Iacdrive|Automation Solution

Generator reactive power

After the generator connected to grid, the generator will be more stable than before connected to grid, because in this situation the frequency and voltage are fixed and controlled by the grid, not the independent generators. How much active and reactive power you can contribute to the grid depends on the grid requirement, such as when the grid shorts of active power, the frequency of the grid will drop, and then the grid will ask you or other generators to contribute more active power, and if short of reactive power, voltage will drop, then you could be asked to contribute more reactive power, and vice versa, which depend on the balance of power which is generated from generators and consumed by the users.

From generator side, the less reactive power, the better, as this power increase the VA and then the current to increase the losses on the transmission line which will be carried by the plant. But from grid side, as not too many equipment can generate the reactive power, the more contribution of the reactive power, the better.

At the full load operation of generator, the maximum contribution of reactive power should depend on the PF of the generator at full load (manufacturer provided for each generator). If your PF is too low and it could affect your active power transfers to the grid and will be punished by the grid. At the not full load situation of the generator, the PF could not be decided by the generator, if the grid does not need too much active power from you, but needs more reactive power and asks you to contribute more, PF could be more than 1 at the moment, but never over the Max reactive power calculated from full load.

Solar power

On a purely theoretical level and ignoring interrelated economics and energy usage, it makes sense to charge EVs during the day – though never in non-distributed environments, IMO.

In reality, and the reality for likely the rest of my life, it makes more economic and particulate emissions sense to distribute solar power during the day to decrease, and ultimately decommission, fossil fuel sources used for peak demand supply that occurs during the day.

Thus, using solar output distributed to offset the dirtiest, most expensive and most distribution grid loading power enhances and optimizes the value and worth of that solar generated power – both economically and ecologically. Attempting, therefore, to do all of ones’ EV charging off peak is the optimal solution until the mix of energy sources changes dramatically – likely a 20 plus year process even in the most environmentally friendly “energy generation mix” regions of the world. Even if one charges during “peak”, it is better to simply charge from the grid as the distributed energy is allowed to go to areas of peak demand. Again, for at least my lifetime, I don’t project a more optimal use of that generation even assuming the archaic state of most “grids” persist.

Right now, even for a 1 story commercial building, solar cannot supply the energy needs used in the office, much less a manufacturing facility. In fact, it can normally only supply 1/3 or less for the most energy and resource intensive commercial environment in a UV intense region (and that is quite an optimistic calculation, more likely 1/5th). Once you get to two or more stories on the building, one is not even close. On a modest tower with a tower parking garage, the footprint is likely to small to even generate the needs on a theoretical basis. Distributing the energy to location of greatest needs will allow us to dial down and decommission peak sources, which again are the dirtiest and most wasteful.

At some point, we will hit a new equilibrium where the energy generation mix is much cleaner, solar generation specifically is much more efficient, and peak power generation is handled more efficiently and ecologically cleaner. I still believe, however, that distributed power is better than “off grid” type of scenarios as it allows the energy to go where it is being demanded at the moment, decreasing the need for redundant sourcing. And, even in the cleanest energy generation mix, redundancy means building more of something and is by definition more energy wasteful and ecologically wasteful than a scenario where the redundancy buffer that is required is lesser.

Much of this type of debate reminds me of the consumer sort recycle versus the destination sort recycle debate. Even with the advances in trash collection and recycling processes, 20 years later we are suboptimizing the recycling process. Much of the reason for that is the “style” statement, making people feel like they are contributing by sorting themselves. It may make some people “feel” better by imagining “independent” off grid or semi off grid solutions. In reality, however, we live in an interconnected world where “sharing” or distributing solutions to leverage scale and minimize redundancies is far more advantageous, economic, and a faster route to a solution to both particulate emissions issues and energy independence for groups of people.

Cleaning solvent for motor windings

Usually, the dry ice approach is the best bet because it leaves no real residue from the cleaning material. If the insulation is “fluffing”, the likely problem is that the air pressure used to move the dry ice particles is too high.

A second alternative that can be used is “corn cob blasting”. The media is reusable, biodegradable particles of corn husks. Again, a relatively low pressure air stream is required. It WILL damage the insulation if the pressure is too high, just as in the dry ice case.

Most solvents will aggressively attack the insulation systems used for windings: this is specifically true for the larger machines where mica tapes are coated / filled with a resinous material (vacuum pressure impregnation). However, it is equally true for smaller machines where the primary insulation is at the strand level and is essentially a varnish or enamel coating on the wire. If you’re worried about how the solvent will affect the insulation system, get in touch with the motor supplier for their suggested approach.

If a solvent-based cleaner must be used, it should be applied sparingly – BY HAND – on the areas to be cleaned to break up the oily / greasy contaminant and then rewashed with some other (non-solvent) approach to clean away any solvent residue. This also will require a “dry out” of the equipment after the second washing. This three-stage approach tends to minimize damage done by solvent that may be left behind to “eat away” at the varnishes, enamels, and resins comprising the insulation system.

One last thing – pretty much ALL solvents are going to be designated as hazardous materials in most regions, due to health concerns. Therefore it is more a case of “pick your poison”!

Negative Impact of Accelerated Depreciation on the Indian Economy

For argument sake or as an illustration, if we assume that 1 MW solar will generate 1.6 Mkwh and rs. 1.2/kwh is rebate for AD taken by the investor = 16 x 1.2 = Rs. 19.2 lakhs/year

[Now, Adani and Tata Power have been negotiating the firm Contract PPA to get more, like wise biomass people who based their PPA on LCOE, but, are asking more money from Government, hence, Solar PV developers may also follow the same route after few years, wherein this rebate of AD given will not have any meaning!!]

Total rebate given = 19.2/year x 25 years = Rs. 480 lakhs = Rs. 4.8 Crore (that too year wise depreciated / devaluated rupee value, which has no meaning !)

But, the tax saved is = 80% of investment = 0.8 x 10 cr = 8 Crore, upfront, right in the first year, which is great value, which government would have used as Equity to develop many more MWs.

Is this POLICY of providing 80% Accelerated Depreciation correct by any standards and why Finance Secretaries or policy makers can’t take note and issue corrective measure for INDIA FIRST Culture??

MNRE, in its Draft policy has proposed 20 to 40% Viability Gap Funding, which will further worsen the LOSS to the government !!

If Mahagenco (with 50% subsidy) goes ahead with the proposed business model, then, how and why State and hence Central government has to take the burden due to such errant policies??
We must put an end to the Scrupulous Project Development, which avails the Capital Subsidy (or Viability Gap Funding) and the Accelerated Depreciation and then the Promoters Sell the Project to a prospective buyer, who in turn approaches the Government for the Tariff hike in the 25 years tenure (please note the Politics dynamics or change of administrative set up will hamper the sustainability), thus, the nation is a great loser

Policies and the enabling tax advantages to few promoters (who claimed Capital Subsidy without creating good quality asset or with NON functional biomass power plants) have made a big dent on Indian Economy without any good results esp in Renewable energy sector.

Government or its administration through such policy (without checks or being accountable) transferred the Public Property to the Private Companies in the Form of Renewable Energy Generation through Capital Subsidy (or Viability Gap Funding) coupled with Accelerated Depreciation along with Low cost Debt fund to these Corporate companies (like EXIM etc) / Project Developers – entrepreneurs, which are not paid back as few of these projects are not functioning and still no action taken to recover the Capital Subsidy paid or Tax recovery which was availed through Accelerated Depreciation (AD).

If Government would have established all these projects from the Tax collections (which are doled out as free through AD), it would have needed only a fraction i.e only Rs. 51,504 Crores, which could have been managed from the taxes of Rs.137,344 Crores while retaining the land and property in Government’s name and could have generated lot of employment.

But, by giving an opportunity to Private sector, many have failed to deliver and no Action to recover the Capital Subsidy or the Debt (due to Tribunals etc…. Please be informed that Indian Parliament had to pass an act in Dec 2012 to recover debt (through wrong business cases of Project Promoters, approved by many banks which were certified by National and International Advisors or Consultants) which is around a whopping 40 Billion USD!!)

Total estimated Renewable energy project capacity = 12% of total installed 220GW = 26000 MW
Cost/ MW Investment Equity Debt Cap Sub AD
Source MW installed Total 30% 70% Rs(Cr) 80%adj
Biomass 6 4,500 27,000 8,100 18,900 6,750 21,600

Wind 7 20,160 131,040 39,312 91,728 104,832

Solar PV 10 1,300 13,000 3,900 9,100 VGF? 10,400
(Ground)

India renewable energy

Refer to the REI seminar, wherein Government of India representative stated that the VGF payment is spread over 5 year period.

1) Any profit Making Company, must have had the benefits from the Government (subsidies etc) / Eco system.

The profit must be taxed for the improvement of the Economy of the Country.

2) Present renewable energy policy is allowing these profit making companies to avoid paying taxes, and own the assets due to such FREE EQUITY, which belongs to the Government, thus Accelerated Depreciation (AD) is a killer of Economy.

Thus, we are unable to develop the NICHE technology as unrelated industries are owning the project due to avoidance of paying taxes and just to own the assets due to such loop hole in the policy, later making an early exit to make quick money without serving the Nation.

AD promotion is not a level playing field apart from Tax loss to the Government.

3) The Tax thus saved, is again allowed to earn 19 to 24% Return On Equity (ROE), which is very unfair (actually this should have been disallowed to have rs.3/kwh less tariff), due to a fact that, this is public money, hence, should not be allowed to have such wind fall gains.

4) By loading ROE, showing high CAPEX and taking back more than 30% project equity, getting EXIM Bank or such low cost funding to reduce the interest burden, but, Tariff claimed of rs.18 or 15 or 10/kwh is once again a kind of Tariff subsidy, thus, a common man is paying more money for RE power tariff, which is a great killer of economy and making people poor.

5) Viability Gap funding in addition to AD will be an Economic suicide as a project promoter will be allowed to take back 60 to 70% of project cost without paying tax on profit earned !!

This is likely encourage poor equipment buying / its maintenance due to such immediate undue / windfall gains.

6) Despite taking such huge wind fall gains, again these project promoters will be allowed to sell the project to others, to make further wind fall gain to make few existing companies to get undue benefits due to such wrong policy guidelines, despite many representations made to the Government, which states that they have go clearance from Finance Ministry to further ruin the Economy !!

What is SynRM motor?

Many others thirty years ago, synchronous reluctance motors (SynRM) have finally replacing the traditional AC induction motors in the industry. ABB has claimed achieving IE4 efficiency with SynRM, a great improvement from IE2 efficiency with the traditional induction motors, for the same motor envelope size and input power.

A SynRM is a true AC machine with or without permanent magnets on the rotor. It is totally different from the closed-loop controlled, permanent magnet brushless DC machines (BLDC) in that one would never be able to get rid of torque ripples as that have been achieved in commonly used BLDC machines.

The difference is on the rotor: copper or aluminum bars for inductance motor (squirrel cage after joining end disks) vs. flux barriers (air pockets) in SynRM. The SynRM rotor can be further enhanced by inserting permanent magnets in the air pockets for a machines called PM assisted SynRM. High efficiency is achieved for two reasons: 1) no copper loss due to the lack of rotor bars and end disks; and 2) high inductance difference between d- and q-axes (Ld-Lq) because of flux barriers and motor torque linearly proportional to (Ld-Lq).

In comparison with the traditional AC induction motor, a SynRM motor needs a frequency inverter and when permanent magnets are present in the rotor, a rotor position feedback sensor. The drawbacks of SynRM are the motor torque ripples due to switching operation, inherited small air gap, etc.

Can I operate a 50Hz transformer at 60Hz power supply?

Well first let get one thing straight for transformers: the higher the line frequency, the lower the core (iron) losses! The core power loss are proportional to kf*B^2 approximately for any machine, dynamic or static. But transformers are self-excited static machines, meaning the flux density B is reverse proportional to the line frequency, therefore Pcoreloss = kB^2*f=k*(1/f)^2*f=k/f… so the higher f, the lower the losses. However, increasing the frequency also increases the magnetizing inductance – lowering the magnetizing current. For if you increase the frequency you may want to increase the voltage. But of course this is not usually practical, as line voltage of 60Hz systems is usually lower than those of 50Hz systems. So operating a 50Hz motor at 60Hz should be safe, but may result in higher voltage drop because of lower magnetizing current and because of higher leakage inductance (the series inductance).

It is true that the higher the frequency, the higher the hysteresis (and eddy current) losses will be. But is it a common misconception to assume higher power losses when frequency increases in a transformer. Simply because the hysteresis losses depends not only on frequency, but on the max magnetic flux density as well (Bmax^2). The flux density is reversely proportional to the line frequency, which eventually causes lower core losses as you raise the frequency. This holds true for low and mid frequency ranges. For higher frequencies, skin effect and eddy currents dominates, so the picture may be different. However, iron core transformers do not operate in such high frequencies. We use ferrite core instead. In a practical transformer model, the core losses are represented by a parallel resistor (Rc). The resistor’s value is linearly dependent of the line frequency (Rc=k*f), and the core losses are given by Pc=U^2/Rc… Of course this model is limited to mid-low frequencies…

Electrical drives for off-highway vehicles

I’ve seen some attempt of electrical driven prototypes in the field, but is still not an enough big sector that let you find specific literature. Excluding the large dumpers for mining, probably the only machine that is built in series is D7E from CAT.

One of largest engineering challenge that you will face on a similar application, is the cooling to the power electronic. You can consider that you will have to dissipate 3-5% of the power that your driver is processing and the max temperature of IGBT’s is not so far from the max temperature in that your vehicle can operate. A small temperature delta, mean a large heat exchanger and/or pretty high speed of air through it. (That with all the problems related to that). A possible solution is liquid cool the IGBT’s mounting them on the aluminum plate. You can’t use the engine cooling fluid because it too warm, but you may can use hydraulic oil (that should never get warmer of 55C).

If you are thinking to expand some gas from the AC, please take in account the possible condensation issues (your voltage on the DC bus can arrive around 800V when the vehicle is breaking, you do not want condensation around). Using SR motors is opening another challenge. For take max advantage of the technology, you want the motor spinning pretty fast (motor get smaller for same size of rotor and with that design, no problems retaining magnets). That means use high ratio gears. In off road vehicle are often used planetary gears because they are compact and cheap. As soon you rise the input speed, the efficiency of those kind of gears drop because you incur in hydrodynamic loss (for a series of problems that are connected to the level of oil that you need to keep in the gear housing). Probably if you are using an SR motor, you want consider to use an angular stage like first reduction after the motor.

I’m not too sure if I would use a battery like energy storage. Batteries take time for convert from electrical to chemical. Most of the braking will happen in a short time so you will end up burning most of the regenerated energy trough a braking resistor (the DC bus can’t go up to infinite about voltage). If you are driving a dozer that has a very low efficiency (most of the vehicle kinetic energy will be burnt in the tracks etc. and very little will arrive to the SR motor to be regenerate), probably the regeneration is not too important, on other vehicle is maybe more important so look to capacitors or flywheels for storage is probably more appropriate.