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VLT® PTC Thermistor Card MCB 112
Operating Guide
4.4.5 Maximum Motor Frequency
Do not exceed the maximum allowable output frequency. The motor data sheet or nameplate shows the maximum allowed value.
This value can be reduced for long motor cables, sine-wave filter, or reduced supply voltage.
U
− U
n
loss
f
=
× f
max
n
U
n
Use the result from the equation as the value set in parameter 4-19 Max Output Frequency.
Example
Nominal voltage = 480 V
Nominal frequency = 50 Hz
Voltage loss due to supply voltage of 450 V = 30 V
Resulting maximum frequency = 47 Hz
4.4.6 Minimum Switching Frequency
It is mandatory to compare the minimum switching frequency requirement of the motor to the minimum switching frequency of
the drive, which is the default value in parameter 14-01 Switching Frequency. If the drive does not meet this requirement, use a
sine-wave filter.
Thermal motor losses increase with the lower switching frequencies. Ensure that the drive switching frequency does not drop below
the value stated by the motor manufacturer.
4.4.7 Disable Protection Mode
In protection mode, the drive derates the switching frequency below the default in parameter 14-01 Switching Frequency. For exam-
ple, if the default value is 3 kHz, it can derate down to 2.5 kHz, depending on EEPROM.
Therefore:
1.
Disable protection mode in parameter 14-26 Trip Delay at Inverter Fault.
More information about derating can be found in the section Derating in the drive-specific design guide.
4.4.8 Safe Torque Off Functionality
The desired Safe Torque Off functionality is specified in parameter 5-19 Terminal 37 Safe Stop. When a VLT
112 is mounted, select 1 of the PTC options to get the full benefit from the alarm handling. Options [4] PTC 1 Alarm and [5] PTC 1
Warning are relevant when the MCB 112 is the only interrupt device using STO. Options [6] PTC 1 & Relay A to [9] PTC 1 & Relay W/A
are relevant when other safety sensors are also connected to STO.
•
Alarm: The drive coasts. Reset the alarm manually (via bus, digital I/O, or by pressing [Reset]). Auto reset does not apply here. For
more details, see [4] PTC 1 Alarm in parameter 5-19 Terminal 37 Safe Stop.
•
Warning: The drive coasts, but resumes operation when STO and the DI from X44/10 are disabled. Fore more details, see [5] PTC
1 Warning in parameter 5-19 Terminal 37 Safe Stop.
Configuring a digital input in parameter group 5-1* Digital Inputs makes it possible to give a warning/alarm that specifies what trig-
gered the Safe Torque Off.
When selecting a warning instead of an alarm, automatic restart is enabled. See the section Parameter Settings for STO used with
VLT
PTC Thermistor Card MCB 112 in the VLT
®
22 | Danfoss A/S © 2022.08
N O T I C E
N O T I C E
N O T I C E
Frequency Converters - Safe Torque Off Operating Guide.
®
Commissioning
PTC Thermistor Card MCB
®
AQ267038105120en-000101 / 130R0104
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