Dyno Operation Control Problem

[charlie10]

Friend has a new Dyno unit (device that measures HP of auto). It has a 20 amp 220 volt main feed and a seperate 120 volt control unit feed. Unit works properly with a generator but not from the utility feed. This is at his house in the country so has a utility pole transformer with a 200 amp feed. The dyno is in another building a with a 100 amp main panel (4 wire feed from service enterance panel). Initial operation had diodes blowing on the control boards. Current problem is "warbeling" at certain speeds. At just below 50%, unit is pulling 7.5 amps, but between 50 - 65% is varies between 7 - 12 amps and is unstable. Once it gets above 65%, current levels back out to 10 amps. Turning on and off other breakers in the panels does effect at what point this "warbeling" takes place. Utility company has looked at the problem with no solution found. Equipment manufacture has no similar problems so states "unit works fine in 1000 other installations". Several people have suggested that he install a isolation transformer. Been working on this for over a month and justs wants to get the unit running correctly. Any suggestions on things to try or test?

 

[DougMSOE]

Who is the equipment manufacture?

 

[charlie10]

Superflow SF 840, Have had factory engineer out to try to resolve problems. Keep blowing rectifier units at low current flow. Presently have one controller that does seem to work but not at a steady state.

 

[charlie10]

Follow this post on another site for more details

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=007460#000006

Any suggestions??

 

[jbartos]

Suggestion to charlie10 (Electrical) Feb 16, 2004 marked ///\\Any suggestions on things to try or test?
///Even though the current around 12A may seem to look sufficiently low, the branch circuit, #14AWG or its IEC equivalent, 16Amps or 10Amps may experience noticeable voltage drop that affects the dyno performance. Also, the voltage waveform should be checked for its pure sinusoidal quality.\\\

 

[charlie10]

The unit is feed from a 40 amp 2 pole breaker (240 volt single phase) with #8 wire. Smallest wire in the system is #12.
Did have a Oscope on the feed line. Waveform kind of looked like a chair with the back to the left. Not very sinusoidal. Only found this waveform with the Dyno running.

 

[Rick360]

Sounds like it might be a bad neutral. Did you measure the voltage from neutral to both sides of the 240 when it is malfunctioning? If the 120V legs fluctuate in volatge when the individual 110V phases load change then that is whats going on.
The bad connection could be from the dyno to the box or from the box to the pole.

 

[charlie10]

Watching Power Co test neutral with their 20 amp "unbalancer" I saw the loaded leg drop about 4 volts to approx 116 while the unloaded leg rose 4 to approx 124 volts. Since this is still within spec range of 120V +/- 5% they are satisfied that it works.

Is it normal for the unloaded leg to raise the voltage?

Don't know what the overall load on the system was during the testing. Other testing showed the max draw over 2 days was 60 amps per line so not working the 200 amp service very hard.

 

[Rick360]

Was the power co. test done at the main breaker box? I assume it was.

If the full drop in voltage on one leg adds to the opposite leg, then the neutral feed is creating the full voltage drop, so it has significantly more resistance than the other wires (probably poor connection at the transformer).

With only a 20amp load on 200amp serv I can't imagine seeing even a noticeable drop in voltage on the loaded side (4 volts seems like a lot). Imagine how unbalanced the voltage would be if you had a large load on one side.

It doesn't have to be much resistance to cause a problem, just a few tenths of an ohm.

 

[jbartos]

Suggestion: It looks like there is some kind of transient phenomenon within the waveform half-wave causing harmonic distortion. It can be caused by a faulty switching device(s).