difference between conventional and inverter compressor

i would like to ask what are the difference between the conventional and inverter compressor?
i know that inverter compressor can vary its operational speed, but the conventional one cannnot.
however, in addition to their applications and control methonds, how they are different, especially for their structural point of view? are there any devices in the inverter compressor that are absent in the conventional compressor?

furthermore, if i connect the conventional compressor to an inverter and replace the pulse width modulation control by vfd control, then can i acheive the same effect as the one of inverter compressor?

thanks for answering

addition to the installation of an inverter, are there any other components difference?

It´s difficult to get information about this but as I understand it the lubrication might be a problem with a standard compressor.
How this is solved with the VFD-compressor I don´t know, maybe they only speed it up once in a while to ensure lubrication?

It might also be the case that the bearings are not designed for a higher speed than the rated 50-60Hz?

I can only comment on VFDs on air compressors. They don`t have any lubrication issues but they rely on the suction side of the compressor to draw the oil in from the air/oil separator tank. Dry screws have a separate oil pump for the bearings and gearbox. VFD hermetic scrolls don`t have an oil pump (as far as I know) but maybe larger screws do. I can`t see any problems arising with bearing speeds though

As I understand it after reading some datasheets the motor on a "standard" compressor is "CSIR". The ones for VFD control are a 3-phase PM-motor

Fixed speed and variable speed

just control type and driver type not same. becuase the compressor 's motor is not same.

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Originally Posted by ryanzhao

just control type and driver type not same. becuase the compressor 's motor is not same.

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There are several cases where it can be the same motor.

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Originally Posted by cccheng1428

i would like to ask what are the difference between the conventional and inverter compressor?
i know that inverter compressor can vary its operational speed, but the conventional one cannnot.
however, in addition to their applications and control methonds, how they are different, especially for their structural point of view? are there any devices in the inverter compressor that are absent in the conventional compressor?

furthermore, if i connect the conventional compressor to an inverter and replace the pulse width modulation control by vfd control, then can i acheive the same effect as the one of inverter compressor?

thanks for answering

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one of the differences is the low consumtion of energy and the modulation of the gaz flow according to the load.

I assume you are comparing three phase motors with inverter motors as single phase windings ate very different to inverters. Some failing vrv systems and probably others do use the same compressor for fixed speed and inverter

In most parts of the world where the supply voltage to homes and small businesses is 220/240v 50hz single phase. You will be limited to using single phase motors. However if you use an invertor you now have a three phase output but at 240v.

An invertor fed from a 240v supply, will always give a 240v three phase output, not a 415v output, but a three phase 415 volt fed invertor will give a three phase 415 volt output. Therefore a single phase 240v compressor will not run from an invertor, but a three phase 240v compressor will. But it would be interesting to see if three single phase compressors or motors wired in a common star configuration would run from one invertor, if they were all of equal load and all the start windings cut out at the same time.

Food for thought. :cool:

there is no doubt how beneficial are inverter motors.

From my travels down this path, 3 phase refrigeration compressors may be run by VSD and are only limited by minimum speed required for effective lubrication, and the manufacturer will be able to tell you the maximum operating speed for a given situation.

You will generally get a better (wider) RPM range from a semi than a hermetic, particularly where the semi has an oil pump and does not rely on splash lubrication.

Heat pump / AC inverter compressors are quite different from their fixed speed counterparts, as they are normally being driven by a DC inverter, and the motors have different characteristics to a normal 3-phase motor.