convert utility power to 415hz. The "UPS" carry time was a free benefit.