Reasons for the competition between hydraulic transmission and electric transmission

Hydraulic transmission has been competing with electric transmission. There are several reasons for this.

1) For fixed equipment, electrical energy can generally be directly obtained, and the use of hydraulic energy, but also need a conversion. However, for mobile devices, because most of the current power is still from the internal combustion engine, regardless of whether the actuator uses electrical energy or hydraulic energy, it needs to be converted. Therefore, from the perspective of transmission economy and energy saving, electric drive has not shown obvious advantages.

Therefore, since the end of the 20th century, the application of hydraulic technology has been increasingly tilted towards mobile equipment. According to 2008 statistics, the ratio of mobile hydraulic to fixed hydraulic is 2:1 in Europe and has reached 3:1 in the world.

Fuel cells, which convert the chemical energy of a fuel (hydrogen or natural gas) directly into electricity, are the most likely alternative to internal combustion engines. Toyota already plans to launch a car using fuel cells in the United States in 2015. The European Union is planning to build micro-power stations using fuel cells.   Since the conversion is silent,   it has been used in submarines to   generate   electrical energy. However, so far,   the power density of fuel cells   is still very low, the energy efficiency is not high, and the generation of electricity at the same time, but also produce a lot of heat.

2) There is no danger of hydraulic oil leakage polluting the environment using electric drive. This point, in today's concern about environmental protection, more and more people pay attention to. Some European customers told the author that in their country, in many cases, the compensation penalty cost of a hydraulic system leak will exceed the purchase price of the entire hydraulic system.

3) The noise of the electric drive is also much lower than the noise of the hydraulic pump, which is also very important in some applications.

4) The high power density of hydraulic transmission is particularly valuable for mobile equipment. Despite the emergence of high-speed electric motors, their power density has approached or caught up with hydraulic motors, but in terms
of linear motion, electricity is still not as good as hydraulic. The emergence of superconductor materials greatly improves the current intensity, thereby reducing the volume and mass of electromagnetic actuators and further increasing the power density. However, the so-called high-temperature superconductors that can be found so far,   the operating   temperature is below -130 ° C, which is not practical for construction machinery, and is still only a good wish.

Therefore, if one day fuel cell and room temperature superconductor technology or other new technologies can enter the practical stage and be applied to mobile devices, then hydraulic technology may be replaced in mobile devices.

On the question of technological replacement, the history of locomotive traction can provide us with a good reference. The first locomotive to be used was the steam locomotive (1825), followed by the electric locomotive (about 1840), and the internal combustion engine appeared 70 or 80 years later (about 1920). Today, steam locomotives are largely out of use, and internal combustion locomotives have been used alongside electric locomotives for nearly a century. Although electric power is now common in high-speed trains, diesel locomotives are still used in large numbers.Therefore,   a technology like hydraulics, which has been developed for hundreds of years, developed by hundreds of thousands of people, and used by millions or tens of millions of people, will be replaced by a process that will last at least 10 to 20 years. In these 10 to 20 years, the hydraulic technology itself will appear how many innovations! Therefore, there may be quite a long period of time, it will be electrohydraulic symbiosis, complementary. So, hydraulic technology still has a future.