Subway and generator fail

[agedhorse]

But it worked in April with the exact same generator and loads. Only real difference was the ambient temp. S*** happens, I guess.

Loads are never identical, ambient temperature may affect the generator but I wouldn't by much.

 

[gln1955]

Loads are never identical, ambient temperature may affect the generator but I wouldn't by much.

Lesson learned and thanks for making a robust amp!

 

[seamonkey]

Harbor cruise boat generators can be the worst. When docked they get land power, sound check and everything is good, then before undocking they throw a transfer switch to generator power. It's a new game.

For land gigs, the new style outlet testers with built-in voltage meters are pretty good these days
https://www.amazon.com/KAIWEETS-Electrical-Receptacle-Detector-Indication/dp/B09K46LM69/?th=1
This Kaiweets also includes a neutral to earth measurement, where you would expect to see some voltage difference when under load. The bootleg ground hack can be detected.

 

[Geri O]

For land gigs, the new style outlet testers with built-in voltage meters are pretty good these days
https://www.amazon.com/KAIWEETS-Electrical-Receptacle-Detector-Indication/dp/B09K46LM69/?th=1
This Kaiweets also includes a neutral to earth measurement, where you would expect to see some voltage difference when under load. The bootleg ground hack can be detected.

That’s a great find, but I wonder why it’s nearly a month to arrive once ordered, according to the listing. May spring for it anyway.

The one time I remember doing a cruise was in the 80s on a MS River cruise from Memphis for a high school prom. Once loaded in, the captain, or whomever he was, told us to get set up, then they would disconnect shore power and check our gear on the boat power. Fortunately, it all checked out. The captain person told us they do a lot of those and they’ve seen everything from complete success (as was our event) to total failure. And he didn’t have much confidence in the boat power. He said we were lucky….

 

[agedhorse]

Good quality marine generators are quite good IME.

 

[fdeck]

I played an outdoor gig where they had a small Honda, and the person operating it hadn't read the instructions. As a result it put out some impressive smoke and then packed it in just before we were supposed to start playing.

Turns out there's a reason for reading the instructions. Also, a choke lever. Fortunately we eventually got it running.

 

[lermgalieu]

The story begins back in April. The band has a gig at a public park with no electricity. This is our first time supplying our own power. I'm aware of possible issues with non-inverter type generators, so I offer to bring my Honda, although I'm not sure it would be powerful enough for the whole band. The BL says he is all set up with a brand new generator, so I leave mine at home. I get there and it's not an inverter-type unit. I'm not pleased and tell him the first sign of trouble and I'm literally pulling the plug. Well, everything is fine and we play a four-hour gig without issue.

Chapter 2, we play the same site this week and my D-800 won't power up. Absolutely nothing. I play the gig through a preamp pedal to FOH (which is a miserable experience without adequate monitors) and I'm worried the whole time about a possibly damaged amp. Then I get home and plug the amp in and it's perfectly fine. Dodged a bullet, thanks to some protection circuit, I assume.

I won't be using that generator again, but I'm curious about what exactly happened this time, that didn't happen back in April. The only difference was the gig in April was in about 50F weather and Friday it is was about 90F. Could the high heat cause the amp and/or the generator to behave differently enough to cause the fail?

Calling @agedhorse

If I’m not mistaken, once the D800 goes into protect, you have to let it sit for something like over a minute before it will turn on.

 

[Slevage]

In my gig tool box is a Fluke multimeter that I have used more than once to adjust governors on crappy generators to bring voltages into useable range. Meter and outlet tester are indispensable goodies for the gigging player.

Those are great tools, but they don’t tell you if you have a nice, symmetrical sine wave coming out of the generator.

 

[agedhorse]

If I’m not mistaken, once the D800 goes into protect, you have to let it sit for something like over a minute before it will turn on.

There's a 20 second short-cycle protection delay on all the 800 series amps

 

[agedhorse]

In my gig tool box is a Fluke multimeter that I have used more than once to adjust governors on crappy generators to bring voltages into useable range. Meter and outlet tester are indispensable goodies for the gigging player.

That should be a fascinating exercise since the speed of the engine (and rotational speed of the generator) is generally responsible for the frequency and not the voltage. There are exceptions but they are not all that common. The voltage is adjusted by the exciter winding feedback, which is how the same generator head can develop the same voltage at different frequencies.

 

[lermgalieu]

There's a 20 second short-cycle protection delay on all the 800 series amps

I was a little off

 

[fdeck]

There's a 20 second short-cycle protection delay on all the 800 series amps

That's the reason for "no shorts on stage."

 

[Playbyear]

That should be a fascinating exercise since the speed of the engine (and rotational speed of the generator) is generally responsible for the frequency and not the voltage. There are exceptions but they are not all that common. The voltage is adjusted by the exciter winding feedback, which is how the same generator head can develop the same voltage at different frequencies.

Absolutely, the speed of the engine/ generator determines frequency. Most small non-inverter generators have a 2 pole generator turning at 3600 RPM for 60 HZ output.
Yes, voltage will typically increase and decrease with speed, but it’s not how you would set the voltage output.

(and rambling on here...)
Most of these small non-inverter generators have very crude voltage regulation. Often just using a capacitor for regulation. That combined brush type excitation, not the best build quality and the output can be quite dirty.

then you have the small engine itself that typically runs inconsistently. How many lawn mowers , snowblowers, etc... run consistently all season?

modern larger generators will have true automatic voltage regulators, brushless excitation, and are engineered and built to supply clean power.

A cruise boat should have a good generator and clean power, at least when it was new. Poor maintenance and wiring can certainly comprise that.

 

[SemiDriven]

Inverter generators typically have an Eco mode, which is intended to save fuel by running the engine at the lowest possible RPM required to meet load requirements. Since music is dynamic, the current and power requirements for a big PA tend to change constantly. The motor cannot respond quickly enough to cover the required transients, so Eco mode should not be used for live music support.

At our outdoor gig yesterday, the venue provided a small, Honda generator with an Eco mode option (so I'm assuming it was an inverter generator).

Eco mode worked for our band power needs and the Subway 800+ performed flawlessly.

I was kinda floored how quiet it was (and fume free).

I was surprised how heavy that lil' sucker was -- took two of us to move it around!

 

[Ewo]

For land gigs, the new style outlet testers with built-in voltage meters are pretty good these days
https://www.amazon.com/KAIWEETS-Electrical-Receptacle-Detector-Indication/dp/B09K46LM69/?th=1
This Kaiweets also includes a neutral to earth measurement, where you would expect to see some voltage difference when under load. The bootleg ground hack can be detected.

That item is out of stock, now. This looks pretty much the same. Has a reading for neutral-to-earth.

https://www.amazon.com/Receptacle-D...d_r=a1723898-8309-4115-ad7a-f8007dfc70df&th=1

 

[Sparky Mark]

That's the reason for "no shorts on stage."

Shorts are okay, just leave the socks with sandals backstage!

 

[spankdaplank]

Things I learned about generators the hard way: Living here in the Philippines with blackouts and weather, I have a diesel generator of qustionable quaulity. Two years ago we were hit with a 168mph typhoon resulting in a two and a half MONTH blackout.. As a result I had to quickly school myself on small generators. The ironic thing is, I am a retired powerplant electrician. Our original generator failed with a blown engine so we somehow were able to get aanother one despite all generators already being sold. I found out later-too much later that the new one operated at 50hz which is China's standard. Our refrigerator compressor and our water pump motor were destroyed. The UPS in my studio would not fire up to recharge. I wrongly thought it was low voltage caused by overload on this 5KW generator. So here is what I discovered through careful troubleshooting and research: The frequency can shift 10 or 15 % or more with saging RPM's. Iwas never able to get 60hz by speeding up RPM's. Under the dust cover on the end of the generator unit there is usually a semi circular potted electronics. There will be an exposed trimpot on it that is the voltage control. So with a multimeter with a frequency function and a way to load the generator, the balance between frequency/engine rpm controlled and voltage can be zeroed in. The problem with the whole arrangement is that under sudden load there is a signifigant lag as the engine govenor reacts, so the frequency sags too. Some electronics seem immune while other loads are subject to catastrophic failure especially at prolonged exposure. I'm guessing anything with a transformer or an induction motor is at serious risk
Now you know. Indeed generators can kill.

 

[agedhorse]

Generally a 50Hz generator can be run at ~17% increase in speed (assuming that the 50hz generator's engine is running at 3600 x .83 = 3000 rpm) or if it's belt drive then the pulley ratio will need to change. A 2 pole generator is a 2 pole generator, the frequency is based on the RPM be it 50Hz or 60 Hz. A 4 pole generator will run 50% slower for the same frequency. Once the RPM is set via governor adjustment, the excitation current is set which adjusts the voltage. The curve of the excitation current must match the losses of the generator for the regulation to track from no load to full load. It's very much like how global feed back in amplifiers works.

Generally, for a reasonable gen set, the reduction in RPM doesn't affect voltage as much as frequency because of ecxitation current that provides regulation. Motors and line frequency transformer loads are more sensitive to frequency, switchmode power supplies are not.

There are some generator topologies that are self-exciting, self-regulating or capacitor excited, where when the rpm decreases the voltage will in fact change along with the frequency. This is getting into the weeds though, and it's been several decades since I worked in that field regularly.

 

[spankdaplank]

Generally a 50Hz generator can be run at ~17% increase in speed (assuming that the 50hz generator's engine is running at 3600 x .83 = 3000 rpm) or if it's belt drive then the pulley ratio will need to change. A 2 pole generator is a 2 pole generator, the frequency is based on the RPM be it 50Hz or 60 Hz. A 4 pole generator will run 50% slower for the same frequency. Once the RPM is set via governor adjustment, the excitation current is set which adjusts the voltage. The curve of the excitation current must match the losses of the generator for the regulation to track from no load to full load. It's very much like how global feed back in amplifiers works.

Generally, for a reasonable gen set, the reduction in RPM doesn't affect voltage as much as frequency because of ecxitation current that provides regulation. Motors and line frequency transformer loads are more sensitive to frequency, switchmode power supplies are not.

There are some generator topologies that are self-exciting, self-regulating or capacitor excited, where when the rpm decreases the voltage will in fact change along with the frequency. This is getting into the weeds though, and it's been several decades since I worked in that field regularly.

What you said is 100% accurate. Just to be clear this generator was sold to me in the middle of a disaster and was manufactured as a 50hz unit even though the grid is 60hz here. In my real world experience dealing with this POS Chinese generator, and with me under a lot of pressure to make it work, I found out that I could not increase the RPM's high enough to get above 56hz or so. Unfortunately I did not have a tachometer. Anyway the internal goveror ran out of adjustment and the single cylinder diesel (junk) was crying for it's life. Like was said the voltage output change was relatively small and could be adjusted regardless of engine speed with the the trimpot on the voltage regulator. Of course it was a real challenge to land the tiny screwdrver into the slot on that trimpot with the unit vibrating like crazy. LOL
P.S. I had to set it back to 50hz as the engine was definitely going to self destruct at any higher RPM.

 

[agedhorse]

What you said is 100% accurate. Just to be clear this generator was sold to me in the middle of a disaster and was manufactured as a 50hz unit even though the grid is 60hz here. In my real world experience dealing with this POS Chinese generator, and with me under a lot of pressure to make it work, I found out that I could not increase the RPM's high enough to get above 56hz or so. Unfortunately I did not have a tachometer. Anyway the internal goveror ran out of adjustment and the single cylinder diesel (junk) was crying for it's life. Like was said the voltage output change was relatively small and could be adjusted regardless of engine speed with the the trimpot on the voltage regulator. Of course it was a real challenge to land the tiny screwdrver into the slot on that trimpot with the unit vibrating like crazy. LOL
P.S. I had to set it back to 50hz as the engine was definitely going to self destruct at any higher RPM.

It may self destruct at any speed above 0 RPM too

Direct drive diesels are generally 4 pole generators and operate at 1800 RPM for 60Hz and about 1500 RPM for 50Hz.

I'm restoring an old belt drive WW-II signal corps generator right now, just a hobby thing with no practical value, it's a brush type generator with a commutator and slip rings. It would cost a million dollars to build like that today.