1. Mentioning inverters in Japan, most people think of the energy saving devices fitted in air conditioners. These simple, basic devices for use in the home do not, however, fall within the scope of this article, which is instead concerned with full-fledged inverters for industrial use.
   
   
2. Inverters are devices that convert direct current into alternating current. In contrast with a rectifier, which is a converter that converts alternating current to direct current, an inverter is a type of power converter that does the reverse, and it plays a central role in power electronics technology.
   
   
3. General-purpose inverters are defined under 100kVA and mass produced under standard specifications and designed mainly to drive general-purpose three-phase squirrel-cage induction motors with less than capacity of 37kW. One maker defines them as devices less than 110kW or under sold individually and used at low voltages of 200-400V. The Japan Electrical Manufacturers' Association defines a general- purpose inverter as one with a capacity under 75kW (1 h.p.). General-purpose inverters control frequency and voltage, and installing one that matches the motor's rating between the power supply and motor enables speed control (connected at approximately 1:20) to be performed more cheaply and easily than using a conventional, expensive and bulky mechanical nonstep variable speed gear.
   
   
4. Used as variable speed drives to meet industry's energy conservation and rationalization needs, demand for general-purpose inverters has expanded massively since the start of the 1980s due to continuous product development fully incorporating advances in power device and control technology. Demand increased from just a few tens of thousands of units in the early 1980s to that shown below in the 1990s:

   Year	Units	Value
   1991	870,000	¥61.7billion
   1994	1,130,000	¥62.6billion
   1997	1,710,000	¥77.0billion

   In 1999, demand is forecast to reach 1,950,000 units. The reason why there has been relatively little growth in terms of value in comparison with unit demand is because prices have fallen.

   (Source: The Japanese Electrical Manufacturers' Association, "Growing Demand for Inverters 1999".)

5. Expansion of usage is one of the main causes of the growth in demand for general-purpose inverters. They are now used in most types of equipment and machinery, such as (1) civil engineering and construction machinery, (2) food processing machinery, (3) transport machinery, (4) textile manufacturing machinery, (5) chemical machinery, (6) packaging machinery, (7) woodworking machinery, (8) metalworking machine tools, (9) metal processing machinery, (10) fans and pumps, (11) paper manufacturing and printing machinery, (12) healthcare and medical equipment, (13) amusement industry equipment, and (14) environmental and lifestyle-related equipment. Recent examples of new uses include their installation in shampooing equipment in barbershops, and they are also now used in hybrid cars.
   
   
6. Inverters are included among "silicon rectifiers" for statistical purposes, and so there are no accurate data on output and export of inverters alone. However, a considerable proportion (40% at one maker) are exported from Japan to the USA and EU. Within the EU, the commonest destinations are the UK, Germany and Holland. The main destinations of exports to Asia appear to be Taiwan, Singapore, South Korea and Hong Kong. Exports to Japan are practically zero.
   
   
7. Leading Japanese manufacturers advanced to the USA, China and UK but their goods produced there are mostly sold at the places and the reverse import from there into Japan is almost none. At first, main Japanese producers installed the bases for the maintenance here and there but due to increase of local demand and appreciation of the yen, they had to make the plants overseas. There are many cases that overseas plants usually make mass-production products quality of which is stable and they are rather a little bit old type models. As the new products must improve their improper points and make it quality stable, they are mainly produced in Japan. Those manufactures correspond to complaints, requests of improvement form clients.
   
   
8. Japanese makers are unrivalled, and account for almost 45% of world output if production in other countries is included.r@There are a few other inverter makers to be found in the USA, Germany, Switzerland, Taiwan and South Korea, but there are no fully-fledged makers in Asia.
   
   
9. Due to the increasing need in industry to save energy (for example to develop ISO14000-compliant environmental management systems and reduce CO2 emissions to prevent global warming), the spotlight is on inverter technology as a means of conserving energy. As general- purpose inverter technology becomes increasingly advanced and the need for high performance, high value-adding and energy saving technology grows, demand will undoubtedly increase. The market is also likely to grow more as use expands in new fields in the residential sector, such as for healthcare and medical equipment, amusement industry equipment, and environmental and lifestyle-related equipment.
   
   
10. One maker has already developed a non-variable-speed energy- saving model, which serves as one indicator of the possible course of development of inverter technology in the 21st century. Size and costs will also likely be further reduced.
    
    
11. If it is assumed that inverters can be installed in 50% of motors, then as inverters are installed in 15% at present, there remains considerable scope for growth in demand for inverters. In the US, use of inefficient motors incurs a fine of $100 per motor per day , and if laws and ordinances in Japan are made similarly rigorous, then inverter demand will naturally grow. In short, the inverter is a product that is indispensable to conserving energy.

(Cooperation: Yaskawa Electric Corporation and The Japan Electrical Manufacturers' Association.)