Can you explain exactly what is the purpose of this proje

To study the behavior (and efficiency) of this gate driver in case it is connected to a motor phase

 

Hi,
Check the specified load current, it is only a Gate driver.
E

 

Hi,
Check the specified load current, it is only a Gate driver.
E

I don't have much experience with power electronics and I'm a bit confused by this step, can you elaborate?

Thank you for your patience

 

Hi,
Do you have the datasheet for the EPC, if yes, check the specified device limits.
If you exceed the limits of the device in a real application it would be damaged, LTS simulations will not show any problem.

Redo your simulation to stay within the device limitations, as per the d/s

E

BTW: is this a College assignment project?

 

hi,
This is d/s clip.
Can you explain exactly what is the purpose of this project?
Note the device specification.

E
View attachment 337967

Yes, I could just rely on the datasheet ... but I also need to simulate on spice this and other drivers at different frequencies and loads. So I'm interested in properly set up a simulation (the .asc file I sent you) at least for one device (EPC2152)

 

Hi,
Do you have the datasheet for the EPC, if yes, check the specified device limits.
If you exceed the limits of the device in a real application it would be damaged, LTS simulations will not show any problem.

Redo your simulation to stay within the device limitations, as per the d/s

E

BTW: is this a College assignment project?

Output is 48V and I want 10A (for example) at the output I could simply put a 4.8 ohm resistor.
Needing also the inductance to simulate the motor, however, things get complicated.

I should then size the impedance (R+jwL) such that I have Iload<15A .. correct?

 

If you add inductance that gets complex because now you are adding reactive power.

 

Redo your simulation to stay within the device limitations, as per the d/s

Because what is not clear to me is how to fit within the limits of the device.

I'm thinking for example to size the load such that for that voltage (48V) it draws a certain current less than the limit on the datasheet. Right?
But the load is not a variable that I can size, it is a constant because it represents the motor I am using.
So I'm not sure how to proceed
@MrChips

 

Don’t add inductance just yet. First solve the discrepancy between LTSpice and Excel.

If you integrate over a very large number of cycles, the error introduced by a partial cycle is minimized. You don’t need to know the number of cycles. Simply divide by the total number of sampled points.

 

Don’t add inductance just yet. First solve the discrepancy between LTSpice and Excel.

If you integrate over a very large number of cycles, the error introduced by a partial cycle is minimized. You don’t need to know the number of cycles. Simply divide by the total number of sampled points.

@MrChips @ericgibbs
I updated the RMS formula on LTSpice and simulated with frequency 10kHz.

LTSpice result: (plotted input power + error log)

Pin_rms_ltspice = 454W

Excel result: (exported input power and calculated RMS)

Pin_rms_excel = 326W

 

hi k89,
Looking over your spreadsheet equations, could you please explain your logic on how you arrived at these equations, step by step, please, they look a little odd to me.

LTS indicates Vin =48v and Irms = 9.46629A.

E

 

hi k89,
Looking over your spreadsheet equations, could you please explain your logic on how you arrived at these equations, step by step, please, they look a little odd to me.

LTS indicates Vin =48v and Irms = 9.46629A.

E

I followed the formula:

First square all the value
Second average calculation (i.e., their sum/how many are)
Third square root

Or you can use =SQRT( SUMSQ(D3 : D25) / COUNT(D3 : D25) )
I obtain the same result

 

hi k89,
Why are you taking the RMS value of a product, already derived using the RMS value? ie: 48V * 9.46629Arms. =454W

By doing so you get this incorrect lower value, eg; 454W * 0.7071 = 321W

E
BTW: is this a College assignment project?

 

hi k89,
Why are you taking the RMS value of a product, already derived using the RMS value? ie: 48V * 9.46629Arms. =454W

By doing so you get this incorrect lower value, eg; 454W * 0.7071 = 321W

E
BTW: is this a assignment project?

No, it is not a college assignment project.

You are right, in the Excel I was wrong in taking RMS value of a product.
So I decided now to calculate the RMS of the output current only (out of curiosity)
If the formula I used in the Excel is correct, why is I_rms different from I_rms on LTSpice?


I'm sure I must have made a stupid mistake, but I can't find it :/

 

hi k.
Using your last posted asc file, this is what I see in LTS, note the edit of the .tran to skip past the initialising period.

Recalc your excel and post

E

 

hi k.
Using your last posted asc file, this is what I see in LTS, note the edit of the .tran to skip past the initialising period.

Recalc your excel and post

E
View attachment 338020

hi k.
Using your last posted asc file, this is what I see in LTS, note the edit of the .tran to skip past the initialising period.

Recalc your excel and post

E
View attachment 338020

I will do the calculations with Excel, but I just downloaded exactly your file and I don't understand why V(sw)*I(R2) values are different:


As for the individual values of V(sw) and I(R2) ... they coincide with yours:



I will attach the excel to you shortly

 

hi k.
Using your last posted asc file, this is what I see in LTS, note the edit of the .tran to skip past the initialising period.

Recalc your excel and post

E
View attachment 338020

I exported the value of current on load R2, then calculated RMS with excel:

It is different from the one in your screenshot found by LTSpice.
I forgot to change the notation from R1 R2 on Excel but it does the same.

I attach the excel in case you want to look at it

 

hi k,
If you are using the LTS plot, pop up label values of V=45.43V * I=9.46A, they give a product of ~430Watts.
Or V^2/4.7R == ( 45.43V ^2)/ 4.7 = 439W

Eff= 430/454 =~ 94.7%

You seem to making the same error as you did on the input Power/Wattage,IE: the values are already in RMS values.

 

hi k,
If you are using the LTS plot, pop up label values of V=45.43V * I=9.46A, they give a product of ~430Watts.
Or V^2/4.7R == ( 45.43V ^2)/ 4.7 = 439W

Eff= 430/454 =~ 94.7%

You seem to making the same error as you did on the input Power/Wattage,IE: the values are already in RMS values.

View attachment 338072

Thank you for the clarification, now it's more clear. I will do more testing.

I don't know if I should open another thread or if I can continue here, I would like to take up the discussion we had started in post #44.

That is, that by adding an inductance to the resistive load, the power increases disproportionately (hundreds of A or even thousands) because of the reactive component.
By the way, the power provided by the power supply (48V dc bus) on LTSpice is also huge because of the infinite current that can be delivered in simulation.

But then how do I truthfully simulate the efficiency of the driver in the case of inductive load like mine?
Is there some kind of clamping that can be done by setting truthful limits?
Are the formulas I used enough? (I attach file below)
..I don't know if I can trust simulated data/plots when there are such unrealistic numbers

I simulated up to 10ms to wait for the end of any intial transients and I start to save data from 8ms to avoid long simulation wait times.
By varying the duty cycle, the situation remains the same

 

hi k,
Your Inductive load currents are exceeding the d/s rated values

I would suggest as a comparison test that you configure your LTS asc circuit to match the example given in the d/s.
Post when ready and we can compare.

This test circuit has an inductive load, also note the Vboot lower value capacitor.
Also use a PWM frequency as shown in the d/s.

E