HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
<<  <  Page 3/5  >  >>
Rob Spiegel
User Rank
Blogger
Re: MECHANICAL GOVERNORS...
Rob Spiegel   1/6/2012 11:01:44 AM
NO RATINGS
Interesting, VA Mech Eng. I would imagine you have a lot riding on your generators, since life-sustaining medical equipment would depend on the generators during a power failure. Have you received any concerns about the quality of the power from the generator? I would imagine both IT and the medical equipment team would need some reassurance. 

VA Mech Eng
User Rank
Iron
Re: MECHANICAL GOVERNORS...
VA Mech Eng   1/5/2012 7:34:25 PM
NO RATINGS
Rob,

 

Go to the 2nd page of comments and read my remarks. In short, there is nothign wrong with mechanical governors and self exciting windings.  I actually prefer them, and is what I have on my home back up generator.  You do need to make sure that the two are designed to work with each other first though.  I work at a VA hospital and almost none of our generators (and we have something like 15 of them) have electronic controls to control their speed. Most of our generators are between 10 and 40 years old and work just fine to back up even our entire IT department!

robatnorcross
User Rank
Gold
MECHANICAL GOVERNORS...
robatnorcross   1/5/2012 5:33:59 PM
NO RATINGS
I figured "engineers" would know better than this. "Homeowner" type generators use the same type mechanical governor that's on your LAWNMOWER. These things barely run power tools within their limits. Most are self excited with diodes used in the armature and only produce 120V at 60 Hz if your lucky on a good day. Larger (spelled more expensive) units have electronic controls that control the throttle to regulate the frequency. Another circuit is needed to regulate the voltage by changing the excitation.

Ken E.
User Rank
Gold
Re: Similar woes experienced.
Ken E.   1/5/2012 3:53:41 PM
NO RATINGS
Ann, you are right to be worried, yet generators do computer back-up all the time, all the way up to huge units on big server farms.  The simplest way to cya, is to oversize considerably, say 5x expected load.  This essentially adds enough rotating inertia to ride through power consumption surges, and it also tends to get you into a bigger generator with more sophisticated controls.  I spoke to several generator installation 'professionals' who had experienced pains identical to mine, and that's their general work-around.

In your situation, i.e. a remote area, where you may be using the generator to power other equipment as well as electronics, the 5x number refers only to the electronics, particularly the UPS's, which may be switching groups of equipment. I did another back-up generator that supports a call center plus I.T. equipment, and the I.T. equipment was a small enough percentage of the total, that a generator only 2x the connected load worked without a hitch.

If you really want clean power, spring for a Constant Voltage Transformer between the generator and electronics.  They are pricey, but very effective, reliable passive devices, offering very clean power output, no matter the trashy input you apply.

Good Luck, Ken

Ann R. Thryft
User Rank
Blogger
Re: Similar woes experienced.
Ann R. Thryft   1/5/2012 12:50:15 PM
NO RATINGS

Wow, sure glad I read this MBM and especially all the comments. We are looking into various power supply, marine battery and inverter combinations to deal with the occasional power outage here in the redwood forest. Since our main purpose is to keep computers going, and for other reasons, generators aren't always the best option. Their power is usually too dirty for computers, mostly, as I understand it, because of that lack of voltage regulation. But this instance really takes the cake. Sounds like more lousy quality control, or rather, a lack of QC. 


Rob Spiegel
User Rank
Blogger
Re: Similar woes experienced.
Rob Spiegel   1/5/2012 12:45:21 PM
NO RATINGS
Hi Ken,

This is a good story. I'd like to use it as a Sherlock Ohms posting. Is there an end to this story? Sounds like it's close.

Could you send me permission to use the story? Also, I would need a short bio (three or four sentences).

Send to: rob.spiegel@ubm.com

Ken E.
User Rank
Gold
Similar woes experienced.
Ken E.   1/5/2012 12:36:48 PM
NO RATINGS
Yes, one has to know what they are doing when hooking these things up, but I expect I'd have done it the same way for my home.

As plant engineer, I was asked to install a fairly small (10kva) 120/240v/1Ø back-up generator and transfer switch for a small computer equipment room, which contained servers, network switches, and telecom equipment, most of which is UPS backed for the short term.  Even 'qualified' electricians can make mistakes, in this case misidentifying the generator ground lug as the neutral lug.  Without a neutral, when the two 120v loads are not balanced (and they never are) the voltage will go high on the least loaded side, low on the other.  We lost some minor equipment, similar to the case here.

But that was not the end of the problems.  Although the generator was 3x oversized for the connected load, we experienced problems with stability.  When a transfer to generator was made, all the UPS's saw the voltage and frequency return to 'normal', and they all switched on.  This caused the generator to suddenly load, slow down, voltage and frequency went outside acceptable range, all the UPS's turned off, then the whole chain of events repeated.  What I need is the 80 pound flywheel that another reader mentioned, but that's not an option at this point.  There were occasions when we did actually stabalize and everything ran, but the reliablility isn't up to snuff.  And every switch of any UPS change of state triggers an automated email!

A search of the net bore very little fruit, except to suggest oversizing the generator even more.

My next option is to add some timers and relay's to sequentially load the various equipment in three steps, reducing the load spikes to somewhere within the working envelope of the rotating inertia and regulation capacity available. 

My reputation has taken a quite a hit with our I.T. department, they are suggesting they should have had it done 'by a professional', which up till now I had considered myself.  Yeesh!

Ken

 

dmpflumm
User Rank
Iron
Inexpensive Solution
dmpflumm   1/5/2012 10:59:51 AM
NO RATINGS
A low cost panel meter that displayed the AC voltage for both the 110 & 220 VAC would have made the design more safe... not foolproof but more safe.

At the very least a warning lamp for over/under voltage conditions could be implemented relatively cheaply... but still not foolproof as the user would have to read the manual and be aware of it's indication.

Possibly the best solution would be to include a under/over voltage contactor, but this would add expenses to an already very competative market.

Bullsofchgo
User Rank
Iron
Re: B & S quality, a thing of the past...
Bullsofchgo   1/5/2012 10:18:32 AM
NO RATINGS
I don't think the price of a particular model by a manufacturer should govern the quality and safety of a product. There should be some baseline for that regardless of the model. Generally there should only be enhancements and additional bells and whistles. Maybe the life of the product of say 5 years vs 10 years or something. Any company that does differently is only hurting their reputation and will end up on the trash heap of deceased companies.

Walt
User Rank
Gold
Re: B & S quality, a thing of the past...
Walt   1/5/2012 9:55:14 AM
NO RATINGS
I've also had bad experiences with B&S engines that were not of the rugged old vintage.  After having the B&S V-twin engines of two Simplicity tractor/mowers self destruct (though well maintained), I've moved to Kohler...

I do still have an old push mower with a B&S that still runs great, but will be hesitant to buy a new one.

<<  <  Page 3/5  >  >>


Partner Zone
Latest Analysis
Hacking has a long history in the movies, beginning with Tron and War Games and continuing through The Girl with the Dragon Tattoo.
In a move that strengthens its 3D design business, Stratasys continued a 15-month buying spree this week by announcing its plan to acquire GrabCAD, a provider of a cloud-based collaboration environment for engineers.
Feature-advantage-benefit could help engineers in how we approach design problems, how we sell our ideas to management, and how we market ourselves when it comes to jobs.
Many diverse markets take advantage of semiconductor IP; so many that no one can recite the entire list without leaving off several. So why do we track all the vertical markets? They all have a unique set of requirements and value attributes differently. One major vertical market segment is automotive.
Adam Berger hacked a computer keyboard into a mini key-tar to play with his band.
More:Blogs|News
Design News Webinar Series
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
7/17/2014 11:00 a.m. California / 2:00 p.m. New York
6/25/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Sep 22 - 26, MCU Software Development A Step-by-Step Guide (Using a Real Eval Board)
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: September 30 - October 2
Sponsored by Altera
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service