ST5 with AVR connection question

[buickanddeere]

 A 120V voltage regulator should work ok on a 240 generator when connected between neutral and either one of the lines. 120V motor starting would be "improved" if the regulator was on the same 120V line. The loads on the other line maybe briefly exposed to higher than rated voltages during the motor start.
 
 I solved the get full capacity dilemma on my 6kva generator with a surplus 10kva 120/240V to 600V transformer. Worth their weight in scrap copper after office renovations/tear downs at industrial sites.
     I left the 600V side open. The 120/240 Generator only supplies 240 to the transformer. Any unbalanced 120V is not seen by the generator, the transformer takes care of the imbalance. No more tripping the 6kva generator with 4kva loads.   

[vtmetro]

Anybody tried a very light counter spring yet?

Seems like that would be easier to work out than finding eactly the right new replacement spring.

Maybe just hook the counter spring in place and hold it by hand and pull on it while the engine was running to find the attachment point that is just short of hunting at the desired frequency.

[vtmetro]

A 120V voltage regulator should work ok on a 240 generator when connected between neutral and either one of the lines. 120V motor starting would be "improved" if the regulator was on the same 120V line. The loads on the other line maybe briefly exposed to higher than rated voltages during the motor start.

Exactly what I tried, only it was a 1500 watt heater not a motor. Serious scary hum from the generator that definitely did not seem healthy. I shut it down in seconds. Same load across paralleled 120V outputs with AVR is quiet.Same for 3kW.

I'm guessing that unbalanced unused circuit spiked bad,and wondering about generator insulation on that side.

Not going back to an AVR on one leg.

[Tijean]

You were hearing the ST growl from uneven loading of the 120 legs. some are worse than others; perhaps due to a difference in natural resonant frequency.. Do a search on  "growl" or "groan" for lots of reading. I dont like the sound of it but it does not appear harmful. There is apparently a cure though!

[vtmetro]

Thanks again Tijean, you've been very helpful. Did some reading and found this, which is exactly what I want to do for the house transfer switch.

Nothing really new here.  If you wire ST for 240/120, you will get hum proportional to amount of electrical load unbalance.  If you wire ST for 120, ST is always balanced and hum will be minimal (but your mileage may vary depending on state of your ST bearings).  You can also wire ST for 120 and easily feed 120 to both sides of your house panel (via a transfer switch) provided all the panel circuits you want to feed from ST are 120 (not 240 double-pole CBs).  Wiring ST for 120 also had added benefit of being able to supply full 3KW to one panel circuit should you need to do so.  You can only get 1.5KW if you wire for 240.

I don't need to power anything 240v in a power outage, but currently have a two leg transfer panel setup now. So I'm going to look into changing that to work with the parallel 120 out of the ST-5. I've only got about 3kW supply out of a 6-1 anyway, so why split it up if I'm powering only a few 120 V house circuits in an emergency?

For shop use I bet I can work out a switching arrangement near the ST to get 240v at that end when occasionally needed, while running parallel 120 at other times. Shop power would be off when supplying the house in an outage.

[buickanddeere]

  It grows to be both a nuisance and an opportunity to blow some electrical load to bits when swapping voltages.
  Either a larger generator head (preferred) such as a 7.5KW which can carry full engine power on one half of the generator. Or kind a 6+ KW 120/240 transformer and monkey up the same system I did.

[vtmetro]

  It grows to be both a nuisance and an opportunity to blow some electrical load to bits when swapping voltages.

As with anything it depends on how you design it.

[Tijean]

Thanks again Tijean, you've been very helpful. Did some reading and found this, which is exactly what I want to do for the house transfer switch.

Nothing really new here.  If you wire ST for 240/120, you will get hum proportional to amount of electrical load unbalance.  If you wire ST for 120, ST is always balanced and hum will be minimal (but your mileage may vary depending on state of your ST bearings).  You can also wire ST for 120 and easily feed 120 to both sides of your house panel (via a transfer switch) provided all the panel circuits you want to feed from ST are 120 (not 240 double-pole CBs).  Wiring ST for 120 also had added benefit of being able to supply full 3KW to one panel circuit should you need to do so.  You can only get 1.5KW if you wire for 240.

I don't need to power anything 240v in a power outage, but currently have a two leg transfer panel setup now. So I'm going to look into changing that to work with the parallel 120 out of the ST-5. I've only got about 3kW supply out of a 6-1 anyway, so why split it up if I'm powering only a few 120 V house circuits in an emergency?

For shop use I bet I can work out a switching arrangement near the ST to get 240v at that end when occasionally needed, while running parallel 120 at other times. Shop power would be off when supplying the house in an outage.

Before you make that hookup; I think there may be a potential problem in supplying both sides of your panel from a single 120 source. Maybe not but it should be checked before you throw the switch. The person quoted mentions dual pole circuits. Another name may be Duplex. I have a few of them installed and would have to do some thinking about consequences. Maybe a real electrician will chime in here.

Something sounds weird with that intermitten self loading and voltage drop when the legs are parallel.

[vtmetro]

Thanks Tijean, I won't be doing any hookups at all until I'm satisfied with the genset performance.

As far as paralleled 120V for the emergency house circuits go, that would go to the transfer switch for emergency use only, which is the type that actually has 6 individual transfer switches, one for each house circuit. The transfer box is separated into two legs, but doesn't need to be. The circuits are all isolated from the main box when their transfer switches are thrown.

[Tijean]

VTmetro, that sounds like OK. with proper isolation of the circuits via the transfer switch. What do you do about bonding the neutral of the generator?

[vtmetro]

Just to repeat, I'm not doing this until I get the genhead problem straightened out first.

Briefly, (not mentioning CB's here and ground rod) Hot gen 120v goes to both red and black wires to the transfer switch. Neutral Gen output goes to white wire to transfer switch. Green gen ground goes to green @transfer switch.

*********

Also, to explain one possible method of getting occasional 240 and otherwise parallel 120V (exclusive usage):

Mount on the wall two small panels -- one for 120, one for 240. Each has a recessed male 4 prong socket,

The gen head has a cable that brings out U1,U2, U5, U6 into a mating female connector. Connections between the gen output lines for 240V  or 120 parallel are made in the respective panel. Lead-outs from the panels go to appropriate 240 or 120 outlets.

I'd probably hard wire the AVR sense leads into the 120 panel, and the AVR would only be functional on 120V. My genset pulley ratio tends to run voltage a little high at 60 Hz so I'd set up for 61 hz and check 240 against the load -- likely to be a motor or welder to make sure the drop and freq were acceptable.

Alternatively, you could switch the AVR between the two with more design compexity, but you'd need a method of mechanical lockout to make sure the connectors would only mate when the switch was in the proper position. Maybe a switch mechanically determining which connector had a cover over it -- similar in concept to the lockout slider plate on a homemade breaker switching transfer box.

[vtmetro]

Okay so now I'm back to thinking abut my selectable 120V parallel and 240 V connections.

To reiterate, two panels. Each panel would have a recessed male 4 prong connector to connect to the generator.

The generator would have a cable output with a mating 4 prong female connector. It would bring out U1 U2 U5 and U6.

Each panel would shunt the leads together properly internally to configure for its output voltage, 120 or 240.

Originally I thought to put the AVR in the 120 panel, and leave the 240 panel unregulated.

But:

In researching genhead prices last night (when I thought mine might be bad) I found Tom Osborne's Ebay store, and noticed I could buy a replacement AVR for $49.

So perhaps it would be possible to have two AVR's and put the original AVR in the 120V parallel panel, and the second one in the 240V panel.

Not sure if it would be possible to do because both outputs must be connected to the stator -- they might interfere with each other. (The input lines of one AVR would always be disconnected, however.)

This type of AVR has output leads that are typically spliced (according to Tom's docs) in series into the Z1 (or Z2) stator lead.

http://www.centralgagenerator.com/documents/avrpics/AVR110-Silver,-Blue-end.jpg

With two AVRs I'm not sure if you would need to connect their outputs in series with each other, or in parallel. My guess is series and that the AVR simply acts as a variable resistor.

I'm also not sure if the input lines of the unused AVR need to be shorted together or whether an open is an acceptable input state. I suppose I could test that on a single AVR with its output connected normally.

Note, the AVR output leads would be hardwired from the panels to the generator. They are not part of the cord with the connector.

I'm not planning a dual AVR experiment (yet), and will probably just set up panels with a single AVR on the 120 parallel as explained earlier.

But if I got more information about the AVRs operation and it proved do-able, dual AVRs is how I'd ultimately like to set it up.

[Tijean]

Dual AVR's may be ok as long as they dont duel! You would have to think that setup through very well. It may not be necessary or any advantage to having two since only one leg is monitored and the field is only one circuit in either mode of connection. Maybe the AVR could be left fixed to the gen.

You might want to have a sliding cover on the panel that always covers the unused recessed male connectors when they would be hot. It sounds interesting and very much in line with my own situation.

[vtmetro]

Dual AVR's may be ok as long as they dont duel! You would have to think that setup through very well. It may not be necessary or any advantage to having two since only one leg is monitored and the field is only one circuit in either mode of connection. Maybe the AVR could be left fixed to the gen.

On my genhead the AVR goes across U1 and U6 for 240V and U5 and U6 for 120V. A single AVR could be used if U1 and U5 were switched. As I mentioned earlier, a mechanical lock-out could be used to do this when reconnecting. In fact no harm would occur by failing to switch the AVR, other than the fact that it wouldn't be regulating.

For a lockout, something that blocks the receptacle until you move the switch would work.

A final possibility would be a 5 (or 6 wire) connector, but I imagine a suitable set of those would be nearly impossible to find, or cost more than the gen head. Could be wrong there, as someone may point out....

Curiosity has got me considering the two AVR method, however.

[bschwartz]

Errr.... I must be missing something.  Why dual AVRs?  In either configuration 120/240, you can still measure the voltage across one 120 leg for the AVR.
Simply connect it between U1 and U5 or U2 and U6.  No need to change anything else.