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Overloaod Protection circuit doubts

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thannara123

thannara123

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Going from some related forum threads , I am asking the doubts follows

Please look the circuits this is the part of my inverter circuits at which AC current mesuare
Here when , overload event occurs, the oscillations starts , i.e the bulb starts blinking very fast. how to remove these oscilations?


test.jpeg

Is this circuit is correct or what is the problem ?

:bang:
 

Can you show what the current signal looks like under these overload conditions?
 

Can you tell us what the load is doing? Is it a motor? What is the light bulb you speak of? The circuit looks ok.
 

E-design said:
Can you show what the current signal looks like under these overload conditions?
Click to expand...

sir unfortunately I haven't a oscilloscope.

- - - Updated - - -

PowerSupplyGuy said:
Can you tell us what the load is doing? Is it a motor? What is the light bulb you speak of? The circuit looks ok.
Click to expand...
At normal load like light smps based loads .

But at transient higher load it will oscillates .

Can i put a capacitor accross the output of the op amp with time Constant [ only with one or two cycle ]
 
Last edited:

Hi,

Your picture only shows a current measurement circuit..but it doesn't show how your load is controlled. There needs to be a power stage.

I assume what you see is a regulation loop stability problem.
* your circuit measures current
* on overcurrent ...your load is shut down
* current is reduced
* your circuit measures current
* there is no overload situation anymore ... your load is powered up again
* current increases
--> start from above

Klaus
 
KlausST said:
Hi,

Your picture only shows a current measurement circuit..but it doesn't show how your load is controlled. There needs to be a power stage.

I assume what you see is a regulation loop stability problem.
* your circuit measures current
* on overcurrent ...your load is shut down
* current is reduced
* your circuit measures current
* there is no overload situation anymore ... your load is powered up again
* current increases
--> start from above

Klaus
Click to expand...

Yes , But How to desgin a situation where need "No overload upto load 300% " for transient or 50 milli second or a just short period .

Can i connect A cappacitor at output of the Opamp .
And can i charge a capacitor till the 300% .
when it exceeds the level 300% the capacitor needs to be discharge at the time shutdown will taken .
 

Hi,

You still give no information about your load driving circuit.
Therefore I need to gues (I don't like this).

I assume that the current measurement signal goes to an ADC and then the digital signal are processed with a microcontroller...
If so, then write some lines of code with your desired function.

With software you are more flexible.
A capacitor with an R gives a delay...for sure it may prevent the "switch ON again" but it also increases the time to detect the overcurrent situation...this usually is not wanted with overcurrent protection features.

Klaus
 

KlausST said:
Hi,

You still give no information about your load driving circuit.
Therefore I need to gues (I don't like this).

I assume that the current measurement signal goes to an ADC and then the digital signal are processed with a microcontroller...
If so, then write some lines of code with your desired function.

With software you are more flexible.
A capacitor with an R gives a delay...for sure it may prevent the "switch ON again" but it also increases the time to detect the overcurrent situation...this usually is not wanted with overcurrent protection features.

Klaus
Click to expand...

I dont have code Because I am purchasing the ready made inverter boards from market .
I have a purchased Hex code , But i am purchasing the ready made board .

Sir any good analog circuit section for correcting this problem

Obviously i know it is the inverter section problem .

Some other inverter with low powered in the market [with respect to mine inverter] is simply working on the above said loads .
 

You seem to want a few layers of specific behaviors
(the various timeouts and overcurrent-ranges) and
you should expect to have to design these, beyond
the simple sense circuit.

This probably entails multiple comparisons, each
applied to a summing logic after passing through
appropriate timeouts. Then the question becomes,
what should the inverter do about it? Latched
shutdown is one common approach, requires user
intervention to restart (safety, good, but bad for
an unattended self-righting operation). The other
is real time, self-releasing, and prone to "motorboating"
as you see.

You can look at power management IC design support
materials and see what industry does, and which of it
seems best for your application.
 
dick_freebird said:
You seem to want a few layers of specific behaviors
(the various timeouts and overcurrent-ranges) and
you should expect to have to design these, beyond
the simple sense circuit.

This probably entails multiple comparisons, each
applied to a summing logic after passing through
appropriate timeouts. Then the question becomes,
what should the inverter do about it? Latched
shutdown is one common approach, requires user
intervention to restart (safety, good, but bad for
an unattended self-righting operation). The other
is real time, self-releasing, and prone to "motorboating"
as you see.

You can look at power management IC design support
materials and see what industry does, and which of it
seems best for your application.
Click to expand...

sir ,I didnt get you as well anyway

I am trying to make it for a specific requirement.

This specific inverter do as " which will not shutdown up to 300% of its capacity only for a 10 millisecond".

I searched too much i didnt get the solution
 

buffer.png
this one. pls let me know if this doesn't work
 

Hi,

You simply don't give enough information to get good answers.
You see there is a lot of confusion.

Post a picture of the whole regulation loop.
Give values. Give charts where we can see the desired function.

Klaus
 
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