Application:
An unwinder for paper in a reeler-slitter is to be modernized - but the existing motor is to be kept. The power section is to be supplied from the existing 690 V supply. The technological control is to be implemented in the higher-level PCS7 system. The client specified PROFIBUS as the control and setpoint interface. The following measured values and status displays are to be visualized in the drive cabinet door to facilitate fast and simple diagnostics for the service and maintenance personnel: Armature current, armature voltage, speed, field current, status messages - operation and fault.

The customer explained that he repeatedly had problems with the existing converter relating to overvoltage in the motor armature circuit - and as a consequence, this resulted in tension fluctuations in the paper web when the motor goes into the field-weakening range. As a result of instability in the control voltage supply, in the past, there were repeatedly failures that had a negative impact on the availability.

Solution:
As a result of the data of the existing motor and the customer specifications relating to acceleration and braking ramps, tambour roll weight and max. diameter, a four-quadrant converter was selected with a rated supply voltage of 690 V and a rated current of 1 500 A. The dynamic overload capability of the units is utilized to brake the drive when the paper web breaks.

The technological control with current setpoint interface is realized in the higher-level control. This is the reason that for this particular application, the standard CUD is sufficient, which already has an integrated PROFIBUS interface.

The problem with armature overvoltages when entering the field weakening range has now been resolved by selecting the two-quadrant field power section option. By actively reducing the current using a counter-voltage, the field current actual value can now follow the field current setpoint - even for steep acceleration ramps - and therefore overvoltages are avoided in the armature circuit. The tension fluctuations in the paper web are consequentially eliminated.

Selecting the electronics power supply option for connection to 24 V DC and SITOP UPS allows a favorably-priced, low-maintenance DC UPS system to be created.

The requirements regarding actual value and status displays can be optionally realized using pointer-type instruments, or using the Advanced Operator Panel AOP30 included as standard.

Coated PCBs and nickel-plated copper busbars were selected as a result of the aggressive atmosphere with a high percentage of H₂S. Roof sections are available for the cabinets in order to achieve IP21. The motor is equipped with a motor fan, which has a rated current of 4.5 A.

The availability of equipment is extremely important in the paper industry. This is the reason that the option "memory card left" should be selected in addition to allow short downtimes. Firmware and additional languages of the AOP text are saved on this card. Further, parameter values can be additionally saved and there is a reserved memory area for offline long-time trace records, which can be centrally read-out from a control room via routing. Further, the memory card allows DCC to be used, with which a winder application can be implemented.

To commission the application, in the switchgear room, the PC is directly connected to the drive via PROFIBUS. This is a straightforward operation using the "Commissioning interface cabinet door access" option with the cabinet door closed.

The following options must be selected for this particular application:
L05 (electronics power supply for connection to 24 V DC)
L09 (24 V DC supply with SITOP UPS)
L11 (field power section 2Q)
L91 (commissioning interface (PROFIBUS) cabinet door access)
M08 (coated PCBs)
M10 (nickel-plated copper busbars)
M21 (degree of protection IP21)
S01 (memory card left)
W35 (setting range of the motor protection circuit breaker for the motor fan (4.5 up to 6.3 A))

The ordering data are as follows:
6RM8093‑4KV62‑0AA0‑Z
L05+L09+L11+L91+M08+M10+M21+S01+W35