Some of the most common problems can be avoided by closely following the manufacturer's guidelines for installing and wiring the frequency inverter, such as following proper grounding techniques, using shielded cable where recommended, and routing wiring correctly. Failure to install line-conditioning apparatus (such as line reactors or chokes) where less than perfect plant power is available and running overly long motor leads without adding output impedance correction are factors of which end users should be mindful.

Mounting the frequency inverter in an area that is too hot, cold, or moist, or failure to provide sufficient space around the frequency inverter for proper cooling can also be problematic. Again, following the frequency inverter manufacturers recommendations - and selecting a frequency inverter that provides the right amount of protection demanded by its environment - are key to reducing lost production caused by failure.

Assume 10,000 MW are bid in various state and Centre for Solar PV under Accelerated Depreciation (80% of the project cost will be tax free for a company which has made profit in their other business, which can be seen in AP bidder's list like in Real estate, timber, road, halwai, potato chips, jewelllary, breweries etc) scheme. i.e

Still the Wind and Biomass power projects need government support at the cost of Suicide of Farmers or poor people to whom the Natural resource belongs, but, look at the apathy, how Government has transferred these assets already by paying Rs. 100 crore more that the invested money of Rs. 3250 Crore !!! A kind of hindsight with a future vision for awakening the Policy makers and the stake holders !!

At the bare minimum the 20% increase in specific gravity will call for 20% more horsepower, and most likely the 10-fold increase in fluid viscosity will also require additional horsepower. The assumption being that an increase will take us into transitional flow regime in the Reynolds number vs. impeller drag coefficient curve, where increasing viscosity results in increased drag (power draw) on the impeller. The existing mixer will probably not work and if it does, the mixing will take longer. Here are a few options, some of which may be possible with the tight deadline:

• If mixer is equipped with a frequency converter, or a frequency converter is available, perhaps the mixing requirements can still be met by slowing the mixer shaft draw and shaft speed. The mixer power draw is proportional to the cube of the shaft speed. Therefore a small decrease in shaft speed would result in a noticeable drop in horsepower drawn at the shaft. I estimate that a 7% drop in RPM would be required to account for the increase in density.
• Perhaps the "shear" mixer utilizes a "saw tooth" type (a.k.a Cowles) impeller, which is readily available and relatively inexpensive. A number of vendors can supply impellers quickly. If so, we can take advantage of the relationship between mixer motor draw and impeller diameter — mixer shaft horsepower is proportional to the impeller diameter to the 5th power (D5). A very small decrease in impeller diameter causes a noticeable drop in mixer horsepower; roughly a 4% drop in impeller diameter would be required to account for the increase in density.
• Check with the manufacturer of the high shear mixer. The power frame of the mixer may in fact allow for a larger-hp motor to be put on the machine and still stay within the mechanical limits of the shaft system.

Shear mixers normally are most effective when their impeller peripheral speeds are in the 3,000 to 5,000 ft/min. range. Dropping the shaft speed or impeller diameter would effect the “tip speed” of the blade so if both new impeller and frequency converter are available one perhaps could re-tune the existing mixer to provide the proper process result or at worst case make up smaller batch sizes.

High Voltages in the range of 10kV to 100kV and at low power finds use in a number of industrial equipment such as ionizers. Special electronic circuits are required to generate this high voltage from the relatively lower and safer to handle voltages available. The most straight forward method would be to use a voltage step-up transformer that would convert the lower voltage alternating current on the primary side to a high voltage alternating current on the secondary side. For a compact and lower cost solution, a multi stage voltage multiplier circuit fed by a high frequency AC voltage is used.

Voltage Multipliers
Voltage Multipliers are circuits consisting of a network of capacitors and diode rectifiers. They work on the basic principle of an AC voltage charging sets of capacitors to a peak voltage. The output would be the sum of voltages across a string of such capacitors. The diodes form valves that enable charging in a particular direction and prevent the discharge during the negative of the AC voltage. Voltage multipliers can be used to generate bias voltages of a few hundred volts to millions of volts.

Various types of multiplier circuits, each having a particular advantage, are available. The most simple and common of these is the Half Wave Cockcroft-Walton (CW) Multiplier. The figure below gives the basic schematic for a CW multiplier. This circuit is preferred if the output ripple and voltage drop are not as much critical as the cost and size of the unit.

Before the new product prototype hardware is available simulation is used to complete the design, and work out the kinks in the device. With the introduction of cloud computing simulation has also gotten on board in the test and measurement industry. Considering the fact that development teams for any given product are located all over the world, connecting the puzzle pieces in a virtual environment BEFORE the product is whole allows designers to catch potential problems and fix them, complete design issues, etc. There is no reason why you can't have a simulated part talk to a prototype part of a real world system. Also, when developers are using SCPI capable test gear, the gear itself may operate in a simulated fashion. This is important where several developers share a common expensive test equipment. So in absence of the test gear, the test system may still be able to function albeit in a lower scale capacity.

I started more than 20 years ago using Simulation software connected to PLC's to "Emulate" a system in real-time and use it to verify the PLC code and electro-mechanical design of automation systems used in the manufacturing industry.
Since that time, the term 'Emulation for Logic Validation', also referred to as "Virtual Commissioning", has been to used to differentiate between Simulation and Emulation.

Although a simulation and an Emulation may look to all intents and purposes the same, and may be built largely with the same building blocks or models, there are significant differences in usage and operation.

Simulation models are used to test and develop different solutions in order to arrive at a best solution, based on an accepted set of pre-defined metrics.

Emulation models are not used for experimentation in the same way that simulation models are; they are unsuited to this function as they often execute only in real time.

100% failure is not an outlier in my experience. It may not be mechanical failure, but comms instead. I have seen very close to if not 100% of systems installed have some sort of issue, or multiple failure issues. No one really has the communications side of these things down yet. Communication, or inverter malfunction errors are typical on any micro installation I have seen. The costs of micro inverter versus central inverter replacement and micro service calls are much more expensive. I cannot imagine deploying micros on a commercial scale until a few things happen. The price per unit would have to fall dramatically in order to make up for the increased labor costs, and the communication issues would need to be orders of magnitude better.

We have installed a 140kw micro inverter system and it was at the customer request. The saving grace of the installation is that it is a carport structure and the micros are accessible via an 8' extension ladder. No modules have to be pulled in order to service a micro. I do not recommend micro inverters to anyone looking for more than a kw or so. That is also changing with newer small HF style central inverters with low MPPT ranges. That being said, the customer base Loves micro inverters. Many customers are sold on them before speaking to a sales rep, so someone on the micro side is doing something right! The shading argument is a little off in my opinion and there is a fine line between selling someone a system that has incremental shading, and selling someone a shady system..... System design with a micro can be more simple for a non technical sales person, but it can also lead to poor array placement if left unchecked by the technical support and engineering staff. There is a lot of, oh look a big roof with shade on it, lets use micros inverters happening out there right now. I am in agreement that they have a place in the pv world, but due diligence and robust system design should remain prime drivers on site selection.

Areas with shading, small systems (~5kW) and complex roof geometries are perfect candidates for a micro inverter system. Commercial systems, regardless of how much they are pushed, make no sense if you take ROI and LCOE into consideration in my opinion. Many of the arguments fall apart under the slightest scrutiny- seeing a rooftop full of naked rails with micro inverters attached to them should scare anyone away when looking at all those potential points of failure on a rooftop with no shading.

An outlier with respect to his 100% failure rate could have merit if he wasn't the only one suffering from failures or environmental issues. I was in Las Vegas yesterday and a few installers talked to me about their failure rates in the hot areas of the SW United States. Many micro inverter manufacturers rate their product to 65C ambient, but one installer showed me a FLIR image of the area underneath a micro inverter rooftop installation that read 85C! His micro inverters had been installed for over a year and he had lost a total of 3 MONTHS of production because the inverters disconnect due to high temperatures. This happens more often than people realize in these hot areas.

Each system is unique and its configuration depends of goals - in case when owner is connected to reliable grid and intended just to save some money and maybe sell some electricity, and has not more than 10 panels, then M215 is a good choice.

But if he has not reliable grid, he must have an energy (batteries, for example) storage, a completely different (and much cheaper) of MPPT battery chargers, I would recommend 150 or 300 V strings, and a few cheap synchronized transformerless converters.

And of course he must have some spare converters, batteries and chargers.

And if the goal is just an energy producing, we just throw out batteries and replace cheap chargers with cheap optimizers.

Here will be always lots of questions - for example, (by the way, how exactly) plug strings in parallel or use discrete converter for the each string, how to clean panels in reality, will broken converters just stop energy producing or turn into short circuit, which wires, connectors and insulators will survive climate, where to position converters and other stuff to safe it of lightning, mices, children, how to avoid unnecessary spends, etc. etc. - it is a kind of art.

A failure of a roof-mounted micro inverter requires a much larger effort to replace, compared with a wall-mounted string inverter. I expect the cost differential in labor to replace a roof-mounted micro inverter vs. a wall-mounted inverter would be substantial. This may factor into the overall system availability if a homeowner opts to not replace a single failed micro inverter right away.

I have also heard the opposite case to hold true for certain (primarily government) installs where the budget to purchase the PV system is available, but the budget for O&M down the road is zero. In this case, it is expected that the system output degrades gradually over time with individual component failures, versus a complete system failure should a central inverter fail with no budget for repairs.

I do find this installer's claims of having failures on 100% of their installed microinverter systems to be hard to believe. This seems like an outlier to me, not in line with anecdotal evidence that I am hearing from other installers. However, I'm not an expert in reliability, so I'm not going to get into it.

Inverters main circuit mainly consists of three-phase or single-phase bridge rectifier, smoothing capacitor, filter capacitor, IPM inverter bridge, current limitation resistors, contactors and other components. Many common failures are caused by the electrolytic capacitors. The electrolytic capacitor life is determined by the DC voltage and the internal temperature on the capacitor both sides, the capacitor type is confirmed during the circuit design, so, internal temperature inside the electrolytic capacitor is critical important. Electrolytic capacitor will affect the inverter life directly, generally, temperature increase 10 ℃, inverter life reduce a half. Therefore, on one hand, considering proper ambient temperature in installing, on the other hand, reduce ripple current by taking some measures. Adopt power factor improved AC/DC reactors can reduce ripple current, thereby extend the electrolytic capacitor life.

During inverter maintenance, usually it's relative easy to measure the electrostatic capacity of to determine the capacitor deterioration, when the electrostatic capacity is less than rated 80%, insulation impedance is below 5 MΩ, it needs to replace the electrolytic capacitors.