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Vacon NX products for common DC bus systems

Vacon offers a comprehensive range of common DC bus drive products. The product family covers a number of front-end units, inverter units and brake chopper units in the entire power range up to 5,300 kW at 380 VAC to 690 VAC.

The drive components are built on the Vacon NX technology. Common DC bus components are used in a multitude of combinations. In a typical DC bus configuration, the drives which are braking can transfer the energy directly to the drives in motoring mode.

Front-end units

The front-end units convert a mains AC voltage and current into a DC voltage and current. The power is transferred from the mains to a common DC bus (and, in certain cases, vice versa).

The AFE (Active front-end) unit is a bidirectional (regenerative) power converter for the front-end of a common DC bus drive line-up. An external LCL filter is used at the input. This unit is suitable in applications where low mains harmonics are required. AFE is able to boost DC link voltage (default +10%) higher than nominal DC link voltage (1,35x UN).

AFE needs an external pre-charging circuit. However, AFE does not need any external measurements to operate. AFE units can be connected parallel without any special connections between the units. AFE units can be connected to the same fieldbus with inverters, and they can be controlled and monitored via fieldbus.

The FFE (Fundamental front-end) unit is a bidirectional (regenerative) power converter for the front-end of a common DC bus drive line-up. The FFE is a device that operates as a diode bridge for motoring power and like an anti-parallel thyristor bridge for regenerating power. In the FFE unit, IGBTs are used instead of thyristors. A dedicated external choke is used at the input.

The FFE unit is suitable as a rectifying device when a “normal” level of harmonics is accepted but regeneration to the mains is required. There are many benefits when conparing with the anti-parallel thyristor bridges: no autotransformers are needed (for nominal DC link voltage 1,35xUN), max motor voltage is the same as supply voltage without autotransformer, controlled operation in case of supply failure and the spare parts are the same as in the inverter of the same size.

FFE needs an external charging circuit. FFE unit can be connected to the same fieldbus with inverters, and it can be controlled and monitored via fieldbus.

The NFE (Non-regenerative front-end) unit is a unidirectional (motoring) power converter for the front-end of a common DC bus drive line-up. The NFE is a device that operates as a diode bridge using diode/thyristor components. A dedicated external choke is used at the input.

The NFE unit has the capacity to charge a common DC bus. This unit is suitable as a rectifying device when a “normal” level of harmonics is accepted and no regeneration to the mains is required. No external charging circuit is needed because the charging is made by the controlling thyristors. NFE units can be connected parallel without any special connections between the units.

Inverter unit

The INU (Inverter unit) is a bidirectional DC-fed power inverter for the supply and control of AC motors. The INU is supplied from a common DC bus drive line-up. A charging circuit is needed in case the connection possibility to a live DC bus is required. The DC side charging circuit is integrated up to 75 kW (FR4-FR8) and external for higher power ratings (FI9-FI14).

Brake chopper unit

The BCU (Brake chopper unit) is a unidirectional power converter for the supply of excessive energy from a common DC bus drive line-up to resistors where the energy is dissipated as heat. External resistors are needed. By using two brake resistors, the braking power of the brake chopper is doubled.

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