Low frequency convertor

[ash2108]

Output of my 3phase 50hz power source is 5-140Amps ,8v-600v , frequency 0.01hz to 6hz , how to control powerfactor at such a low frequency

 

[KlausST]

Hi,

Input power factor? --> use a PFC stage
or output power factor? depends on load. What is your load?

Klaus

 

[FvM]

What do you mean by "control powerfactor"? It's a property of the load, not the voltage source.

 

[ash2108]

Hi,

Input power factor? --> use a PFC stage
or output power factor? depends on load. What is your load?

Klaus

load is inductive

 

[ash2108]

What do you mean by "control powerfactor"? It's a property of the load, not the voltage source.

yes being load inductive ,we need PF near unity , how to attain

 

[D.A.(Tony)Stewart]

Ridley Engineering explains it fairly well.

Ridley Engineering | - [023] Frequency Response Measurement Part I: Wide Band of Frequencies

ridleyengineering.com

Your specs sound like that of a VFD.

 

[KlausST]

load is inductive

on a purely inductive load you have 90° phase shift ... and it can not do something useful (since real power is zero)

Klaus

 

[D.A.(Tony)Stewart]

on a purely inductive load you have 90° phase shift ... and it can not do something useful (since real power is zero)

Klaus

I suspect your assumption is incorrect for what appears to be 3kVA 3 ph source VFD and there is some type of inductive load where force or torque presents the real power but it is desired to get the near unity p.f. applied to the grid.

But required in this question the range of Vac input and maximum Vdc input that this unknown machine design can tolerate in converting to 8V @ 140A (0.01 Hz) for startup and then ramping up voltage with RPM to 600V @ 5A (6 Hz) 60hz??

The general solution is an "active PFC front-end design". where the ACDC boost converter uses a a sine current shape to match the voltage thus a resistive active ACDC boost regulator.

The PFC loop filter for the DC regulator must be much slower than the line frequency e.g. <2% of 50 Hz =< 1Hz to provide low THD 98 % or better and 98% p.f.
Is this a commercial VFD or a custom design you are working with?

If any of my assumptions need correction please explain with your specs.

 

[FvM]

3phase 50hz power source is 5-140Amps ,8v-600v , frequency 0.01hz to 6hz

I read the question so that you are talking about a VFD. Power factor of 50 Hz AC input is not related to load power factor, in so far the question makes no sense.
As for AC input power factor, it depends on the rectifier circuit, either uncontrolled three phase bridge or active front end (PFC). Former has slightly capacitive phase and distortion, latter ideally unity power factor.

 

[KlausST]

I suspect your assumption is incorrect for what appears to be 3kVA 3 ph source VFD and there is some type of inductive load where force or torque presents the real power but it is desired to get the near unity p.f. applied to the grid.

When you talk about torque ... then you probably talk about a motor. And for sure you are correct about a motor as load. Then the load is not PURELY inductive, but also contains an (non_induchtive) real part.

But the OP does not talk about a motor. All information we got is "inductive" .. not complex... no details..

I guess my answer is as correct/incorrect as the information given by the OP.

Klaus

 

[D.A.(Tony)Stewart]

Klaus: I believe you injected the word "purely" into your thought process and response.

FVM: The "Active PFC design" I suggested is for the primary 50Hz ACDC boost circuit with unity p.f.
The p.f. of the load is then irrelevant and the correction is done on the primary side where it matters.
As far as I know EU PSU's > 100 W must have PFC.
So this sounds to me like a DIY design still waiting to reveal all the requirements for the primary ACDC interface.

 

[KlausST]

Klaus: I believe you injected the word "purely" into your thought process and response.

Indeed I did not add anything. The given information is "inductive" and nothing else. I did not interprete the information. I treated it as given.

But isn´t it so that you did add something that has not been said.
I believe you injected the word "partly" into your thought process response. ;-) ... so you made it from an inductive to a complex load.
But now it´s getting hard ... is there only an additional "R", or maybe even an additional "C". It leaves much more room for interpretations.
And much more possible problems regarding compensation and current spikes...

****

Ask me what´s in a bottle: I answer "water" ... how do you expect it to taste? Don´t you expect it to taste neutral, to be "pure" water?
For sure it could be only 90% water ... but then wouldn´t you expect me to answer "beer" (or the according correct term)?

*****

--> I guess it´s on the OP to give exact/detailed informations.
There is a good chance it is a motor. So why does the OP not state so ... and give a link to it´s datasheet. With "motor" we already know it is complex.
But maybe it´s an inductive heater (btw: here the word "heater" tells there needs to be true power ...
Maybe it´s something secret... and he does not want to disclose.

Klaus

 

[D.A.(Tony)Stewart]

I understand your position, but it obfuscates the real question with unnecessary truths. We all like to clarify the "specs", but I suggest you think about what is necessary and redundant or unnecessary noise". This can apply to many including myself in the effort for continuous improvement in our group communication to be mindful of what is needed to make progress in problem-solving.

load is inductive

on a purely inductive load ... was that his question? He is asking for p.f. correction.