Need IPM and Compressor help

[Husky250]

Hi guys,
Im new here and posted this once, but in the wrong place I think. Im currently trying to learn IPM circuits and how they operate a DC Inverter Compressor. I understand the concept of DC voltage supplied to the IPM and three phase supplied to the compressor. I cant nail down sequence of operation from there. How does it work? I would like to be able to troubleshoot the IPM or compressor if I needed to. If anyone knows of any books on the subject please let me know. I would greatly appreciate any help. If it matters Im working on a Sanyo R-410A DC Inverter Series 26,000 BTU

[paul_h]

The IPM is a fast switch, that switches the 3 outputs at different timings, creating three out of sync voltages, ie three phases.
To test if it's doing it's job, you can by an inverter tester, search the forums with the phrase "inverter tester" for more info.
You could also put a multimeter across the IPM outputs and see if all voltages balance out while it's trying to start a compressor, just like you would test three phases to a convention compressor trying to start.
You need a megger to test compressor windings, you need a good multimeter with min/max voltage recording and diode tester.
Optional is a clamp meter that can measure Hz, and an inverter tester from daikin that tests outputs and has pretty flashing lights.

edit: I don't know of any books, most of the info comes from the manufacturers themselves. But there's heap of info on the net, and a lot of good links here that people have posted when they get some info from service manuals.

[Thermatech]

The Japanese are usually very good with detailed service manuals.
The service manual will sometimes give a description with graphs for the basic control stratagy for the compressor speed.
With this information you can usually work out what frequency or speed the compressor should be running at.

Some basic & crude domestic split systems only ramp up as the differential between set temp & room temp increases.These system only have a few compressor speed steps.

The more advanced split systems also look at super heat & subcool data from the indoor unit. The refrigerant flow through the electronic expansion device is adjusted to maintain the preset target value. The compressor also ramps up or down in speed to maintain the targets & have many more speeds.

Some split systems are more like VRF systems as they also have high & low pressure sensors & the compressor ramps up or down to maintain target LP in cooling mode & HP in heating mode & also the system looks at SH & SC and adjusts to maintain targets.The very best systems can adjust compressor speeds in 1% increments.

Some systems also work with fussy logic which means they do not instantly adjust comp speed in responce to changed operating conditions. They are always looking at the operating data trend over a period of time & constantly calculating what to do next based on the trend & so they tend to maintain more stable operating conditions.

For the more advanced systems it is more difficult to understand exactly what speed the compressor should be running at for any specific condition. This is mainly because the manufacturers are reluctant to provide the details of the control stratagy.
This would be like asking an F1 race team to publish the full control statagy for the engine managment system.

[paul_h]

I'll second that.
I was at a VRF unit that would only run at 30% capacity, when the setpoint was 18C and the room temp was 27C. All pipe temps and thermistors were fine. I asked the local representitive why did it only run so low a capacity. He said he didn't know why if there's no fault, they don't even tell him that stuff!
That's why I said there isn't really any books on the subject, you really have to deal with the manufacturers and it's up to them how much info they will share.

[nike123]

http://www.mediafire.com/?md17u5libsf

[Husky250]

Thanks to all of you. Im new to this kind of compressor operation. I see more and more installations with the DC Inverter driven compressors. I look forward to reading the post from you guys and learning all I can. Thanks!

[Husky250]

Here is another dumb question....Why are the terminals marked U-V-W from the IPM board?

[Thermatech]

Cummon Nike123 you have just got to answer this one for us !

[nike123]

Cummon Nike123 you have just got to answer this one for us !
Ok, I just arrived to home.

I think that all answers is in that presentation. If you have any additional question just ask.
I will be happy to answer to your questions.

[nike123]

Cummon Nike123 you have just got to answer this one for us !

Because the DC compressor mimics operation of 3 phase AC compressor it is decided that conections are marked as 3 phase Ac motors.
In normal DC motor we have brushes and collector to transfer current in rotor
This is how it is done:
http://en.wikipedia.org/wiki/Brushed_DC_Electric_Motor#Simple_Two_Pole_DC_Motor

Then, in DC compressor we have brushless DC motor who need rotating magnetic field for his rotation. That is accomplished by introducing 4 pole permanent magnet rotor and IPM circuit who deliver DC current of different voltage and pulse with, and direction, to 2 of 3 poles of stator and shift to the next pair of poles as rotor rotate.


http://farm3.static.flickr.com/2061/2369950509_c8404b9d03_o_d.jpg

This is DC brushless principe:
http://www.comed.se/anhall.html

This is our case:
http://users.tinyworld.co.uk/flecc/4-pole-bldc-motor031102.swf

[Husky250]

Many Thanks for you all taking the time to help me understand the concept of how this all works. In my location the DC Inverter units are popular, but information is not. During my college study there was never any mention of this kind of operation. I have enough information now to study and conduct testing to learn. One question, and you tell me if Im close or wrong. The PCB knows the position of the rotor via BEMF created when the shaft rotates. One slide on the power point presentation shows a total of 6 transistors ( IGBT )( I was told) being switched on/off very fast. Looks like the pulse wave is obtained between U-V, V-W, W-U . The pulse wave is created with two wires, and the third is used for rotor detection via BEMF. This changes quite fast so the rotor detection wire changes quite fast as well. Am I on the right track? Again, I cant Thank you all enough for the information given. I have struggled with this from day one. Its starting to make sense. THANKS!!!!!

[nike123]

One question, and you tell me if Im close or wrong. The PCB knows the position of the rotor via BEMF created when the shaft rotates. One slide on the power point presentation shows a total of 6 transistors ( IGBT )( I was told) being switched on/off very fast. Looks like the pulse wave is obtained between U-V, V-W, W-U . The pulse wave is created with two wires, and the third is used for rotor detection via BEMF. This changes quite fast so the rotor detection wire changes quite fast as well. Am I on the right track?

That is correct for sensorless brushless DC motor.
Here some more explanations.
http://f-cpu.seul.org/~nico/astromech/motor_control/tipntrick_motor.pdf (http://f-cpu.seul.org/%7Enico/astromech/motor_control/tipntrick_motor.pdf)


And this is my first thousand of posts.:D:D

[Husky250]

OK IM on the right track. The systems I deal with run all compressors without a sensor for rotor position. I cant say enough about what Ive learned with this site and you fine folks. Im in the US and these systems are new to us. Very few know anything about them. Trying to get info from the Factory is like pulling teeth. I do understand why they would want to keep some things from going public. At the same time its my idea to know sequence of operation before making a judgement call on whats wrong with the system. Cant ask the enduser to pay for a guess..Thanks to all!