QUATROFREM 400 110 for a crane drive in permanent operation

The customer needed a conceptual drive solution so that, using frequency converters, the energy generated during the regenerative operation of the crane motors could be fed back into the grid. For this, the most powerful crane drive — the hoist drive — is handled by a QUATROFREM 400 110 regenerative converter, where the input regenerative controlled rectifier also supplies two inverters for the trolley and travel drives. The DC circuits of the QUATROFREM and the other two inverters are interconnected, so when one of the drives works in the regenerative region, the generated energy is either consumed by the other drives or the QUATROFREM's regenerative rectifier automatically feeds it into the supply grid. The QUATROFREM's controlled rectifier of course draws only sinusoidal current from the supply grid and feeds only sinusoidal current into it. The sinusoidal current has a minimal content of higher harmonics — THDi is below 3%. Because with the classic solution using braking resistors the „regenerated energy“ is irretrievably lost — converted into heat — the solution described above is energetically incomparable and is advantageous especially for high-power crane drives in continuous, permanent operation.