60
Digitax HD M75X Series Installation and Technical Guide
Issue Number: 5
4.8.3 Braking resistor software overload protection
The drive software contains an overload protection function for a braking resistor. In order to enable and set-up this function, it is necessary to enter
three values into the drive:
•
Braking Resistor Rated Power
(10.030)
•
Braking Resistor Thermal Time Constant
(10.031)
•
Braking Resistor Resistance
(10.061)
This data should be obtained from the manufacturer of the braking resistor.
The brake resistor thermal time constant (Pr
10.031
) is used to limit the energy dissipated in a resistor when braking overload energy. For the Digitax
HD M75X drives, the brake resistor thermal time constant should be set to a maximum of 2 seconds. This will protect both the drive and the brake
resistor from excessive temperatures. Full overload and continuous braking levels are achievable with this setting.
Pr
10.039
gives an indication of braking resistor temperature based on a simple thermal model. Zero indicates the resistor is close to ambient and
100 % is the maximum temperature the resistor can withstand. A ‘Brake Resistor’ alarm is given if this parameter is above 75 % and the braking IGBT
is active. A Brake R Too Hot trip will occur if Pr
10.039
reaches 100 %, when Pr
10.037
is set to 0 (default value) or 1.
If Pr
10.037
is equal to 2 or 3, a Brake R Too Hot trip will not occur when Pr
10.039
reaches 100 %, but instead the braking IGBT will be disabled until
Pr
10.039
falls below 95 %. This option is intended for applications with parallel connected DC buses where there are several braking resistors, each
of which cannot withstand full DC bus voltage continuously. With this type of application it is unlikely the braking energy will be shared equally
between the resistors because of voltage measurement tolerances within the individual drives. Therefore with Pr
10.037
set to 2 or 3, then as soon as
a resistor has reached its maximum temperature the drive will disable the braking IGBT, and another resistor on another drive will take up the braking
energy. Once Pr
10.039
has fallen below 95 % the drive will allow the braking IGBT to operate again.
See the
Parameter Reference Guide
for more information on Pr
10.030
, Pr
10.031
, Pr
10.037
and Pr
10.039
.
This software overload protection should be used in addition to an external overload protection device.
4.9 Ground leakage (PE current)
The ground leakage current depends upon whether the internal EMC filter is installed or not. The drive is supplied with the filter installed. Instructions
for disconnecting the internal filter are given in section 4.10.3
Table 4-13 Ground leakage with and without Internal EMC filter installed
* These are RMS values within a 1.5 kHz bandwidth measured with a configuration of 2 m SY cable connected to a common 4 pole motor cable at a
switching frequency of 8 kHz having the motor frame only connected to the ground potential through the motor cable. Refer to the Digitax HD M75X
series EMC data sheet, available from the supplier of the drive.
4.9.1 Use of residual current device (RCD)
There are three common types of ELCB / RCD:
1. AC - detects AC fault currents
2. A - detects AC and pulsating DC fault currents (provided the DC current reaches zero at least once every half cycle)
3. B - detects AC, pulsating DC and smooth DC fault currents
•
Type AC should never be used with drives
•
Type A can only be used with single phase drives
Drive
With internal EMC
filter connected
*
With internal EMC
filter disconnected
*
mA
mA
M75X-0120022
7.7
2.8
M75X-0120040
7.7
2.8
M75X-0120065
7.7
2.8
M75X-0220090
10.9
8.9
M75X-0220120
10.9
8.9
M75X-0320160
8.1
1.6
M75X-0140015
13.9
4.4
M75X-0140035
13.9
4.4
M75X-0140042
13.9
4.4
M75X-0240060
16.5
6.8
M75X-0240080
16.5
6.8
M75X-0240105
16.5
6.8
M75X-0340135
16.3
3.8
M75X-0340160
16.3
3.8
When the internal filter is installed the leakage current is above 3.5 mA. In this case a permanent fixed, low impedance, low inductance
ground connection between the drive’s metal frame and PE must be provided, or other suitable measures taken to prevent a safety hazard
occurring if the connection is lost.
WARNING
Содержание Digitax HD M75 Series
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