TM-G Thermal-Magnetic Trip Unit
Introduction
The TM-G thermal-magnetic trip unit has low thermal and magnetic pickups. It is designed to protect long conductors and/or distribution systems powered by generators.
There is one configuration of this trip unit: 3P, 3D.
Description
Setting the Thermal Protection
The thermal protection pickup Ir is set by a 4-setting dial.
Turning the thermal protection adjustment dial (A) modifies the trip curve as shown (B).
The following table shows the values of the pickup Ir (in amperes) for thermal protection (values indicated on the dial) with respect to every trip unit rating, relative to the position of the dial Ir.
|
Trip unit rating In (A) |
16 |
25 |
40 |
63 |
|---|---|---|---|---|
|
Pickup Ir (A) |
11 |
18 |
28 |
44 |
|
13 |
20 |
32 |
50 |
|
|
14 |
23 |
36 |
57 |
|
|
16 |
25 |
40 |
63 |
Setting the Magnetic Protection
The magnetic protection pickup Ii cannot be adjusted and equals the value shown below:
|
Trip unit rating In (A) |
16 |
25 |
40 |
63 |
|---|---|---|---|---|
|
Pickup Ii (A) +/- 20% |
64 |
80 |
80 |
125 |
Example of Application
Protection of an incoming feed with the following characteristics:
-
Power supplied by a generator defined by:
-
Generator power 40 kVA - 400 V, giving an operating current of 58 A
-
Subtransient reactance: 30%
-
-
Generator protection. The loads mainly consist of heating and lighting (incandescent bulbs). The neutral is distributed.
The following illustration shows the installation diagram:
Calculations performed on the installation in accordance with the regulations have determined 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 = 57 A |
ComPact NSX100 |
Determination of case size |
|
Distributed neutral |
4P, 3D |
Full neutral and linear loads |
|
Isc = 0.3 kA |
B |
Icu performance can be read from rating plate |
|
Ikmin = 0.25 kA |
TM-G |
Generator protection circuit breaker |
The following table presents the trip unit protections settings:
|
Installation |
Chosen trip unit |
Comments |
|---|---|---|
|
In = 57 A |
TM-G 63, Ir set to 57 A |
Thermal protection Ir setting |
|
Ikmin = 0.25 kA |
Ii =125 A |
Low pickup magnetic protection Ii cannot be adjusted |