Circuit arrangement for frequency adjustment of a DC voltage intermediate-circuit converter with a constant output voltage

摘要

In the case of a circuit arrangement for frequency adjustment in the field-weakening range of a three-phase machine (5) which is supplied via a DC voltage intermediate-circuit converter, it is intended to achieve the effect that the three-phase machine always maintains its rotation speed, that is to say even when the amplitude of the output voltage is reduced as a result of mains-voltage reductions. Provided for this purpose is a field-weakening controller (21) to which the control deviation of a control variable (xUD) (which is proportional to the intermediate-circuit voltage) is provided in advance from a reference variable which is emitted by an additional required-value transmitter (14) and is proportional to the magnitude of the mains voltage (UMAINS), and whose output signal is added to the control variable (xUD) (which is proportional to the intermediate-circuit voltage) as an additional variable. The control variable (xUD) (which is proportional to the intermediate-circuit voltage), together with the additional variable, is used on the one hand as a control variable for a frequency controller (13) for which a reference variable (WUD) (which is proportional to the motor rotation speed) is provided in advance and whose output signal controls the mains converter (1) of the DC voltage intermediate-circuit converter, via a subordinate current regulator. On the other hand, the sum of the control variable (xUD) (which is proportional to the intermediate-circuit voltage) and the output signal of the field-weakening controller (21) is supplied to a voltage/frequency converter (25) whose output signal defines the frequency of the machine converter (4) of the DC voltage intermediate-circuit converter. <IMAGE>