DANFOSS has introduced a new and extended version of the VLT 2800 series with a power range including the sizes 11kW, 15kW and 18.5kW.
An extended power range is, how ever, not the only innovation offered by the improved product series.
Danfoss took the opportunity to add a number of benefits, dedicated to industrial applications, without compromising with the well-known compact design.
Among the benefits is a new function – ‘hand-off-auto’.
This new function is actually three functions in one, operated as a one-button control:
Auto(normal mode). The frequency converter is controlled by external reference signals, e.g. current or voltage (0-10V/4-20mA).
Hand. In this mode the application is controlled manually from the frequency converter, ignoring external reference signals. The hand mode is useful for commissioning or in case of error in an external controller/sensor. Transition from Auto to Hand is smooth.
Off. A stop button that can be used for service. Allows the application to be stopped locally, e.g. for changing the parameters.
Harmonic suppression. Thanks to the built-in dc coils link choke, VLT 2800 frequency converters are able to reduce the generation of harmonic distortion, keeping it within the limits of the new EN 61000-3-2 standard, which took effect on January 1.
Besides meeting the requirements of the standard, the reduced currents mean less generation of heat, and they allow a lighter design of cables and transformer, in fact the whole installation. Harmonic suppression efficiently prevents interference of other equipment connected to the same transformer.
RFI switch. This function disables the RFI filter, which is a useful option for IT networks. The switch disconnects the RFI capacitor of the frequency converter, thus protecting it against destruction in case of an earth-fault causing double voltage.
Obviously, RFI is not damped when the filter is off. This is, how-ever, not mandatory for IT networks. The RFI switch is easily operated from the front of the frequency converter.
Emphasising the innovative basis of the extended VLT 2800 series of frequency converters, two construction features have been patented.
Firstly, the cooling profile has been minimised to make the device extremely compact for saving space in panels as well as optional side-by-side mounting.
Secondly, a special inrush circuit on the RFI filter limits the earth leakage inrush current, thus avoiding nuisance trips of residual current devices (RCDs) during power-ups.
VLT 2800 frequency converters can be supplied with Profibus or DeviceNet fieldbus options. As of May 2001, Danfoss will supply a CANopen fieldbus protocol – a much-requested option in many industries.
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