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Illustration 13: Start-up Cabinet
The function of current-limiting resistance is to limit the primary current when a high voltage is connected. Each resistor can bear a
30 kJ energy during the power-up. The capacity of the drive defines how much resistance is needed in the start-up cabinet: the
larger the capacity, the more current-limiting resistors are needed.
The function of the high-voltage switch is to bypass the current-limiting resistor after the powering-up procedure, making the drive
function under normal load. If the rated current is small, a vacuum contactor can be used. If the rated current is large, a vacuum
breaker can be used.
Operation process
Power up the drive.
The control program confirms if the system is ready and if the cabinet switch is separated or not.
Power up the start-up cabinet and the control program counts the time it takes to complete the process. The process requires
about 5 s.
The closing of the start-up cabinet switch bypasses the charged resistor and the drive has status 'running allowed'.
When to select the Start-up cabinet option?
The MCB protection at the installation site must not trip because of the inrush current when the drive is powered up or in normal
overload conditions. The overcurrent protection of the MCB must be set in the grey area shown in Illustration 14.
If the MCB meets these requirements, the start-up cabinet is not required. It is important to verify this condition, especially in retrofit
applications where a circuit breaker is already installed at the motor control center panel.
Even if it is not required, a start-up cabinet can still be installed to:
Reduce inrush current.
Reduce stresses in the electrical installation during the drive power-up operation.
AQ363633621020en-000201 / 172F311722 | Danfoss A/S © 2021.06
Product Overview
VACON® 1000
Operating Guide
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