None of the overhead hoist and crane manufacturers, service and sales companies, out of the more than 1,500 we deal with directly, are using other than asynchronous motors. When we discuss the 90% efficiency achievable via the use of variable frequency drives (VFD), it's not optimistic, it's factual. Is it always the case? Maybe not, but in reality these efficiency figures have reached 94%.

As regards the continuing usage of asynchronous motors in Overhead Hoist and Crane applications, if there is a manufacturer using anything other than that, with the exception of consequential pole motors, I am in touch with many and as yet that roster remains, to the most current information I have available, empty.
In summary, when using a VFD there are many benefits and cost saving possibilities for pumping applications in the irrigation sector. It is important to look at a VFD application for a motor in conjunction with the curve of the pump. The hydraulics of the system need to be understood and best is to plot the curve onto a simulation program which can show how the varying speed influences the characteristics of the pump. This coupled with the change in kilowatts power consumed at the different duty points will allow the customer to make an informed decision.
Most DC brush motors are used in the VFD system for the past treadmill to save cost. However, its weaknesses are the high failure ratio of carbon-brush and commutator device, high maintenance cost and inefficient low-speed torque. Thus, most manufactures adopt the AC motor with the variable frequency drive to improve the weaknesses of the DC motor.
Global warming is one of the greatest feared disasters in human history, and with its deteriorating effects, it should cause concern to all human beings. Combating global warming by reducing CO2 emission and saving energy are things we can do to help reduce the effects of global warming. Taiwan is located in the sub-tropical zone, therefore, every building is equipped with air-conditioning systems. If we adopt reasonable and intelligent technology, plus the best modern design, we can conserve energy, as well as maintain a comfortable working and living space.
Application of Gozuk VFD in wire and cable industry, have solved the electric control problem of power pay-off wire rack and take-up wheel in the industry. The line connection is simple. The VFD has PID and closed-loop control function itself, instead of the A/D, D/A modules and PLC programmed. Any common electric maintainer can operate it. Gozuk VFD should be the first choice of reform for old pay-off wire rack in wire and cable industry.
1) The drive points of each individual shall be able to start and stop separately and shall be adjustable for their speeds;
2) The complete machine shall be sync speed increasing and decreasing;
3) Speed regulation of one individual can result in a sync speed regulation at this individual and its subsequent individuals;
4) The speed shall be automatically recovered as original operating speed after paper tensioning;
5) The maximum design speed shall be adjustable according to production requirements;
6) The system shall be with emergency stop function.
Currently, most of the oil pump, water pump and air compressor at a constant speed motor drive state, as will account for an absolute majority of the non-governor speed motor into operation, its power consumption varies with the load size, you can save a lot of energy, will produce significant energy-saving effect. Modern power electronics technology, the development of AC variable speed AC Motor Variable Speed huge leap in the frequency range, dynamic response and accuracy requirements, and use effects.
For the spinning frame, peach bottom caused by the use of the variable frequency drive removed the forming mechanism of forming cam pauses, a peach top of the impact of the phenomenon. Good shape of the yarn. In order to under a process of high-speed unwinding. While taking advantage the VVVF control the main motor thirty-nine speed to control the number of revolutions of the spindle, spun medium and small yarn speed changes to reduce yarn breakage rate.
The application of the medium voltage variable frequency drive in the large-sized asynchronous motor is just at the initial stage in China, which, however, has been pretty popular in the developed countries. As the development of the electronic components, types of the medium voltage VFD become very diverse. By the topological structure, the medium voltage VFD can be classified as IGBT module serial-connection type, tri-level type and multiple power unit serial-connection type with voltage superposition.
However, variable frequency drives can create undesirable harmonics. For example, certain harmonics created by the operation of the motor cause problems such as voltage distortion, zero-crossing noise, overheating of transformers, nuisance tripping of circuit breakers, and over-stressing of power factor correction capacitors. Additional losses arise due to huge impact current at start and heavy mechanical wear to the pumps.
The so-called Variable Frequency Drive (VFD) parallel connection technology indicates that two or more sets of small power VFDs are connected in parallel to drive a high power motor. However, since it is inverting frequency output, several problems as follows need be solved firstly.
It is a significant step in China energy saving campaign to apply the frequency conversion technology into the central air-conditioning system. Statistics show that at least 70% of China's central air-conditioning systems haven't had any energy saving function to date, which indicates a huge market for the VFD manufacturers.
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