% Load on convenience outlets

[Boatcarpenter]

If you plug into the convenience outlets, does the %load meter give you the % load for those outlets or the whole set?
BC

 

[gimpyrobb]

The "CO" is only like 15amp. The % load is for the lugs.

 

[Boatcarpenter]

Thanks Gimp. I forgot to mention the genset is a MEP002a.
BC

 

[Crawdaddy]

Doesn't matter if it's a MEP-002 or -003. The convenience outlet is for very low-powered use.

 

[Boatcarpenter]

OK guys, here is the scoop.
Had some time to run a test today.
Wired a duplex outlet to my L3 and Lo.
Ran my nail gun compressor which is rated at 14 amps from the convenience outlet and the % load read about 25%, which is about correct for a 52 amp output unit.
Ran it on the duplex wired to the lugs and % load was exactly the same.
Compressor on cold start % load jumped to a little over 40%.
Warm startup a little under 30% load.

BC

 

[Keith_J]

Control transformer 1 (CT1) is what the % rated current meter is measuring. CT1 measures all windings, depending on position of S8.

NEVER run any load over 500 Watts, even though the circuit breaker is 15 amperes which will support a 1500 Watt load. Why? Because the outlets are driven by only one of the six windings. So even though the generator can put out 52 amperes at 120 volts, the outlet can only deliver 1/6th of that or 8-2/3 Amperes (8.66 amps).

When one winding is loaded, the control voltage transformer along with the voltage regulator boost field voltage to compensate. This causes the other unloaded windings to generate higher voltage which can break down insulation. Running 15 A off the outlets also heats the one loaded coil and thermal expansion conspires with the voltage stress to break down insulation.

When the windings are uniformly loaded, the heating is uniform and very little thermal stress happens.

 

[Isaac-1]

Keith, you keep saying this, and while I have not looked at the schematics for the MEP-002/003 I can't see how it can be true, since the tie points for all of the connection options for the output voltages would parallel at least 2 windings, meaning the minimum in 3 phase mode would be 1/3 not 1/6 of the output, which would be at least 1600 watts on a MEP-002. Electricity just does not behave the way you seem to be implying if does since it would flow through both the parallel windings even if the physical connection were to only one tie point.

Ike

 

[ETN550]

I'm not sure about the 002 / 003 but they do take the outlets off of one of six windings. This is a direct take off upstream of the reconnection switch. On the 016b which has three windings the outlets are taken off of winding #1, T1-T4. The interesting thing is that in the 120VAC single phase mode the tap points for the outlet are the same for L1 - L2 which is the whole rated load output. Therefore, it can be run up to the fuse limit. Note that in addition to the 120 outlets the same source is used to supply the frequency transducer and a transformer for the field supply.

I think there are some modes on the 002 / 003 where the #6 outlet winding is paralleled with another winding. In that case the outlet load can be safely doubled. In modes where the outlet winding is not in parallel with any other winding then it can handle only a small amount of power.

Lesson: Know how it is wired and do not exceed the winding capacity, but take advantage of parallel windings.

 

[storeman]

Soooooo. How does one determine parallel windings if they only occur on some models? I have 2 002a's and a "parts" 003a. How would I recognize parallel or not?
Jerry

 

[ETN550]

Soooooo. How does one determine parallel windings if they only occur on some models? I have 2 002a's and a "parts" 003a. How would I recognize parallel or not?
Jerry

Hi Jerry,

Got to look in your manuals for the connection diagrams. Not the big complicated wiring diagrams. Usually where the manual talks about which output lugs to use for the selected voltage and phase. They depict the windings like zig zag lines and show them arranged in a triangle fashion or laid out in a line. I thought someone posted some diagrams for your gen on here not too long ago. Any 002 owners got one handy??

 

[storeman]

etn550
Thanks. I'll dig deeper.
Jerry

 

[Crawdaddy]

I have the output lug and coil diagram in my post here:

http://www.steelsoldiers.com/907957-post1.html

 

[ETN550]

Hi,

Thanks for posting that up. Others chime in if I mis speak. It looks to me that the #6 winding would be represented by the coil with the 9 - 12 terminals.

If that is true then for the 120vac single phase mode the main lug terminals are coincident with the 9-12 coil. Therefore, the entire load could be taken at the convenience outlet. Of course the fuse on the outlet is going to limit that.

For the 120 / 240vac mode the 9 - 12 coil is coincident with lugs for one side of the 120vac. Therefore, half the full output could be taken through the convenience outlet. Again, the fuse on the outlet will limit that. Note that this 240 / 120 mode is one of the modes where balancing the 120vac loads between the two sides comes into play.

The key here is to be comfortable that the outlet is indeed connected to one of the coils on the bottom of the triangle, coils whose terminals are the same as the output lugs. If for some reason the coil feeding the outlet happens to be one of the other coils on the side of the triangle and is not directly common with the output lugs then the outlet capacity is greatly reduced.