650 amp 28VDC generator/Load Bank question

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Nefarious Mind

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Buffalo, NY
Hello all,

Let me begin by giving some background on my situation:

I work for a company that manufactures and tests large diesel engines, many of which produce 750-1200hp, and we are installing a new dyno room ( a room to test and measure engine performance ). A portion of the test includes a load test. The generator on this motor is a DC generator that produces 650 amps at 28VDC. We stress test the generator/motor by applying a load via a load bank. We are looking to utilize our existing load bank for both dyno rooms. I'm looking for a switching solution that will allow us to switch from dyno room #1 to dyno room #2.

Conceptually I'm looking for a 3 position switching ability: Dyno 1/OFF/Dyno 2. The issue I'm running into is the amperage capacity of various switches. Most do not accommodate 650A. It is also important to know that we don't actually test at that amperage very often. Generally speaking we run it at 50 amps and 200 amps of load. Lastly,because we test at various loads we have 10 quantity #10 wires coming from the load bank to a copper bus bar that connects to the generator. So we need run 10ct #10 wires to each of the dyno rooms... just something to keep in the back of your mind.

Oh and as always lets be budget friendly... otherwise we would have just bought a second load bank and control panel.

Thanks for reading.
 
You need a manual transfer switch, but an 800 amp manual transfer switch will probably cost $5,000 to $6,000.
 
I have used siemens railroad contactors for this type of thing. they are not cheap. but you only have to switch 1 wire for DC.

I looked it up. The PN I last used was SIEMENS 14-193-100-587 1250A DC CONTACTOR, 125VDC COIL

I don't even know if they sell them anymore as it has been a while. I think the guys in the shop had to use a forklift to set them in place because they are moderately heavy.
 
It would not be a bad idea to use an actual rated transfer switch, as suggested, since cross connecting Dyno #1 to an active or inactive Dyno #2, even with the load bank in parallel, could cause damage.
If it were not for that, two contactors with a manual switch that would energize at most one of them would do the job.
If the changeovers were infrequent you could just use a bus bar link that you could swing to one side or the other.
 
I'm going to suggest something out of the box here: a solid-state switch. What you're trying to do is a total piece of cake to accomplish with MOSFETs. As long as the maximum peak voltage can never exceed 150V, you could do it with eight of these: http://www.digikey.com/product-detail/en/ixys/IXFK360N15T2/IXFK360N15T2-ND/2217433 The total parts cost would be about $250 to achieve the A - OFF - B selection you want with 650A continuous capacity. The complete device would fit in the palm of your hand and be controlled by a simple toggle switch. The challenge here is that this is custom electronics work, not regular electrical wiring. It's a REALLY simple project for someone who knows how to do it, but you'd need to find an electronics geek (EE or hobbyist) to put it together. You could probably hire someone to figure this out for way less money than purchasing and installing a dedicated electromechanical switch rated for this kind of DC current.
 
160707-1533 EDT

Something does not compute. How, do you stress test a 1200 HP engine with a 25 HP load? For loading engines of this size you need a hydraulic load or something similar.
Then you need big outdoor heat sink to dissipate the heat.

.
 
gar said:
160707-1533 EDT

Something does not compute. How, do you stress test a 1200 HP engine with a 25 HP load? For loading engines of this size you need a hydraulic load or something similar.
Then you need big outdoor heat sink to dissipate the heat.

.
Click to expand...

The engine itself is connected to a dynamometer which is basically a water brake, but the load bank is for the 28VDC/650A generator that is attached to the motor. We want to simulate an electrical load for the generator on this particular motor.
 
gar said:
160707-1533 EDT

Something does not compute. How, do you stress test a 1200 HP engine with a 25 HP load? For loading engines of this size you need a hydraulic load or something similar.
Then you need big outdoor heat sink to dissipate the heat.

.
Click to expand...

good catch 650 x 28 / 746 = 25 HP
should not take a 1000 HP prime mover ll
 
Nefarious Mind said:
The engine itself is connected to a dynamometer which is basically a water brake, but the load bank is for the 28VDC/650A generator that is attached to the motor. We want to simulate an electrical load for the generator on this particular motor.
Click to expand...

so the generator is the engines dynamo?
charging batteries, engine control power, lighting etc?
 
Ingenieur said:
so the generator is the engines dynamo?
charging batteries, engine control power, lighting etc?
Click to expand...

Yes, this particular motor will be going into M88 and M60 military vehicles. The generator will be powering things such as lighting, turret, lift gate controls etc. Hence why part of the testing involves putting various loads on the generator while simultaneously dynoing the motor.
 
As this is a test facility is a change over switch really necessary? The test beds I’ve worked on used bolted links to select the various combinations required.

It’s not as if “unskilled persons” will operate the equipment, or at least I hope not.
 
Tony S said:
As this is a test facility is a change over switch really necessary? The test beds I’ve worked on used bolted links to select the various combinations required.

It’s not as if “unskilled persons” will operate the equipment, or at least I hope not.
Click to expand...

Unfortunately "skilled" doesn't always apply to absentmindedness, carelessness, unaware, and above all stupidity. Sometimes you have to think for those who can't think for themselves. Mostly because you will be the one held liable/accountable for not making it safe enough.

Luckily, I may have convinced the bean counters to spend a little more money and go with a second load bank, due to several factors including: comparative cost to build a change over switch vs. buying a new load bank, obvious safety concerns, feasibility, and down time from sharing a load bank ( only one motor can be tested at a time, whereas separate load banks allow for the utilization of both dyno rooms at the same time).
 
Nefarious Mind said:
Unfortunately "skilled" doesn't always apply to absentmindedness, carelessness, unaware, and above all stupidity. Sometimes you have to think for those who can't think for themselves. Mostly because you will be the one held liable/accountable for not making it safe enough.

Luckily, I may have convinced the bean counters to spend a little more money and go with a second load bank, due to several factors including: comparative cost to build a change over switch vs. buying a new load bank, obvious safety concerns, feasibility, and down time from sharing a load bank ( only one motor can be tested at a time, whereas separate load banks allow for the utilization of both dyno rooms at the same time).
Click to expand...
i think you arrived at a good solution
 
Nefarious Mind said:
Unfortunately "skilled" doesn't always apply to absentmindedness, carelessness, unaware, and above all stupidity. Sometimes you have to think for those who can't think for themselves. Mostly because you will be the one held liable/accountable for not making it safe enough.

Luckily, I may have convinced the bean counters to spend a little more money and go with a second load bank, due to several factors including: comparative cost to build a change over switch vs. buying a new load bank, obvious safety concerns, feasibility, and down time from sharing a load bank ( only one motor can be tested at a time, whereas separate load banks allow for the utilization of both dyno rooms at the same time).
Click to expand...

I wonder why engineers hate accountants?

I’ve resorted to subterfuge to get the equipment I needed. By the time the bill arrives on the bean counters desk it’s too late, it’s in and working and they have to get the cheque book out.
 
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