CEE Oct-Dec 2002

The site performance of an AC dri ve solely dependent on its sizing - it is here, the buyer has to be careful to see that he is getting the ri ght sized product for his <lpplication and site condition. Most buyers generally indicate the preliminary specifications and then expect the supplier to assume and env isage other key spec ifi ca tions- thi s gene rall y res ults in the supplier assuming parameters to hi s advantage which may not be the factual condition. It is with this desi re, that we have high li ghted below the key parameters which the buyer needs to spec ify and contirm from the suppl ier wh ile evaluating vari ous makes. The fact that almost 70 per cent or fai lures o f power el ectroni c equipment is attributed to thermal failure of components. The AC drives are designed to operate at certai n ambient conditions and they need to be de-rated if operated at higher ambient temperatures. If th e maximum amb i ent tempera ture at your site is 43 °C then the m1n1mum design temperature should be 48 oc for the inve1 er module housed inside the punel. If the voltage at yo ur si te remains at 4 IOV to 435 V during most pa rt of the day, se lect an inverter havi ng a voltage range 400- 440, +/- I 0 pe r cent. Overload, i.e. to deliver more than its capacity for a small duration is alway s des ired to overcome known and unknown loading conditions in the process. Overload duty class II as per I EC- I 46 is I SO pe r cent for 60 seconds. T hus, minimum overl oad of ISO per cen t for 60 seconds is suggested. Di ffcrent manufacturers follow different guide lines to calculate the kW/kVA of thei r powerpack .. Th is is ev i dent fr om the fact th at amperc(current) ratings of id e nti c::~! kW model is different f rom manufacturer to manufacture r. Hence the best parameter of buyer's interest shou ld be purely Current Rating of the Inverter rather than kWorkVA. With penalties now being impo~ed by Electri city Boards for not maintaining the harmonics generation below the prescribed level, more and more eff011s are on towards reduci ng harmoni cs. L ike any other switching device , AC drives constitute one of the culprits generating harmonics. Possibl e so luti ons to red uce harmonics generated by AC drives are: a) Install a DC or AC input reactor. This is a must irrespecti ve of ratings. b) The harmon ics generated by this system wi II be of the order 12n ± 1. Thus, most predominant harmonics l ike s•h, 7'h, 17'h, !9'h .. .., are eliminated on the I I V si de of the transformer. Thus, 12-pulse recti f icat ion co n f ig uration drastic aII y reduces harmoni cs current. Hence for the higher kW ratings a 12-pulse rectification scheme is recommended. When motor to inverter-panel cable distances are long ( in excess of 30m). due to stand ing wave phenomenon. high voltage spikes are generated at motor terminals. General purpose motors are not designed for such voltage spikes and su ffe r premature burn-out/ failu re of th ei r wi nd ing. To safeguard motors aga inst these voltage sp ikes, approp ri ate prot ecti on device needs to be provided at output of the inve1 er, e.g. output reactor, sinusoidal filter. Cuurlesy: Indian Cement Review,Sep.2002 Pp21-23, Fax: 0091-22-2072102 E111Gi/: wadllerapltb l icalion@vsnl.net.in ENERGY EFFICIENCY ANDCONSERVATION Ediloria/ Eve r since th e o il shock o f ! fJ73, there has been a lot of talk 48 on .saving energy. albeit li ttle has been achieved in thi s regard. Unfortunately, the suggestions and recommendations remained o n paper and implementation on these did not take off. Importantly, the Energy ConservatiOn ~ct 2001- a proactive piece of legislation spel ls out the roadmap for the country to mov e up th e energy efficiency ladder. The magnit ude of energy consump tion is v iewed as an i ndica tor of th e st age of competitiveness of an economy. There appears to be a high energy wastage in India as it consumes 50% more energy than USA and four times more than that in Japan to produce one unit o f GOP. In the hi ghly competitive g lobali sed env ironment. count ri es w ith high energy intensi ty ac tu al ly face deceleration in economi c growth clue to high energy input cost. Energy effi ciency projects aim at reducin g ene rgy costs \\ hi lc i rn proving profitab iIi ty <1 nd productivity. To promote energy effi ciency projects, f inancing barriers faced by the cnerg; consuming secto r s have to be removed and innovative funding and financing oplions need to be made available to them by sensi ti sing the financial inst itutions to priori ty lend lor energy eniciency projects . Markets i n energy effic iency ca n be created by effective energy effic iency po li cies through be tt er standa rd f or appl iances and equipment, energy efficiency Iabeii ing, rati on<1l cost– or-ser vice based tari rrs. mandatory energy audi t s, awareness and trai n ing. financial and fiscal incentives. Courtesy: F!CCI Business Digest .lug. /6-3/. 2002, f>-1 Fux: 91-11-332071-1, 3 71150-1 Emoil: ficcira !ficci.com