Power Products Technology
Inverter Generators
Pursuing High Quality Electricity and Ease of Use
Sine Wave Inverter Generators that Evolve with Customers' Needs
1. Always Meeting the Needs of Generators
Supplying high quality electricity for various situations, wherever it is needed.
In 1965, Honda released its first commercially available portable generator, the E300.
A large proportion of Honda’s portable generators are powered by gasoline engines. Kinetic energy is generated by the gasoline-powered engine and is then converted into electrical energy, and by housing this process within a compact package, heat and sound are inevitably generated. Honda continues to develop various technologies, striving not only to reduce generator heat and sound, but also to supply stable, low-fluctuation, high quality electricity.
Strong Enough for Professional Use, Easy Enough for Household Use
Honda’s first portable generator was initially popular for outdoor leisure use, but was soon supported as a generator for industrial use at venues such as construction sites, leading to the demand of higher-powered - and larger - generators. On the other hand, as the infrastructure for household electricity improved and electrical appliances boomed in scope and variety, the use of generators went beyond industrial applications, and became more common in daily life, such as back-up power supplies for household appliances and communication devices in case of mains outages. To power these appliances in case of outages, generators gained a new use, with new requirements: In addition to generating high quality electricity to power electronic appliances, a compact and lightweight form with low-noise, and high fuel efficiency became new requirements for generators.
First to Integrate Inverter Technology
In order to meet these needs Honda continues to develop various technologies, one result being the “Sine-wave inverter” control system, which generates electricity with smooth sine-wave characteristics. Honda improved this control technology in stages, to the point where stable electricity of a constant frequency could be generated regardless of engine speed. In 1998, Honda developed the Microprocessor-controlled Sine Wave Inverter, allowing electricity with a waveform clean enough to power ordinary electric appliances, to be supplied according to the load.
Honda continues to pursue the ideal safe-and-secure generator, tackling every issue that arises while meeting changing requirements with the times.
Inverter: Electrical device that converts direct current into alternating current with stable frequency and voltage
2. The Road to the High Quality Electricity-generating “Sine-wave Inverter”
Because portable generators are generally compact with simple mechanisms, voltage output and frequency is influenced by the engine’s performance, and load through generating electricity. Most electrical appliances, however, are designed to work with accurate, low-fluctuation household electricity supplied from a giant power station. With early model generators, problems such as fluctuating lights and non-operating equipment were common. In order to find a solution, Honda pursued the development of inverter technology, striving to evolve the quality of electricity supplied from its portable generators, and albeit in stages, succeeded.
The Stable-frequency EX300
The first generator to be equipped with an inverter circuit was Honda’s EX300, released in 1987. In order to stabilize frequency and improve generation efficiency, the EX300 employed a “3-phase multi-pole high-speed generation system,” which spun a rotor at high speeds to generate a 3-phase alternating current. Through technologies that enabled electricity generation by increasing generating efficiency, creating a direct current through a rectifier circuit, and maintaining a stable frequency alternating current through an inverter circuit, this system made generators more efficient and easy of use. It could not, however, be used for all appliances, as the waveform it generated was a rectangular wave.
The Sine-wave Generating EX500
The EX500, released in 1996, realized sine-wave generation equivalent to mains power, through the use of purpose-built ICs (Integrated Circuits). At the time, microprocessor technology was applied only to expensive devices such as personal computers. Inverter controllers involved numerous digital processes handled by electronic circuits comsisting of many ICs. This configuration was too complex, so Honda developed an integrated custom IC to control its inverters.
The sine-wave generating system not only solved the problem where some home appliances could not be used due to fluctuating waveforms, but in response to user demand, realized “parallel operation” which automatically synchronizes two EX500s, allowing transportation of two small generators - rather than one large generator. As the EX500’s electricity generation was not dependent on engine speed, it could be operated at higher revs to fully utilize the engine’s performance, requiring an engine only half the size of conventional generators. The EX500 was a large step towards small, lightweight and highly fuel-efficient generators, but considering how users of generators had diversified, Honda realized that to make its products more appealing, work was still required, such as even smaller and lighter generators with cleaner waveforms.
The World’s First Microprocessor-controlled Sine-wave Inverter System
At around the beginning of the 21st century computer technology rapidly developed, enabling Honda to equip portable generators with microprocessors. In 1998, Honda released the EU9i / EU24i / EU28is with CPU data processing control that could minutely cater for attached electrical appliances. The sine-wave inverter system realized such high-quality electricity output that it could power personal computers and other delicate electrical appliances. “Eco-throttle,” functionality that controlled the engine speed according to the usage situation, was also realized through microprocessor control, making the EU9i an even more evolved, easy-to-use and personal generator. Stable frequency output, Sine-waves equalling mains power, and usability such as a compact and lightweight package were all factors in the foundations of Honda’s inverter generators being born.
Rotor: Moving component in the generator that generates electricity through its rotation
3-phase alternating current: Three flows of alternating electric current separated by 120° each
“Eco-throttle” - High Fuel Efficiency, Low Noise
The advent of the inverter system gave birth to “Eco-throttle,” a technology that automatically controls the generator’s engine speed according to the electrical load, enabling the output of as much power as required on demand.
Under low-load conditions, operation time is longer, fuel consumption is lower, and noise is lower. With conventional portable generators, output was dependent on engine speed, which meant either high-output or low fuel consumption/noise had to be sacrificed. “Eco-throttle,” Honda’s highly-developed inverter control technology, realizes high-output and low consumption/noise.
3. Pursuing "Compact" and “Lightweight" that Match Ease of Use
Portable generators require excellent electric performance, but being compact, lightweight, low-noise and highly fuel efficient are also vital attributes. The EU series released in 1998 aimed to realize all of these requirements with its class-first microprocessor-controlled sine-wave inverter system, and endeavored to halve the weight compared to conventional generators, with a completely new design. Through developing numerous technologies it achieved its goals, and the 13kg EU9i became the standard for Honda’s inverter generators.
Designing the High-speed Multi-pole Outer Rotor Alternator
A high frequency 3-phase alternating current is generated by the electric generator, which through a rectifier circuit and inverter is output as a sine-wave. With the EU series, Honda developed a dedicated high-speed multi-pole alternator. By designing the alternator to act also as the flywheel, the generator’s weight was reduced by one-third compared to conventional generators.
Microprocessor-controlled Inverter Unit
The inverter unit rectifies high frequency alternating current from the alternator and outputs low-distortion sine-wave alternating current, and also controls the engine’s load-linked rotation-controlling electronic governor. By equipping its generators with microprocessors allowing accurate and high-speed control, Honda’s generators are more compact, appealing to a wider range of customer.
High Efficiency Cooling
The inverter, alternator, engine and muffler are positioned in ascending order of heat dissipation and temperature to create an efficient cooling structure. This design enabled the engine and alternator to share a cooling fan, reducing unit size and weight.
Double-soundproofing Structure
The double-soundproofing structure, comprising of a soundproof box encasing the engine, and soundproof body, realize ultra low-noise operation.
In addition, durable high performance resin, replacing conventional pressed-steel for components such as the outer cover, contribute to weight reduction as well.
The 21st Century Standard
The technological advancements at around the turn of the century, including the EU series, realized 25-30% better fuel efficiency, and were significantly lighter, smaller and quieter than conventional generators. The EU series, developed with the aim of becoming the “21st Century Generator Standard,” are now available in various models to meet the requirements of a wide range of customers.
Honda will continue to built upon the knowhow gained through listening to its customers, to develop even better generators that meet the changing requirements of the times.
Alternator: A generator that produces an alternating current
Evolving to Make Generators Even More Commonplace
Electricity is used in more and more situations in everyday life and work, and the use of portable generators, which were limited mainly to industrial use such as construction sites, are now used to power everyday life and leisure, back up lighting and televisions as an emergency power source, and recharge information devices such as smartphones.
Compared with large-scale generators, portable generators must evolve to meet the use (such as the occasion, environment and connected electric appliances) by the customer. Clean waveforms are vital, but fundamental technologies also require perfection to produce compact, lightweight generators with high fuel efficiency and low noise.
For example, large generators used as backup power in case of mains outages commonly supply power all night into the morning without refueling. Honda equips generators for these kinds of use with fuel-injected engines, improving fuel efficiency and long term storage and maintenance characteristics, and by increasing the fuel tank capacity, realize a longer operating time.
Honda also offers generator models powered by easily purchased, used and stored home-use canisters. By pursuing not only the selection of fuel, but improvements in storage and operating characteristics, Honda’s engine-powered generators are even easier to use in everyday life.
Honda is also leveraging its generator technologies to develop electricity supplies and chargers to connect electricity between automobiles such as EVs (Electric Vehicles) and FCVs (Fuel Cell Vehicles) and homes and schools.
With the rising awareness of environmental concerns, noise and exhaust emission regulations in each country are becoming even more strict, and the generator market as a whole needs to provide generators powered by not only gasoline, but alternative fuels such as gas.
Honda’s generator technologies will continue to evolve to meet its customers’ needs and fields of usage, and changes in society.