Questions about bldc card

[jmx66]

Hi all,

Other queries about my burnt bldc card, nearing completion ...


Power: 1500W Bus voltage = 340 V dc

1st About R31 and R32 resistors

Are they true resistors - if yes , values ? -or something to act like metal strips?

Red box with Q1 . Bottom left side .


2nd Now about inductors L1 - > L3

On the board, a SMD - choke i think - was labelled 681, for 681µF ?

Then search on RS-Site and found components,what is the best choice for the job?

15684C 1,12 A 1500 series p 18/ 152 of Murata-magnetics_mini_catalog.pdf

1468431C 3,1 A 1400 series p 21/152

Others?

If someone could give me advices , would be great.


Thanks a lot.

jm

 

[FvM]

Are they true resistors - if yes , values ? -or something to act like metal strips?

They have a resistance value of 0R - just jumpers.

"681" isn't a clear marking, it can either mean 680 nH (respectively 0.68 µH) or 680 µH. Both values would be reasonable somehow. The value could be better estimated from a photo. Besides nominal power, one should also know the moto current rating.

 

[jmx66]

Hi all,

Thanks a lot for your answer, FvM; as usual, fast and clear.

Soon, i'll take a shot of this SMD.

Thanks.

jm

 

[jmx66]

Hi all,

Joined shot of SMD markings.


Power: 1500 W V bus: 340 V so Rated current about:4,5 A

SMD dia: 10 mm Height: 4 mm


Searching with Google, others inductors manufacturers and prices too...

Like these ?

WUERTH ELEKTRONIK|74462250007|CHOKE, COMMON MODE, 0.7MH, 4.7A | Farnell United Kingdom

**broken link removed**

I'm going to rebuild this card with discrete components not SMD.

Thanks a lot.

jm

 

[FvM]

The shown inductor is operated with a LM2574 buck converter and won't need a higher current rating than 0.5 A. It's 680 µH. An inductor carrying the motor current should have a 4.5 A current rating.

 

[jmx66]

As usual, thanks a lot FvM.

jm

 

[jmx66]

Hi all,

If i want only use an inductor carrying motor current, in order to add less components in the board; is this inductor able to perform the job?

In fact in datasheet, there is 250 V ac and can i say 230 V ac x 1,414 =350 V dc ?

Maybe mistake ......

WUERTH ELEKTRONIK|74462250007|CHOKE, COMMON MODE, 0.7MH, 4.7A | Farnell United Kingdom


Thanks a lot.

jm

 

[FvM]

Two remarks:
- This is a current compensated common mode coke, it can't be used to filter the phase current. The core will saturate at a common mode current far below the specfied current rating.
- It has a 250 V AC rating, so a safe insulation for 350 Vp can be expected.

 

[jmx66]

Thanks a lot .

As i told , maybe a mistake . Yes it is!!!!

jm

 

[jmx66]

Hi all,

After using Google this afternoon, the only things i found were :

-differential mode chokes, but how to choose them?
- toroidal chokes

Right , or like previous post ????

- capacitors X put between phases

I tried also to find with " LM2574 and inductors " , with no really good results....


Any ideas?

Thanks a lot.

jm

 

[FvM]

If you refer to the Wuerth product portfolio, you'll see three choke types
- storage chokes, e.g. 744 13x and 744 15x family in the power magnetics category
- line chokes, e.g. 744 70x x family, category EMC component, filter chokes
- common mode line chokes, e.g the said 744 622 xx family

Storage chokes are intended for high current ripple at switching frequency togther with DC/low frequency currents. They would be used with switched mode converters, e.g. the said LM2574. Line chokes are designed for lower high frequent magnetizsation, but also DC/low frequent currents up to the current rating. The difference between both types is only gradual, e.g. a different core material. But you can basically use a line choke for a switched mode converter, if you accept slightly higher core losses.

Common mode chokes have always two windings and are connected in a way, that the supply current generates no core magnetization. So it can have more windings without saturating the core by the low frequent supply current. But yiu can't use them as storage chokes or to filter a single line.

 

[jmx66]

Again , thanks a lot.

I was really disappointed after " Googling " all the afternoon.

jm