Low frequency convertor

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

Hi,

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

Klaus

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

KlausST said:

Hi,

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

Klaus

Click to expand...

load is inductive

FvM said:

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

Click to expand...

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

Ridley Engineering explains it fairly well.


Your specs sound like that of a VFD.

ash2108 said:

load is inductive

Click to expand...

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

Klaus

KlausST said:

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

Klaus

Click to expand...

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.

ash2108 said:

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

Click to expand...

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.

D.A.(Tony)Stewart said:

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.

Click to expand...

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

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.

D.A.(Tony)Stewart said:

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

Click to expand...

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

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.

ash2108 said:

load is inductive

Click to expand...

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

Hi,

In post#2 I asked the OP for more information.
In post#7 I replied to the OP´s given information. And still I stand to this post... and I was finished so far. It´s a conversation between the OP and me.
If the OP is not happy with my answer ... he will post. If the OP wants to give new information .. he will post.

In post#8 But then you did refer to my post ... I don´t see any "problem solving" (as you wrote) in this intrusion. But for sure, if you address me, you should expect me to reply.
If you don´t want me to reply ... then simply don´t quote my post.
Is it wrong to say: you made it a discussion between me and you"? Or is there any evidence that I addressed you?
If you don´t want "unnecessary noise" then simply don´t start it.

D.A.(Tony)Stewart said:

but it obfuscates the real question with unnecessary truths.

Click to expand...

So "your assumed truth" is more true and more worth than mine? And you want me to "adjust" to your truth? So you don´t treat us both equal?

I treaded your assumption with respect and never pushed you to change it.
And I simply want to be treated the same way.
***

ash2108 said:

load is inductive

Click to expand...

D.A.(Tony)Stewart said:

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

Click to expand...

No. It was no question at all. The first part was the OP´s reply on my post#2. ... And then I again replied to this.
It was a converation between the OP and me. Only the OP and me.

***
I can only repeat: It´s the OP´s job to provide clear informations.
And I don´t want to disccuss about assumptions because of unclear informations.
You can have your opinion... and I like to have my opinion.

So I want to politely ask you to clarify application details not with me, but with the OP. I will do it the same way.
I respectfully treat the OP as an adult who can speak for himself. In my opinion he does not need a second person to talk for him.

Klaus

At the risk of being pedantic, let's be honest.
A VFD is never used to drive a pure inductive load.
A VFD is unlikely to be designed to any pf. other than unity, so why ask and as FVM said you never control p.f. of the output load only the input current.
So far at least my assumptions seem valid.

ash2108 said:

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

Click to expand...

ANSWER:

You don't control PF of the load frequency as that is generated by a full wave power generator such as a Class D or E amplifier or Infineon's 3kW bridgeless solution.

You ONLY control the input current at line frequency to unity p.f. using a boost regulator to the TBD specified range of inverter.

Due to lack of OP feedback, I recommend closing this question.