请问交流变交流的变频器普遍么？

daisy79

如题，就是不经过直流电。直接交流变交流。感觉跟传统的不一样啊。
还有那个变压器是什么原理。副边两个绕组都是角形。

江海直达

A cycloconverter (CCV) or a cycloinverter converts a constant voltage, constant frequency AC waveform to another AC waveform of a lower frequency by synthesizing the output waveform from segments of the AC supply without an intermediate DC link (Dorf 1993, pp. 2241–2243 and Lander 1993, p. 181). There are two main types of CCVs, circulating current type or blocking mode type, most commercial high power products being of the blocking mode type.

江海直达

江海直达 发表于 2016-7-22 15:25
A cycloconverter (CCV) or a cycloinverter converts a constant voltage, constant frequency AC wavefor ...

江海直达

江海直达 发表于 2016-7-22 15:25
A cycloconverter (CCV) or a cycloinverter converts a constant voltage, constant frequency AC wavefor ...

The competitive power rating span of standardized CCVs ranges from few megawatts up to many tens of megawatts. CCVs are used for driving mine hoists, rolling mill main motors, ball mills for ore processing, cement kilns, ship propulsion systems, slip power recovery wound-rotor induction motors (i.e., Scherbius drives) and aircraft 400 Hz power generation. The variable-frequency output of a cycloconverter can be reduced essentially to zero. This means that very large motors can be started on full load at very slow revolutions, and brought gradually up to full speed. This is invaluable with, for example, ball mills, allowing starting with a full load rather than the alternative of having to start the mill with an empty barrel then progressively load it to full capacity. A fully loaded "hard start" for such equipment would essentially be applying full power to a stalled motor. Variable speed and reversing are essential to processes such as hot-rolling steel mills. Previously, SCR-controlled DC motors were used, needing regular brush/commutator servicing and delivering lower efficiency. Cycloconverter-driven synchronous motors need less maintenance and give greater reliability and efficiency. Single-phase bridge CCVs have also been used extensively in electric traction applications to for example produce 25 Hz power in the U.S. and 16 2/3 Hz power in Europe
Whereas phase-controlled converters including CCVs are gradually being replaced by faster PWM self-controlled converters based on IGBT, GTO, IGCT and other switching devices, these older classical converters are still used at the higher end of the power rating range of these applications.

江海直达

江海直达 发表于 2016-7-22 15:28
The competitive power rating span of standardized CCVs ranges from few megawatts up to many tens o ...

江海直达

江海直达 发表于 2016-7-22 15:31

A cycloconverter refers to a frequency changer that can to change AC power from one frequency to AC power at another frequency. This process is known as AC-AC conversion. It is mainly used in electric traction, AC motors having variable speed and induction heating.
A cycloconverter can achieve frequency conversion in one stage and ensures that voltage and the frequencies are controllable. In addition, the need to use commutation circuits is not necessary because it utilizes natural commutation. Power transfer within a cycloconverter occurs in two directions (bidirectional).
A major problem with cycloconverters is that when it is operating at small currents, there are inefficiencies created with firing delay. Furthermore, operations are only smooth at frequencies that are not equal half frequency input values. This is true because a cycloconverter is an AC- AC converter that is phase controlled. Therefore, for it to give the required AC output voltage, it has to do a selection of the voltage input segments by applying line (natural) commutation. This explains why the output frequency is lower than the frequency input.
Harmonics in a cycloconverter are mainly affected by methods of control, overlap effect, the number of pulses in a given cycle, operation mode and mode of conduction.
There are two types of cycloconverters−

• Step Up cycloconverter − These types use natural commutation and give an output at higher frequency than that of the input.
  
• Step Down cycloconverter − This type uses forced commutation and results in an output with a frequency lower than that of the input.
  
  

Cycloconverters are further classified into three categories −

• Single phase to single-phase − This type of cycloconverter has two full wave converters connected back to back. If one converter is operating the other one is disabled, no current passes through it.
  
• Three-phase to single-phase − This cycloconverter operates in four quadrants that is (+V, +I) and (−V, −I) being the rectification modes and (+V, −I) and (−V, +I) being the inversion modes.
  
• Three-phase to three-phase − This type of cycloconverter is majorly used in AC machine systems that are operating on three phase induction and synchronous machines.
  
  

江海直达

普遍使用于矿山，水泥，建筑，船舶主推进，等需要低速运转的设备。
比如球磨机搅拌机船舶推进器。

daisy79

谢谢老师，我学习下。