804B. I'm not able to get voltage to 480. Help.

[Harris101Ranch]

We bought a 804B last year to run a irrigation pivot, we needed to to run 480V it was doing 440v I replaced the voltage control rheostat this spring now it's only giving me 360 to 380 volts. Any recommendations? I am going to order a new voltage control rheostat are there any suggestions on where to get a good one?

 

[peapvp]

If you look at your Generator carefully then you will discover a nameplate like this one here:



the nameplate indicates that this particular model is rated for either
120/208 or 240/416

you can kiss the ground you are walking on that it ever got up to 440 in the first place.

To get to to 480 you will need to get a three phase step up transformer

 

[DieselAddict]

+1, its not a 480v generator. Its 416v.

 

[Harris101Ranch]

Yeah I have the same plate I guess now I'm just curious as to why it has a plate showing it can do 480. Or am I understanding it wrong?

 

[peapvp]

Yeah I have the same plate I guess now I'm just curious as to why it has a plate showing it can do 480. Or am I understanding it wrong?

The voltage adjust rate is the range the voltage adjust rheostat can adjust the output voltage in general.

Its 395 VAC on the low side and 480 VAC on top side. Both are the absolute maximum and minimum ratings of adjustable range.

When the A1 / A11 start to go bad, then the range indicated on name plate can no longer be achieved, resulting in preventive maintenance.

The rating is 416 VAC or 208 VAC, that is what the Generator Head is designed and built for.

Operating the Generator at any other Voltage then 208 VAC or 416 VAC can cause problems and premature equipment failure.

The A1 / A11 is the number one casualty, then the exciter coil assembly and its Diodes

Its up to the operator to make the judgement call and carry the responsibility when operating at extreme limits.

Because of the age and the aging of the components in the A1 / A11, most units won't go higher then ~ 440 to 450 VAC

 

[Guyfang]

This is a TQG, not a DED model. So no A1 or A11.

 

[peapvp]

Guy ( @Guyfang ) you posted the TM's for the 805B TQG in the TM section:

https://www.steelsoldiers.com/threads/all-the-tm-you-need-for-the-mep-804b.184812/

And you wrote:

" This should be all the TM's you need to work on the MEP-804B gen set. Basically, its the same books as the MEP-804A, with the addition of TM 9-2815-538-24&P, the new engine book. "

Now, these units have a AC Voltage Regulator A1, but the static exciter is separated out and not combined like in the A11 for the 004A 005A units

In either case, going up to maximum adjustable Voltage for any prolonged period of time will cause a problem for the Voltage Regulator, either the A1 or the A11.

Btw. thinking about it, maybe you can organize the links to each TM in the thread above. It may save someone from loosing their minds.
(Unless its only mixed up on my PC / Browser)

Peter

 

[Guyfang]

Now, these units have a AC Voltage Regulator A1, but the static exciter is separated out and not combined like in the A11 for the 004A 005A units.

Thats all I was really saying when I posted. They are not combined.

Links are not really a good thing. They can go dead. And the Generator TM forum is/will be undergoing change.

 

[peapvp]

Thanks Guy ( @Guyfang ) for your clarification! You know I would never question your infinite knowledge!

On another note for the interested Reader:

The Operators TM 9-6115-643-10 is for both models 804 Alpha & Bravo




The confusion usually starts here in the part of the TM: Starting Procedure under normal conditions:



the "required values" in # 7 should read "rated values"

This applies to any MEP Generator

Most 15Kw and higher Gensets have Load Sharing and Paralleling Modules installed. Those Modules may not be able to withstand operations at higher Voltages as well.