Author Topic: ST 7.5 Missing Terminals and other questions  (Read 4892 times)

DirtMerchant

  • Jr. Member
  • **
  • Posts: 91
    • View Profile
ST 7.5 Missing Terminals and other questions
« on: June 30, 2013, 09:15:54 AM »


Finally pulled some power from my 6/1 -ST 7.5  yesterday but am a bit confused, the instructions that came with it were useless.  From images I have seen here it would appear I am missing a couple terminals on my gen head board?  I also am not sure what the switch on the front of the doghouse is supposed to do? The generator produces power as soon as  it spins up regardless of the switch position, the switch seems to just turn on the little red light on the doghouse but that's all ?  Maybe due to the way I am pulling power? In the photo you can see the romex tied to what I believed is 1 110v leg. I produces power and I pulled 1000 watts from it with no issue other than a weird intermittent rhythmic hum. The silly meter on the front shows 200v regardless of RPM or load....thinking it doesn't work properly?


BruceM

  • Hero Member
  • *****
  • Posts: 3054
    • View Profile
Re: ST 7.5 Missing Terminals and other questions
« Reply #1 on: June 30, 2013, 12:54:51 PM »
The doghouse has so much vibration that it should be removed. The light is a harmonic winding active indicator, which is silly and worthless. 

If your set up is for 120V-N-120V with 240V between the two hots, then yes, you can expect growling with 1000 watts of load applied to only one of the 120V legs.




DirtMerchant

  • Jr. Member
  • **
  • Posts: 91
    • View Profile
Re: ST 7.5 Missing Terminals and other questions
« Reply #2 on: June 30, 2013, 02:00:05 PM »

 The growling seems intermittent though and doesn't seem to coincide with flickering or changing loads...is that normal when loading only one leg?


Thob

  • Sr. Member
  • ****
  • Posts: 255
    • View Profile
Re: ST 7.5 Missing Terminals and other questions
« Reply #3 on: June 30, 2013, 02:34:11 PM »
My ST 7.5 also came without the 2 extra terminals.  Those terminals were connected to additional turns on the main windings to provide 220V at 50 HZ - at the 1500 RPM needed for 50HZ, the generator doesn't produce enough voltage, so extra turns were provided.  In the US market, no one needs 50HZ, so they saved money by not including them.

Between the two center terminals there should be 2 links stacked together (it may look like one link at first).  Remove the two links and put one to each of the two outer terminals, and you'll have rewired the head for parallel operation, or 120V only.  That should eliminate the hum from the unbalanced load created by only using one side of the windings, but leaves you without 240V.  There are ways of digging into the internals and re-wiring it for 240V that won't hum, but it's not a quick easy mod.

The idiot light and switch don't do much - mine was wired to the 120V output (I think), not the harmonic winding.

You can either replace the doghouse or wait until it falls apart and then replace it; when you do, it's not too hard to create a receptacle on the generator side with all four wires and two different plugs to match with it - one that puts the windings in series for 240V and one that puts them in parallel for 120V only.  Don't change it while the generator is running!

If you leave it wired for 240V, normally the center terminals (where the links currently are) are used as the neutral, or white wire.  Electricity doesn't care what color the wire is, but following the standard will be helpful in the long run.
Witte 98RC Gas burner - Kubota D600 w/ST7.5KW head.
I'm not afraid to take anything apart.
I am sometimes afraid I'm not going to get it back together.

DirtMerchant

  • Jr. Member
  • **
  • Posts: 91
    • View Profile
Re: ST 7.5 Missing Terminals and other questions
« Reply #4 on: June 30, 2013, 07:51:54 PM »
My ST 7.5 also came without the 2 extra terminals.  Those terminals were connected to additional turns on the main windings to provide 220V at 50 HZ - at the 1500 RPM needed for 50HZ, the generator doesn't produce enough voltage, so extra turns were provided.  In the US market, no one needs 50HZ, so they saved money by not including them.

Between the two center terminals there should be 2 links stacked together (it may look like one link at first).  Remove the two links and put one to each of the two outer terminals, and you'll have rewired the head for parallel operation, or 120V only.  That should eliminate the hum from the unbalanced load created by only using one side of the windings, but leaves you without 240V.  There are ways of digging into the internals and re-wiring it for 240V that won't hum, but it's not a quick easy mod.

The idiot light and switch don't do much - mine was wired to the 120V output (I think), not the harmonic winding.

You can either replace the doghouse or wait until it falls apart and then replace it; when you do, it's not too hard to create a receptacle on the generator side with all four wires and two different plugs to match with it - one that puts the windings in series for 240V and one that puts them in parallel for 120V only.  Don't change it while the generator is running!

If you leave it wired for 240V, normally the center terminals (where the links currently are) are used as the neutral, or white wire.  Electricity doesn't care what color the wire is, but following the standard will be helpful in the long run.


Thanks that is helpful information (not the changing the doghouse when its running part, if I was that stupid I would deserve being removed from the gene pool :) )

Ya I know the white normally goes to neutral, was in a hurry and just had it wired to a single outlet to put a load on it...then used a suicide cable to back feed the shop to put a real load on it :)

« Last Edit: June 30, 2013, 07:53:48 PM by DirtMMerchant »

BruceM

  • Hero Member
  • *****
  • Posts: 3054
    • View Profile
Re: ST 7.5 Missing Terminals and other questions
« Reply #5 on: June 30, 2013, 08:41:43 PM »
My St-3 had bad bearings right off of the pallet, and would "groan" more as the load increased. Growling and groaning could be your bearings, as well as the usual unbalanced load issue.

Bshwartz (sp?) on the microcogen.info site came up with a brilliant wiring change to eliminate the growling, but you do have to disassemble and remove the rotor and it is not for the faint hearted.