High-frequency frequency converters for synchronous motors

The VPC5-IT series high-voltage frequency converter is designed for acceleration and speed control of a synchronous motor.
The converter is configured in accordance with the load commutated inverter diagram, the single-line diagram is shown in next Figure.

Complete circuit diagram and equipment composition

VPC-IT consists of:

  • power thyristor cabinet (PC) 2 pcs.,
  • control cabinet (CC) 1 pc.,
  • lead-in cabinets (LC) 2 pcs.,,
  • DC filter cabinet (DCC) 1 pc.

VPC-IT single-line diagram

On the basis of VPC5-IT it is possible to build starting devices for sequential acceleration of synchronous motors with heavy starting duty or initial acceleration of synchronous generators.
VPC uses a network synchronization and switch to bypass algorithms.

The control system provides for implementation of any object orientation as per customer requirements.
Over a period of 1 year after equipment was put into operation, the manufacturer completes the converter software (technological object orientation software) upon request of maintenance services on the free of charge basis.

The converter software is tailored for the need of a particular customer and specific application of the converter.

The converter supply can be completed with:

  • Synchronous motor exciter of VTE series (link to the section),
  • Cubicles with high-voltage circuit-breakers;
  • Switching cabinets;
  • Harmonic filters for reactive power compensation and elimination of converter’s influence on the network (link to the section);
  • Remote control panels,
  • Automation cabinet.

Application advantages of VPC-IT:

  • simple and reliable conversion scheme;
  • higher efficiency compared to other high-voltage converters;
  • possibile production of a converter for high-powered engines (10 MW or more).

Control system

The features of VPC microprocessor control systems (CS) are as follows:

  • the entire range of VPC has unified Control Systems, which are also consistent with other company products – intelligent control panels, diagnostic systems, remote I / O devices, synchronous motor exciters, turbo- and hydro-generators excitation systems, starters;
  • CS allows for obtainment and processing of signals from any sensors – pulse sensors, encoders, selsins, temperature sensors etc., including sensors with serial communication channels;

VPC control:

  • local control – via press button commands on the VPC control cabinet door.
  • remote control – via contact commands on the drive control panel;
  • remote control – via network interface of Automated Process Control System on the level of workshop, plant, etc.

Interfaces (optional):

  • support of network interfaces such as Profibus DP, Modbus, Ethernet, CAN;
  • flexible structure of the control and regulation system, open for monitoring and control from Automated Process Control System via network interfaces.

Protection and blocking:

  • maximum current protection;
  • overvoltage protection;
  • overload protection in accordance with the name plate, time-current characteristic of motor g tolerance;
  • power circuit disconnection protection;
  • open-phase switching-on protection;
  • extended start protection.
  • protection for no conductivity of thyristors in the converter;
  • automatic reclosing upon decrease and/or power outage;
  • protection against failure of control system power sources;
  • protection against outage or unacceptable drop in station auxiliaries voltage;
  • protection against opening of power cabinet doors under high voltage conditions;
  • blocking for incorrectly assembled switching equipment circuit.

If there is a breakdown of a single thyristor on one side, the control system generates a warning signal, but VPC remains in operation. The breakdown of a second thyristor on the same side causes an emergency shutdown of VPC with corresponding emergency message sent on the console terminal.

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