50Hz 230 volt power in a 60Hz world

[iceworm]

Which can be replicated using solid-state power electronics.

Of course. But not nearly so elegantly.

Sometimes a low-tech, simple solution is the best.

Then again, if anyone could point to a 5Kw - 7.5kw VFD with an output into 0% - 100% full load that is\will:
sine wave output with THD <3%
supports Crest Factor of 3:1
support minimum Power Factor(Leading/Lagging) of 0.65 (either direction of power transfer) I'll let that one slide to .8pf

and has a regenerative front end.

And off-the-shelf would be nice - don't really want a custom built unit.

Now that would be an equally elegant solution.

ice

 

[iceworm]

Yes you did - in post 2. Sloppy me. I try to catch and credit all of these.

In my defense, I didn't see the concept of coupling a synchronous 10 pole gen to a synchronous 12 pole motor to capture the 50/60hz conversion, nor the idea of running the power transfer bi-direcction to both cover the stable 50hz source to allow the micro inverters to start as well as provide a load dump for the micro inverters that seamlessly transfers the power to the 60 hz utility.

ice

And credit to hurk in post 36. My thoughts are just a refinement on his

ice

 

[Besoeker]

Of course. But not nearly so elegantly.

Sometimes a low-tech, simple solution is the best.

Then again, if anyone could point to a 5Kw - 7.5kw VFD with an output into 0% - 100% full load that is\will:
sine wave output with THD <3%
supports Crest Factor of 3:1
support minimum Power Factor(Leading/Lagging) of 0.65 (either direction of power transfer) I'll let that one slide to .8pf

and has a regenerative front end.

And off-the-shelf would be nice - don't really want a custom built unit.

Now that would be an equally elegant solution.

ice

An output THD <3% and a crest factor of 3:1? You can't have both

Anyway, it rather depends on what you want to do. Or, maybe not so much.
A 50Hz output that you want to load by sticking it back in a 60Hz utility?
Or vice versa?
The facility to load one or the other with additional passive loading?
The ability to cope with the full range of power factors?

Here's one we made earlier (to paraphrase that expression sometimes used on cooking shows....)

One end is designed for power flow in either direction at 50 or 60Hz. The other can do the same. Or at any other frequency.

Admittedly it's a bit more than 7.5kW and has a few bells and whistles to provide control functions for the specific application. But all the parts are standard parts. Even the steel enclosures - apart from the top hat arrangement for ventilation.

I agree that a rotary set would be simpler in principle. More or less expensive? Don't know. More or less efficient? Without a shadow of doubt, the static solution is significantly more efficient.

 

[iceworm]

An output THD <3% and a crest factor of 3:1? You can't have both ...

Let me define crest factor for power supply applications: (APC white paper 17 - not that APC is great, just an easy place to grab a definition)
Crest factor
In addition to a low power factor, some computer loads are also unusual in that they exhibit a very high crest
factor. Crest factor is the ratio between the instantaneous peak current required by the load and the RMS
current (RMS stands for Root Mean Square, which is a type of average). Most common electrical
appliances exhibit a crest factor of 1.4 (1.4 is the ratio of the peak value of a sine wave to its RMS value).
Computers and IT equipment with Power Factor Corrected power supplies exhibit a crest factor of 1.4.
Personal computers and stackable hubs exhibit a crest factor of 2 to 3.

So THD is a measure of how close the voltage wave form is to a sine and Crest Factor is a measure how well the power supply can supply current to a non-linear load.

I think I can spec both.

ice

 

[Besoeker]

Crest Factor is a measure how well the power supply can supply current to a non-linear load.

So, in the context of this thread, what non-linear load is being supplied?

 

[iceworm]

So, in the context of this thread, what non-linear load is being supplied?

To my admittedly limited understanding - higher crest factor capability means the supply can better keep the THD low, keeps the output closer to a sine wave.

However, likely none of this matters:

This thread has a context? Conception, design, and construction is in Dreamscape?

You like a different set of specs?

Okay

ice

 

[tallgirl]

Of course it isn't economical - that was covered several posts ago. The project can't even afford a battery bank.

I don't believe "afford" was the issue. Batteries are their own headache. Never underestimate the desire to avoid headaches!

 

[Besoeker]

To my admittedly limited understanding - higher crest factor capability means the supply can better keep the THD low, keeps the output closer to a sine wave.

Crest factor is often a term used for UPS specifications - the ability to cope with non-linear loads.

You like a different set of specs?

Nope. Just explaining what can be done with standards bits.

 

[iceworm]

I don't believe "afford" was the issue. Batteries are their own headache. Never underestimate the desire to avoid headaches!

I tend not to do that. My usual philosophy is "throwing money at a maintenance issue and making it go away, is generally a good idea".

So, I already gave you an idea on how to ditch the batteries, substutiting a near zero maintenance device. If the project is economically viable - look at using them.

No I'm not going to remind you. This is a test to see if you read actually read the posts.

ice

 

[iceworm]

Crest factor is often a term used for UPS specifications - the ability to cope with non-linear loads. ...

Yes, that's true --- --- --- and your point is?

Oh, are you wondering why I would use a spec normally used for UPSs in this conversation?

ice

 

[Besoeker]

Yes, that's true

Glad that you don't dispute it.

and your point is?

Is a UPS spec relevant in the context of converting power at one frequency to another totally reversibly?

Oh, are you wondering why I would use a spec normally used for UPSs in this conversation?

Am I? Don't think so.

 

[iceworm]

Is a UPS spec relevant in the context of converting power at one frequency to another totally reversibly?

Well, "a UPS spec" may not be relavent, but this specific one is. The outputs are power supplies, need to be close to sinosoidal, don't know what the loads are, I chose to cover non-unity power factor and non-linear loads.

If the power electronics can't handle that, it's okay with me - you are free to choose a diferent spec.

If they can handle that, what is the question?

Oh, are you wondering why I would use a spec normally used for UPSs in this conversation?

Am I? Don't think so.

Yes, you are.

Is a UPS spec relevant in the context of converting power at one frequency to another totally reversibly?

And that last statement translates as you are wondering/questioning.

I wouldn't have mentioned it, but it seems important to you to not be seen as questioning or complaining about the spec. I don't understand that - but that is okay that I don't. Truly, it is okay.

ice

 

[tallgirl]

I tend not to do that. My usual philosophy is "throwing money at a maintenance issue and making it go away, is generally a good idea".

So, I already gave you an idea on how to ditch the batteries, substutiting a near zero maintenance device. If the project is economically viable - look at using them.

No I'm not going to remind you. This is a test to see if you read actually read the posts.

ice

I'll have to look into that -- the problem with the ultracapacitors that I've looked at in the past is capacity. Thanks for giving me an excuse to look at them again

 

[iceworm]

I'll have to look into that -- the problem with the ultracapacitors that I've looked at in the past is capacity. Thanks for giving me an excuse to look at them again

Not the little ones from digikey, allied, newark, rather there is an outfit in Canada selling 24V, 100F (? or so) for starting trucks. That was a couple of years ago, and I never got to get one either. I don't know if they are vapor or not. I never talked to the company.

ice

 

[Besoeker]

Well, "a
And that last statement translates as you are wondering/questioning.

It was a rhetorical question.

 

[tallgirl]

Not the little ones from digikey, allied, newark, rather there is an outfit in Canada selling 24V, 100F (? or so) for starting trucks. That was a couple of years ago, and I never got to get one either. I don't know if they are vapor or not. I never talked to the company.

ice

100F isn't enough, though I know how to put capacitors in parallel

A Farad is, from fuzzy memory, a Coulomb-sec per Volt (and really -- fuzzy memory, I'm lucky if that's even close). Inverters have relatively more narrow voltage ranges than vehicle starter motors. That's a large part of why lead-acid batteries work as starter batteries. The voltage depression under heavy load is tolerable to the motor.

 

[Besoeker]

100F isn't enough, though I know how to put capacitors in parallel

It's a huge capacitor but I've seen some claims claims about ultra capacitors that put them in that region. But I agree, it isn't enough.
The energy stored in a capacitor as I'm sure you know is ¹/₂CV².
Or about 28,800J at 24V. A tiny fraction of that stored in a starter battery. Or the equivalent of about 100W of lighting for under five minutes.

A Farad is, from fuzzy memory, a Coulomb-sec per Volt (and really -- fuzzy memory, I'm lucky if that's even close).

It's Coulomb/Volt. The Coulomb already has seconds in it's definition.

That's a large part of why lead-acid batteries work as starter batteries.

Or maybe just that they are cheap compared to alternative energy storage technologies capable of performing the required task?

 

[GoldDigger]

100F isn't enough, though I know how to put capacitors in parallel

A Farad is, from fuzzy memory, a Coulomb-sec per Volt (and really -- fuzzy memory, I'm lucky if that's even close).

Almost. Since charge = C x V, the unit is Coulomb per volt. Or alternatively (Coulomb per second) per (volt per second) which relates I to dV/dT.

A physics student I knew was asked by a teacher to estimate the capacitance between two parallel 1" wires, 1" apart. He guessed "Two?" The teacher than asked him "Two what?". Fortunately he remembered what the unit of capacitance was, but unfortunately he had no idea of the scale and replied "Two Farads!" Correct answer is about two pico-Farads.

 

[Electric-Light]

You can forget super capacitors for now. The engine starting capacitor bank is used like the capacitor in a camera flash or a toilet tank.

The lithium ion battery holds enough energy to power the flash like 100 times, but not enough rate of power delivery to do so. The internal electronics trickles power into the bucket (capacitor) which dumps it into the xenon tube. With each flash, the bucket is refilled.

http://www.cantecsystems.com/ccrdocs/cantec-can-crank-12pp-50.pdf
14.2Wh and 0.35Wh/kg. This thing weighs 100 lbs and holds the same amount of usable energy as three Energizer Lithium AA batteries. Regular lead acid battery holds about 35Wh/kg in contrast.

http://www.cantecsystems.com/ccrdocs/cantec-can-crank-properties-and-performance-analysis.pdf
Look at page 13. (0.9)^2 = 0.8, so after just 5 hours, it loses 20% of energy charged.

Mechanical storage offers the highest storage energy density for stationary applications. These flywheel UPS basically uses huge rotors suspended on magnetic bearing in vacuum spinning at something like 100,000 RPM. It charges up with a motor and extracts the energy via a generator.

 

[iceworm]

When the EE's were originally setting up the testing system, my proposal was a quad stack of OutBack gear -- a twin stack of 50Hz grid-interactive inverters, and a twin stack of 60Hz grid-interactive inverters, with batteries in the middle. Controlling the output of the 50Hz array with a contactor, with the coil power from the 60Hz grid, would have been fairly easy.

...but my understanding is that the batteries were the deal-breaker. ...

...Your suggestion that the power be converted on a DC bus is what I'd suggested -- some vendors inverters can be AC coupled (one inverter backfeeding the output of another) and that can be used for frequency or voltage conversion. Stick batteries in the middle and DC output of one AC coupled inverter can be DC coupled to another with a completely different frequency system.

...DC coupling refers to connecting two different inverters via a DC bus, typically with batteries on the bus as well to provide a stable DC supply. ...(

From these posts, I was understanding that the batteries were not particularly for energy storage. Any power provided from the 50Hz micro-inverters was to be immediately sent out to the 60Hz grid. The issues appear to be stabilazation of the DC bus. my translation is a low impedance is required to allow high power transfer. Please note that I said "power" not "energy".

I don't believe "afford" was the issue. Batteries are their own headache. ...

And, of course, battery maintenance

100F isn't enough, though I know how to put capacitors in parallel ...

As Electric-Light graciously provided, the 12v units are 879F. I can't tell if you need 12V, 24, 48, 120VDC

...But I agree, it isn't enough. ...

You can forget super capacitors for now. ....

If you are comparing specific energy storage, Caps to WLA batteries, you are correct WLAB are much higher. But, from my interpretation of the limited information that is not the issue. As I mentioned earlier, it appears to be a source impedance issue.

So, I'm curious, how is it you know that the ultra-caps are not enough? And not enough of what? What spec are you looking at?

And, you could well be right - I don't know enough about the project specs to make any kind of determination

ice