SIMOREG 6RA70 Siemens DC Master Variable Speed DC Drive
Design & Mode of Operation
Closed-Loop Functions in Field Circuit

Design and Mode of Operation6RA70 DC Master

Closed-loop functions in field circuit


The EMF controller compares the EMF (induced motor voltage) setpoint and actual value and specifies the setpoint for the field current controller, providing an EMF-dependent closed-loop field-weakening control. The EMF controller operates as a PI controller, the P and I components can be set independently of one another. The controller can also be operated as a pure P or pure I controller. A feedforward control operates in parallel to the EMF controller. This applies feedforward control as a function of speed to the field current setpoint by means of an automatically recorded field characteristic (see optimization runs). An adding point is located after the EMF controller, at which additional field current setpoints can be entered via a connector, e.g. analog input or serial interface. The limitation for the field current setpoint is then applied (maximum and minimum setpoint limits can be set independently of one another). The limitation is implemented via a parameter or connector, in which case the minimum is applied as the upper limit and the maximum for the lower limit.

Field-current controller

The current controller for the field is a PI controller with independent settings for Kp and Tn. It can also be operated as a pure P or pure I controller. A feedforward control operates in parallel to the field current controller. This calculates and sets the firing angle for the field circuit as a function of current setpoint and line voltage. The feedforward control supports the current controller and ensures a good dynamic response in the field circuit.

Gating unit

The gating unit generates the gate pulses for the power section thyristors in synchronism with the line voltage in the field circuit. Synchronization is measured on the power section and is not therefore dependent on the electronics supply. The gate pulse position timing is determined by the output values of the current controller and feedforward control. The firing angle setting limit can be set in a parameter. The gating unit is automatically adjusted to the connected line frequency within a frequency range of 45 to 55 Hz.

SIMOREG 6RA70 Siemens DC Drive Converter Family.

SIMOREG 6RA70 Siemens DC Drive Converter Family.

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Siemens Energy & Automation
SIMOREG DC Master Base Drive Operating Instructions

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