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Custom Designed DC Filter Chokes
For 50/60 Hz Rectifiers

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Products:

 

Toroid Corporation has developed a new concept for low frequency chokes based on its in-depth knowledge of toroidal design.

Our chokes are smaller in size, have less weight, run quieter, and have smaller losses than ordinary chokes. The low strayfield also permits mounting of our chokes flush to the chassis.

In many rectifier applications, our chokes are used as a better alternative to capacitor filtering. One typical application is ordinary rectifier circuits with high voltage requirements for which capacitors are both bulky and expensive. Another application is reversible DC motor controls where a filter choke reduces the motor losses and improves the motor torque.

 
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Rectifier with choke filtering


A rectifier with choke filtering needs only a small capacitor, or no capacitor at all. An added advantage of choke filtering is that the VA rating of the rectifier transformer is reduced from about 1.5 times the DC power (for capacitor filtered rectifiers) to about 1.1 times the DC power (for choke filtered rectifiers). This reduction in transformer size and cost can be subtracted from the size and cost added by the filter choke.

Our low frequency chokes are also used in AC circuits as balancing transformers for current splitting and current combining, and as ballast reactors.

 
Chart
The following chart shows available core sizes with maximum DC current ratings. To calculate proper size choke, you need to tell us your required No Load DC voltage, DC current (maximum and minimum values) and minimum inductance. You may also want to use the worksheet at the bottom to do your own size calculations.
 
Core
No.		 Size
OD x H		 Weight Lbs. Idc max Amp. Pdc max (W) ý‡L‡Iœ
Ws		 Pcu
W
50 Hz 60 Hz
L-30
L-50
L-80		 2.8"x1.3"
3.2"x1.4"
3.7"x1.4"		 1.0
1.4
1.8		 7.0
6.5
7.7		 60
90
190		 72
110
230		 .094
.14
.31		 4.8
5.5
11.9
L-120
L-225
L-330		 3.7"x1.8"
4.5"x1.6"
5.1"x1.7"		 2.5
4.0
4.9		 7.7
7.0
25.0		 270
420
540		 320
500
650		 .43
.66
.85		 14.1
18.2
17.0
L-500
L-800
L-1200		 5.5"x2.3"
6.3"x2.3"
6.3"x3.2"		 7.4
11.4
16.1		 27.0
25.0
25.0		 920
1,400
2,200		 1,100
1,650
2,600		 1.45
2.20
3.70		 23.5
31.0
38.7

Worksheet
To select the proper choke size:

1. Take the desired DC voltage at no load, and add 2V (FWB) or 1V (DHW).
2. Multiply the resulting DC voltage by your rated DC current to get the DC Power (Pdc).
3. Go to column 5 for 50 Hz rectifiers or go to column 6 for 60 Hz rectifiers (pdc max). Find a choke size that has the same or larger DC Power than calculated above in step 2.
4. Go to column 4 (Idc max). Check that the current listed here is equal to or larger than your rated current. If not, select a choke size that will support your rated DC current.

After you have selected a size for your choke:

5. Calculate the DC voltage drop over the choke by dividing Pcu in the last column (for the size you have selected) by your rated current. (The DC resistance in the choke is Pcu Divided by the square of the rated current.)
6. You can calculate the inductance of the choke as follows:
Divide Ws from column 7 (for the choke size you have selected) by the square of your rated current. Multiply the result by 2, and you have the inductance in Henry.

Note: If Pdc max. from column 5 or 6 for the selected choke is much larger than the DC Power (Pdc) from step 2, both the DC voltage drop (step 5) and the inductance (step 6) can be reduced by using fewer turns of heavier wire. The max. reduction is proportional to the square of (pdc/Pdc max.)
 Vdc (no load) + 2 = ________V

Pdc = ___________W

Pdc max = ________W
Core No. _________

Idc max = __________A
Idc rated = __________A
*If Idc rated > Idc max, then choose new core:
Core No. __________

Vdc choke = _________V
R choke (dc) = __________

L choke = ___________H

Click here to specify a transformer

 

 


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