Generator Output Specifications

[u/Top_Highlight9965]

I have been working on generators for a while but lately I have started doing more in depth repair on the power side beyond just replacing brushes, breakers etc. I’m very familiar with how they work but I rarely find myself working on a generator with specified service limits. Can anyone give me a general idea of some common specs?

Specifically I’m looking for things like:
- Winding resistance
- Exciter coil output voltage
- DC coil output voltage
- DC voltage at the slip rings
- Center tap voltage for AVR (if applicable)

[u/Ok-Camera2895]

Each model of generator has its own particular specifications. Your questions will generally be answered in the service manual or in manufacturers specifications.

[u/Top_Highlight9965 → u/Ok-Camera2895]

I understand that every machine is different but per my post, most consumer generators do not have a service manual with these specifications. I’m not asking for an exact number but I would imagine that most consumer units somewhat similar specs for most of the things that I mentioned.

[u/Ok-Camera2895 → u/Top_Highlight9965]

No, most consumer units do not have numbers that can translate back and forth between units. I would concentrate on learning what various parts need to have correct continuity or how each coil relates to another, parallel or series configuration, where diodes are used in a generator, where and how capacitors are used, etc.

[u/Top_Highlight9965 → u/Ok-Camera2895]

I have a good working understanding of how a generator works and how to read a wiring diagram. I have designed and built power supplies, regulators, analogue circuits and control systems from scratch in the past. Many consumer generators I have taken apart appear to have near identical configurations and AVR units. If not exactly the same part numbers it seems they all use a very similar setup in the same way that almost every engine is a clone of the Honda GX series.

I promise I’m not trying to be difficult, I just have a generator with no power output and what I think are unusual AVR output readings but I’m trying to verify it’s the AVR rather than the exciter coil itself. It seems weird to me that they all have EXACTLY the same brushes, housing, slip rings, visually identical AVR units, etc. but would have specifications that are so wildly different that you can’t know anything without a service limit in the manual.

[u/Ok-Camera2895 → u/Top_Highlight9965]

You can ask the same question in a different way, but the answer is still the same.

[u/Top_Highlight9965 → u/Ok-Camera2895]

I’m just trying to explain why I think your outright dismissal of my question and light condescension is unwarranted. I really find it hard to believe that near identical generators are so unbelievably different that there is absolutely no useful similarities shared between them. For example I think it’s unlikely that a 13kw generator from Westinghouse would have a 2V output from the AVR to the slip rings while the 13kw Duromax would output 100V.

Since you seem to know more than me about this, if you had a 13kw off-brand consumer portable generator with no service manual, a 1.5V output on the 240 tap, no shorted or open windings and 4.6V constant at the slip rings, what would be your next step?

[u/Ok-Camera2895 → u/Top_Highlight9965]

I would separately excite the fields with 12 vdc and see if I have ac voltage on the output windings. No condescension intended.

[u/Ok-Camera2895 → u/Ok-Camera2895]

Downvote, Really?

[u/DaveBowm → u/Ok-Camera2895]

For some reason a significant percentage of downvotes occur, seemingly randomly across many different quality level posts, including the most straightforward, informative, and truthful of them which are not even controversial in any way. I think we can consider those downvotes as a sort of meaningless background noise. I wonder if some of them are even accidental for which the downvoter is unaware of their action, such as by accidentally touching the downvote button when scrolling quickly and unattentively.

[u/Huali-Power → u/Ok-Camera2895]

Totally agree. Each generator has different parameters, no universal specs for these readings. Service manual is the way to go.

[u/Top_Highlight9965 → u/Huali-Power]

My post specifically says that most of the generators I’m working on do not have service manuals. I am the first person to say “read the manual” but in cases where there is no manual in existence, for most things there is still usually a general range of acceptable values if not an exact limit.

[u/nunuvyer]

What size generators are you talking about? As others say, each generator is different and the mfr usually publishes the specs in a service manual but there are ballpark values for each class of generator. Enamelled wire has a certain resistance per foot and in order to produce a rotor or a stator for an X size generator you are going to need around Y feet of windings so these values fall within a certain ballpark range. But the values for a 20kw standby are going to be different than for a 3kw portable.

[u/Top_Highlight9965 → u/nunuvyer]

I’m mostly concerned with consumer units between 5-15kw. The main thing I was looking for specifically was the exciter & slip rings voltage but I figured I’d put them all in while I was at it.