Frequently Asked Questions
MagneX Interrupter and How to Determine Watts Loss
GENERAL QUESTION
Q How do I determine the watts loss for a MagneX Interrupter, since there are several
different sensors and I plan to use them in transformers with different kVA sizes? I also
want to know what the losses would be at different load currents for these transformers.
How can I determine these losses?
1. Based on the kVA and transformer primary voltage, determine full load current of the transformer.
2. Use the same information to determine the MagneX Interrupter sensor size by going to Table 6 in Catalog section
240-34. This table is also shown below.
3. Then go to the charts on the reverse side. Find the corresponding sensor curve and read watts loss on the vertical
scale.
4. For a load current less than 100%, determine the percent load and multiply the full load current by this percentage.
5. Example: 50% load = .50 x full load current.
6. Follow the same procedure as in Step 3 above.
Primary Voltage kV
kVA/kV
2.4
4.16
4.8
6.9
7.2
7.627.97
8.32
12.00
12.4713.2
13.814.4
19.92
10
E06
E06
E03
E03
E03
E03
E03
E01
E01
E01
E01
15
E10
E06
E06
E03
E03
E03
E03
E03
E03
E03
E01
25
E18
E10
E10
E06
E06
E06
E06
E03
E03
E03
E03
37.5
E25
E18
E12
E10
E10
E10
E10
E06
E06
E06
E03
50
E30
E18
E18
E12
E12
E12
E10
E06
E06
E06
E06
75
E50
E30
E25
E18
E18
E18
E18
E10
E10
E10
E06
100
-
E40
E30
E25
E25
E25
E18
E12
E12
E12
E10
167
-
-
E50
E40
E40
E30
E30
E18
E18
E18
E12
Notes:
Recommendations are based on:
• Minimum trip curves, and Maximum trip and clear curves, R240-91-310.
• Deration factor of 0.5% per °C above 25°C.
• Allowable loading greater than 140% for four hours in accordance with ANSI/IEEE Standard C57.91-1961 Guide for
Loading Distribution Transformers, Table 6.
Cooper Power Systems
1045 Hickory Street
Pewaukee, WI 53072
P: 877-CPS-INFO
FAQ-MagneX
October 2007 - New Issue
www.cooperpower.com
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MagneX FAQ
MagneX Interrupter and How to
Determine Watts Loss
MagneX Watts Loss vs. Load Current
30
E50
Watts Loss, W
25
E40
20
E30
15
E25
10
E18
E01 E03 E06
5
E12
E10
0
0
10
20
30
40
50
Primary Load Current, A
MagneX Watts Loss vs. Load Current
E01, E03, E06 and E10 Sensors Only
5
4.5
E01
E06
Watts Loss, W
4
E03
3.5
3
E10
2.5
2
1.5
1
0.5
0
0
1
2
3
4
5
6
7
8
9
10
Primary Load Current, A
Note:
The curves in the above charts were calculated based on the nominal resistance between incoming terminal and the outgoing
terminal of the MagneX Interrupter.
Contact your Cooper Power Systems representative or call 1-877-CPS-INFO to learn more about
the MagneX Interrupter.
Cooper Power Systems
1045 Hickory Street
Pewaukee, WI 53072
P: 877-CPS-INFO
www.cooperpower.com
FAQ-MagneX
October 2007 - New Issue
Printed in USA