Poor AC Generator power quality

[Poozer]

It's not a 6 KVA when its running split phase, and supplying from one leg into the load on only half the phase. Not to mention the VFD is only good for about 2/3rds it 3 phase rating when running from single phase.

Now factor in that it's running on 1 leg out of balance on split phase...that's why we have peak clipping, and so much impressed harmonics. Not to mention the fact that the half phase of the split is near maxed out.

Lloyd

Is it really running split phase? It's wired up as per Figure 26 in this generator wiring diagram. Plus, I have measured 45 amps at 120V = 5.4kVA (not 6 kVA, but more than 50% of the output).

[Adamante]

BTW, have you had a chance to check the brushes? Do they look OK? According to the manual, they should be changed every 3,000 hours.

[transmitterdan]

Originally Posted by Poozer

Is it really running split phase? It's wired up as per Figure 26 in this generator wiring diagram. Plus, I have measured 45 amps at 120V = 5.4kVA (not 6 kVA, but more than 50% of the output).

In that configuration it is not split phase. It has two windings in parallel. If you have the ability to load test you could try testing each winding to see if one is weaker than the other. U1-V1 is a winding and U2-V2 is the other winding.

[Poozer]

I took my air compressor to the local Onan dealer today and tested it on the 5.0kW Onan unit. The Onan had no problem running the compressor at 120V 60Hz. I will be running the same test tomorrow on a 7.6 kW Westerbeke, and may need to make a choice between the two units.

• Things I like about the Onan are: Very tight frequency control. Integrated sound enclosure that will fit in my genset locker (which is pretty tight height-wise). 5 year warranty and extensive dealer network in the South Pacific.
• Things I don't like about the Onan: It's only 5kW, so it's a bit on the small side for our needs (the larger model Onan won't fit in our locker). It runs at 2900 RPM, with a 2 cylinder engine and seems quite loud. It's more expensive than the larger 1800 rpm 3-cyclinder Westerbeke. It's hard to fix myself if it breaks. It has a brushed alternator section.

A local diesel mechanic told me that Westerbeke is nowhere near the quality of Northern Lights or Onan and will fall apart over time. There are a lot of opinions floating around on the forums, but most people love their Westerbeke generators and all of them comment on how quiet they are. Some on this forum list Westerbeke as not being as reliable as Onan, but it's hard to separate fact from fiction.

At the end of the day, I want a genset that can run all the loads on my boat. Is quiet, has good southern hemisphere dealer representation, and is reliable.

I would appreciate any thoughts you folks have on one vs the other!

Thanks,
Doug

[transmitterdan]

First I would load test your NL generator on each 115V winding independently. If the Onan worked so too should the NL. Perhaps one winding is not working right. It could be something as simple as the excitation circuit isn't working right.

I think the local mechanic might be exaggerating a bit about Westerbeke. Their quality is good. They charge quite high prices for spare parts but then what supplier doesn't. The Westerbeke runs at 1800 RPM for 60Hz applications. That's a good thing.

If you want the peace of mind a new unit brings then my experience with Westerbeke has been good. NL is also good. Have no experience with Onan in boats but their commercial generators are well liked. If I had a choice I would choose the slower RPM generator.

[ebaugh]

I have a 1985 Westerbeke that was commissioned with the boat when new, along with a Kohler. No Onan experience. The Kohler was replaced with a new NL, in part since the previous owner accidentally doused the back end with salt water. I found that Westerbeke still fully supports parts for a 1985 unit, The Kohler guys just laughed. The Westerbeke looks almost new, and has run flawlessly for the 4 years we have owned the boat, but only has about 2300 hours on the clock.

I second the 1800 RPM recommendation.

The biggest strength of NL is it's a solid simple generator to work on, and in the Caribbean at least, there are quite a few dealers for support and parts. Westerbeke parts for the most part would have to be ordered in from the States.

I may have missed a post...have you given up on your NL?

[Poozer]

Originally Posted by ebaugh

I have a 1985 Westerbeke that was commissioned with the boat when new, along with a Kohler. No Onan experience. The Kohler was replaced with a new NL, in part since the previous owner accidentally doused the back end with salt water. I found that Westerbeke still fully supports parts for a 1985 unit, The Kohler guys just laughed. The Westerbeke looks almost new, and has run flawlessly for the 4 years we have owned the boat, but only has about 2300 hours on the clock.

I second the 1800 RPM recommendation.

The biggest strength of NL is it's a solid simple generator to work on, and in the Caribbean at least, there are quite a few dealers for support and parts. Westerbeke parts for the most part would have to be ordered in from the States.

I may have missed a post...have you given up on your NL?

That's good to hear about the Westerbeke. The problem isn't really parts availability. These days with Fedex, I expect I can get parts pretty much everywhere (even in Australia!) the issue is there are no technical people available that can troubleshoot the back-end of a Nothern Lights genset. Fixing anything on the motor is trivial, the Luggers are simple and everyone knows how to service and repair them, replacing an AVR or relay board is no problem. But figuring out why a 5kW Onan runs a VFD air compressor and a 6kW NL will not, that's non trivial and I can't find anyone to help me. It may be that NL generators, as reliable as they are, just aren't capable of handling more complex loads such as those presented by a VFD.

I'm going to have to replace the generator in order to break out of the loop I'm in:
1. NL says the generator is fine, the air compressor VFD is the issue. Talk to Brownies
2. Brownies says the VFD is fine, works on tons of generators, your generator is faulty - GOTO 1

[Adamante]

From what I have read, Onan has a good reputation and a rock-solid sinusoidal waveform, even when overloaded. If you still have access to the Onan, you might confirm that with your analyzing scope - it would be interesting to compare the readings with your misbehaving NL.

However, the 3,000 RPM vs. 1,800 RPM would give me a pause. On a boat, in close quarter, noise level is of paramount importance.

Not to beat a dead horse, but I’m a bit puzzled by the seeming reluctance to perform even basic tests on the NL, especially after dropping $2K+ on a fancy scope. If it were my unit, I’d at least check the brushes and slip rings. If the brushes have really not been changed in 6,000 hours, you might be down to bare metal.

The other thing I’d check is the resistance of all the windings (after disconnecting the AVR) for consistent readings. You can use a regular DVM for this.

And lastly, I’d make an effort to megger the windings. You can buy a Chinese megger for around $50 on ebay. Don’t know how well this kind of cheap unit works, but you could always confirm/calibrate it on a known good motor or transformer.

Should any of these tests indicate an anomaly inside the generator, I’d be tempted to pull it and turn it over to a motor rewind shop. There must be some in Brisbane. A rewind/rebuild might be more economically attractive than a replacement of the whole genset. The problem might even turn out to be something simple like a carbon dust buildup that could be pressure-washed out with solvent.

However, if you feel a need to buy a brand-new genset anyway, it’s your money. I just wish I were based in Australia so I could help you “dispose” of the NL.

[Lake-Effect]

Question - are you able to load up your NL genny up to rated power (6 kW) with resistive loads? Like six 1 kW baseboard heaters? And did NL get back to you with feedback on the waveforms and THD?

Originally Posted by Poozer

...the issue is there are no technical people available that can troubleshoot the back-end of a Nothern Lights genset. Fixing anything on the motor is trivial, the Luggers are simple and everyone knows how to service and repair them, replacing an AVR or relay board is no problem. But figuring out why a 5kW Onan runs a VFD air compressor and a 6kW NL will not, that's non trivial and I can't find anyone to help me. It may be that NL generators, as reliable as they are, just aren't capable of handling more complex loads such as those presented by a VFD.

I'm going to have to replace the generator in order to break out of the loop I'm in:
1. NL says the generator is fine, the air compressor VFD is the issue. Talk to Brownies
2. Brownies says the VFD is fine, works on tons of generators, your generator is faulty - GOTO 1

It comes down to:
1) the 6 kW NL will never run your compressor, for design reasons
-or-
2) there's something wrong with your NL generator

From your feedback I'm still thinking #2, especially if a new 5kW Onan can handle the compressor load. However if you say you are able to draw 6 kW from your NL, while not exceeding mfr specs for THD and waveform... then I would lean to #1.

If I were in your deck shoes, I would look for help from a company that sells/services industrial generators; they're more likely to have someone who understands generators more thoroughly. I googled 'generator Brisbane au' and had several hits including City Generator and AusGen.

Good luck.

[Poozer]

Originally Posted by Adamante

From what I have read, Onan has a good reputation and a rock-solid sinusoidal waveform, even when overloaded. If you still have access to the Onan, you might confirm that with your analyzing scope - it would be interesting to compare the readings with your misbehaving NL.

However, the 3,000 RPM vs. 1,800 RPM would give me a pause. On a boat, in close quarter, noise level is of paramount importance.

Not to beat a dead horse, but I’m a bit puzzled by the seeming reluctance to perform even basic tests on the NL, especially after dropping $2K+ on a fancy scope. If it were my unit, I’d at least check the brushes and slip rings. If the brushes have really not been changed in 6,000 hours, you might be down to bare metal.

The other thing I’d check is the resistance of all the windings (after disconnecting the AVR) for consistent readings. You can use a regular DVM for this.

And lastly, I’d make an effort to megger the windings. You can buy a Chinese megger for around $50 on ebay. Don’t know how well this kind of cheap unit works, but you could always confirm/calibrate it on a known good motor or transformer.

Should any of these tests indicate an anomaly inside the generator, I’d be tempted to pull it and turn it over to a motor rewind shop. There must be some in Brisbane. A rewind/rebuild might be more economically attractive than a replacement of the whole genset. The problem might even turn out to be something simple like a carbon dust buildup that could be pressure-washed out with solvent.

However, if you feel a need to buy a brand-new genset anyway, it’s your money. I just wish I were based in Australia so I could help you “dispose” of the NL.

The Onan waveform was not a good sine wave. In fact it looked very much like the Northern Lights waveform in that is was markedly square. It did however, have a much lower 3rd harmonic and a THD of 22% versus 39% for the NL. The other interesting thing about the Onan, is you can see the effect of the electronic frequency control, as it repositions the sine wave horizontally a couple of times a second to keep the frequency in line. I doubt there is anything wrong with that, but it was quite visible on the scope.

The Westerbeke was better than the Onan. It had a much cleaner sine-wave. There was still some squareness to the wave, but markedly less. THD was 15% for the Westerbeke and it had no trouble running the compressor. I expect that the larger size 7.6kW for the Westerbeke vs 5.0kW for the Onan is the main reason for the better performance, although the Westerbeke is a brushless alternator and the Onan and NL are both brushed, so that may be a factor.

The Westerbeke had essentially no 3rd harmonic, and the Onan was quite low 3rd harmonic, but the NL has a very high 3rd harmonic on all load types. If I was to continue down the troubleshooting path with the NL, I would focus on finding what is causing this 3rd harmonic anomaly. I would bet that it's due to a fault in the windings, or some other internal component within the NL backend, but I have no confidence that removing it from the boat and giving it to a rewinder, would solve anything. If NL was here locally, I would happily let them take the genset off the boat to repair, but that' s not possible.

Regarding the Brushes, the NL support folks in Seattle said that based on the waveforms, the brushes are fine. As for winding resistance, if it's a winding problem then I would prefer replacing the genset rather than dealing with that. The cost to pull the generator out of the boat alone is astronomical here.

We are about to leave for an 18 month voyage around the South Pacific, I don't want to deal with the uncertainty of a malfunctioning, or poorly repaired genset. I was very impressed with the design and operation and low noise level of the Westerbeke so I am going to install it in place the Northern Lights.

[transmitterdan]

It sounds like you have considered everything and have a plan. Good for you and I think you will be happy with the WB.

Next part may be technobabble so feel free to ignore:

Third harmonic distortion of the voltage waveform does not necessarily signify a fault with the generator. In fact, it may be normal. Harmonic distortion of odd order indicates that the waveform is distorted in a symmetrical manner. In other words, it means the upper and lower half of each cycle are equally distorted. On the other hand even order harmonics (2, 4, 8, etc.) indicate something is not equal with the upper and lower half cycle. These are more worrisome. That's why NL is saying the brushes and diodes are probably ok based on seeing the waveform.

I suspect there is nothing wrong with your NL generator. It simply cannot deliver the peak current demand of the VFD. Most likely it has been that way since new. Consider not just giving the gen set away for nothing. Someone will be glad to get it. Based on past experience with this model I would be happy to have it but I am 10,000 miles away.

Fair winds and say hi to the clown fish...

[downunder]

Give Sea Wasp a call. Sea Wasp Marine Diesel Generators Silent Honda Portable Generator Sets

They manufacture their own as well as retail some brands. May be able to diagnose your problem.

SEA WASP AUSTRALIA PTY LTD
Unit 13 / 17 Rivergate Place
Hemmant Qld 4174
Phone: (07) 3907-0708
Fax: (07) 3907-0709
Postal Address
P.O. Box 863
Wynnum QLD 4178

The SEA WASP brand of marine generators has been servicing government agencies, commercial fishermen and pleasure craft for over 30 years within Australia and abroad. SEA WASP marine generators continue to be proudly AUSTRALIAN MADE.

SEA WASP AUSTRALIA has transformed over the last few years to offer customers a full and complete range of marine generators and engines to suit any application.

In conjunction with our qualified Service and Spare Parts Division, SEA WASP prides itself on quality technical advice, installation options and ongoing service of marine engines and generators and spare parts support.

SEA WASP AUSTRALIA distributes the PAGURO range of marine generators offering extremely compact and quite generators to suit the customer who has a confined space to work with. SEA WASP AUSTRALIA proudly represents FPT (formerly IVECO MOTORS) and NANNI Diesel Engines. We strongly recommend POLYFLEX Coupling and Mounting Systems. To compliment our range of generators we also offer HONDA POWER EQUIPMENT – a quality range of small and light weight petrol generators suitable for commercial use or the family camping trip.

[Poozer]

Originally Posted by downunder

Give Sea Wasp a call. Sea Wasp Marine Diesel Generators Silent Honda Portable Generator Sets

They manufacture their own as well as retail some brands. May be able to diagnose your problem.

SEA WASP AUSTRALIA PTY LTD
Unit 13 / 17 Rivergate Place
Hemmant Qld 4174
Phone: (07) 3907-0708
Fax: (07) 3907-0709
Postal Address
P.O. Box 863
Wynnum QLD 4178

The SEA WASP brand of marine generators has been servicing government agencies, commercial fishermen and pleasure craft for over 30 years within Australia and abroad. SEA WASP marine generators continue to be proudly AUSTRALIAN MADE.

SEA WASP AUSTRALIA has transformed over the last few years to offer customers a full and complete range of marine generators and engines to suit any application.

In conjunction with our qualified Service and Spare Parts Division, SEA WASP prides itself on quality technical advice, installation options and ongoing service of marine engines and generators and spare parts support.

SEA WASP AUSTRALIA distributes the PAGURO range of marine generators offering extremely compact and quite generators to suit the customer who has a confined space to work with. SEA WASP AUSTRALIA proudly represents FPT (formerly IVECO MOTORS) and NANNI Diesel Engines. We strongly recommend POLYFLEX Coupling and Mounting Systems. To compliment our range of generators we also offer HONDA POWER EQUIPMENT – a quality range of small and light weight petrol generators suitable for commercial use or the family camping trip.

I'm a big fan of Sea Wasp! In fact Drew from Sea Wasp was the technician that came over to the boat to try and figure out the problem with my generator. They are always very responsive and helpful. I considered their gensets as a potential replacement, but both their own branded sets, and the Paguros are too tall to fit in my generator compartment. The Westerbeke is 20.7" high which will fit in the compartment that holds the Northern Lights.