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Digitax ST User Guide

Issue Number: 5

PVC insulated cable should be used.

Installation class (ref: IEC60364-5-52:2001)

B1 - Separate cables in conduit.
B2 - Multicore cable in conduit
C - Multicore cable in free air.

Cable sizes are from IEC60364-5-52:2001 table A.52.C with correction
factor for 40 °C ambient of 0.87 (from table A52.14) for cable installation
method B2 (multicore cable in conduit).
Cable size may be reduced if a different installation method is used, or if
the ambient temperature is lower.
The recommended cable sizes above are only a guide. The mounting
and grouping of cables affects their current-carrying capacity, in some
cases smaller cables may be acceptable but in other cases a larger
cable is required to avoid excessive temperature or voltage drop. Refer
to local wiring regulations for the correct size of cables.

The recommended output cable sizes assume that the motor maximum
current matches that of the drive. Where a motor of reduced rating is
used the cable rating may be chosen to match that of the motor. To
ensure that the motor and cable are protected against overload, the
drive must be programmed with the correct motor rated current.

UL listing is dependent on the use of the correct type of UL-listed fuse,
and applies when symmetrical short-circuit current does not exceed 100
kA. See Chapter 15

UL listing information

on page 204 for sizing

information.

An MCB (miniature circuit breaker) may be used in place of fuses under
the following conditions:
•

The fault-clearing capacity must be sufficient for the installation

•

The I

T rating of the MCB must be less than or equal to that of the fuse

rating listed above.

A fuse or other protection must be included in all live connections to the
AC supply.
For a parallel DC bus system the maximum AC input fusing is shown in
Table 13-20 below.

Table 13-20 Maximum AC input fusing

Refer to the supplier of your drive for further information regarding DC
bus paralleling.

Inrush current

The drive will have an inrush current during power-up, the peak inrush is
limited to the value shown below:
DST120X 18 A peak
DST140X 35 A peak

The inrush current for all drives after a brown-out can be larger than the
power-up inrush.

13.1.27 Motor cable size and maximum lengths

Since capacitance in the motor cable causes loading on the output of the
drive, ensure the cable length does not exceed the values given in Table
13-21.
Use 105

C (221

F) (UL 60/75

C temp rise) PVC-insulated cable with

copper conductors having a suitable voltage rating, for the following

power connections:
•

AC supply to external EMC filter (when used)

•

AC supply (or external EMC filter) to drive

•

Drive to motor

•

Drive to braking resistor

•

When operating in ambient >45

C UL 75

C cable should be used.

Cable sizes are given for guidance only and may be changed depending
on the application and the method of installation of the cables.
The mounting and grouping of cables affect their current capacity, in
some cases a larger cable is required to avoid excessive temperature or
voltage drop.
Input cable sizes should generally be regarded as a minimum, since
they have been selected for co-ordination with the recommended fuses.
Output cable sizes assume that the maximum motor current matches
that of the drive.
Where a motor of reduced rating is used the cable rating may be chosen
to match that of the motor.
To ensure that the motor and cable are protected against overload, the
drive must be programmed with the correct motor rated current.
•

Cable lengths in excess of the specified values may be used only
when special techniques are adopted; refer to the supplier of the
drive.

•

The default switching frequency is 6 kHz.

The drive power terminals are designed for a maximum cable size of
4.0mm

(minimum 0.2mm / 24 AWG).

Where more than one cable per terminal is used the combined
diameters should not exceed the maximum.
The terminals are suitable for both solid and stranded wires.

Table 13-21 Motor cable size and maximum lengths

13.1.28 Braking resistor values

Table 13-22 Minimum resistance and power ratings

* Resistor tolerance: ±10 %

Model

Fuse rating

IEC class gG

Fuse rating

class CC

Input cable size

AWG

All