MA Magnetic Trip Unit
Introduction
The MA trip unit has a high magnetic pickup. It is designed to provide motor-feeders with short-circuit protection.
The MA trip unit can be used to create a type 1 or type 2 coordination motor-feeder.
Description
Setting the Magnetic Protection
The magnetic protection pickup Ii is set by:
-
A 9-setting dial for 2.5 A to 50 A ratings
-
A 6-setting dial for 100 A to 220 A ratings
The following table shows the values of the pickup Ii (in amperes) for magnetic protection (values indicated on the dial) with respect to every trip unit rating, relative to the position of the dial Ii:
|
Trip unit rating In (A) |
2.5 |
6.3 |
12.5 |
25 |
50 |
100 |
150 |
220 |
|---|---|---|---|---|---|---|---|---|
|
Pickup Ii (A) +/- 20% |
15 |
38 |
75 |
150 |
300 |
– |
– |
– |
|
18 |
44 |
88 |
175 |
350 |
– |
– |
– |
|
|
20 |
50 |
100 |
200 |
400 |
– |
– |
– |
|
|
23 |
57 |
113 |
225 |
450 |
900 |
1350 |
1980 |
|
|
25 |
63 |
125 |
250 |
500 |
1000 |
1500 |
2200 |
|
|
28 |
69 |
138 |
275 |
550 |
1100 |
1650 |
2420 |
|
|
30 |
76 |
150 |
300 |
600 |
1200 |
1800 |
2640 |
|
|
33 |
82 |
163 |
325 |
650 |
1300 |
1950 |
2860 |
|
|
35 |
88 |
175 |
350 |
700 |
1400 |
2100 |
3080 |
Example of Application
Protection of a motor-feeder with the following characteristics:
-
Power supplied by a 1,250 kVA transformer - 400 V, 4%
-
Protection of a motor application defined by:
-
3-component motor-feeder (circuit breaker, thermal relay, contactor)
-
Direct-on-line starting
-
Motor power 110 kW, that is, In = 196 A
-
Type 2 coordination
-
The following illustration shows the installation diagram:
1022Calculations performed on the installation in accordance with the regulations can be used to determine the characteristics of the appropriate ComPact NSX circuit breaker to install (calculations performed using the Ecostruxure Power Design – Ecodial software).
The following table presents the circuit breaker selection:
|
Installation |
Chosen ComPact NSX |
Comments |
|---|---|---|
|
In = 196 A |
ComPact NSX250 MA 220 |
Determination of case size |
|
Isc = 28.5 kA |
F |
Icu performance can be read from rating plate |
|
Ikmin = 14.8 kA |
– |
– |
The following table shows the trip unit protection settings:
|
Installation |
Chosen trip unit |
Comments |
|---|---|---|
|
Ikmin = 14.8 kA Transient current = 14 In, that is, 2,800 A |
Ii = 2,860 A |
The Isd protection setting is compatible with:
|