21
ANTRIEBSTECHNIK
; A system should be broadly separated into power section and control section,
whether comprising a single enclosure or multiple enclosures. It is recommended
that a screen wall is installed between the two sections because of the radiated
noise from the power section. This screen must be in good metal-to-metal contact
with the mouting plate (remove galvanized or lacquer finish), over as large an area
as possible.
; The installed inverter and a superposed interference suppression filter must form
a unit, i.e. they must, for example, be connected to each other without an insulating
layer of lacquer and cover the mounting plate evenly.
; The connecting line between interference suppression filter and inverter should be
a shielded line installed on both sides and usually be no longer than 30 cm.
; The mounting plate of the inverter must be seen as the neutral point for the entire
earthing and shield connection in the machine or system. If the motor or other
system parts lead to disturbances, then the HF-connection of these elements is
bad. In this case equipotential bonding must be done.
; A good connection of the shield onto the motor terminal box is only given, when the
terminal box is made out of metal, and a metal cable gland is used to connect the
screen. When using a plastic box, provide the shield without elongation with a cable
lug and connect directly with the earthing point.
; The leakage currents in the circuit increase when interference suppression filters
are used. Since these lie above the 3,5mA threshold, one of the following conditions
must be met:
• Protective conductor section at least 10 mm² copper
• Monitoring of the protective conductor by a device that independently switches
off under fault conditions.
• Install a second conductor electrically parallel to the protective conductor via
separate terminals.
; Place consumers generating electric or magnetic fields or affecting the voltage
supply as far away as possible and take measures to suppress the interference.
; The service life of the frequency converter / servo drive with intermediate voltage
circuit depends on the current load of the electrolytic capacitors in the intermediate
circuit. The use of mains chokes can increase the service life of the condensators
to a considerable extent, especially when connecting to „hard“ power systems or
when under permanent drive load (continuous duty).
For continuous duty (S1) drives with a medium duty of >60% , KEB recommends
the use of mains chokes with a terminal voltage (Uk) of 4%.
The term “hard” mains can be defined as follows:
The inverter’s nominal power (Sn) is very low compared to the nodal point power
(Smains) .
k = Smains / Sn >> 200 e.g. Sn = 6.6 kVA 12.F4
Smains = 2 MVA supply transformer
––> k = 330
––> Choke required
; When using a mains choke, it should usually be mounted on the mains side of the
interference suppression filter.
3.4 Explanations
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