Digitax DBE1100S, User Manual

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DigitAx User Guide
Issue code: dgxu4
5-14
0.5 1 2 5 10 17
1
2
5
10
20
50
100
Balanced operation 3-phase,
from cold state
Time (s)
x current setting (F)
Balanced operation 2-phase,
from cold state
Balanced operation, 3-phase,
after a long period of set
current flow (hot state)
4
3.5
Figure 5–10 Example tripping curves for the
Telemecanique thermal
overload relays type LR2-Dx3xx
3. Calculate the current setting required for the
thermal overload relay, as follows:
I
I
F
A
SET
R
== == ==
max
.
.
13 1
4
3 275
4. Select a model of thermal overload relay that
can be set at 3.275A (eg. Telemecanique
LR2-D1308).
5.
Calculate the maximum current that could flow
through the resistor (eg. due to the braking
transistor becoming short-circuit), as follows:
I
V
R
A
Rpk
R
== == ==
800
22
36
6.
Calculate the overload factor for this condition,
as follows:
F
I
I
S C
Rpk
SET
/
.
== == ==
36
3 275
11
7.
Use the tripping curves to find the time that the
thermal overload relay will take to trip
(eg. 3.5 seconds approximately)
8.
Check that the braking resistor can tolerate the
overload current for this duration.
5.10 Control Keypad
connections
Model size 3
Use screened cable when connecting to a remotely
mounted Control Keypad. Connect the cable
screen to an external ground terminal which should
be as close to the Control Keypad as possible.
The connecting cable should be shielded data cable
having a maximum length of 100m (330ft). For
lengths of less than 1 metre (3 feet), unscreened
twisted-pair wiring may be used. The Control
Keypad connector is a 9-pin D-type socket.
Model sizes 1 and 2
The Control Keypad cannot be mounted remotely.