High-voltage frequency converters

High-voltage frequency converters (hereinafter referred to as HVFC) are intended for frequency starting and speed control of asynchronous (HVFCA series) and synchronous (HVFCS series) electric motors with power from 315 kW to 20 MW, with rated voltage of 3, 6 and 10 kV, ensuring the operation of technological devices various purposes such as:
- pumps,
- draft equipment,
- compressors,
- mills
and others

OPTIONS:
- Vector control
- Power unit bypass
- Braking resistors
- The reactor for the implementation of the synchronous transition to direct power from the network
- Rated voltage at the input - 10 kV, at the output - 6 kV
- Single-sided/Double-sided version*
- Single-chamber/double-chamber version*

* For certain models

Name of the characteristic	Value
Power	from 400 kVA to 25 MBA
Power of the corresponding engine	from 315 kW to 20 MW
Rated output current, A	from 31 to 1450
The method of forming the output voltage	multi-level pulse-width modulation
Frequency at the input, Hz	from 45 to 55
Frequency at the exit, Hz	from 0 to 60 **
Frequency step, HZ	0.01 (0.002 for vector HVFC)
Acceleration/deceleration time, s	from 5 to 3600
Rated voltage at the input, kV:	3, 6, 10, with a tolerance of: (-10%+10%) - with preservation of nominal characteristics of HVFC; (-30%+10%) - with preservation of the HVFC performance; (–20%+10%) - with preservation of HVFC performance, with a load of not more than 80%
Power factor at the input	at rated load - not less than 0.96
Efficiency in nominal mode	not less than 0.96 (including transformer)
Motor current overload capacity (determined relative to the motor current setting)	120% - 2 minutes, 150% - without time delay
Overload current capacity of HVFC	150% - without time delay
Analog input/output, type 4-20mA	3 channels / 4 channels: - output frequency; - output current; - two programmable outputs.
Discrete input/output signals	13 input / 13 output
External communication	13 input / 13 output
Operator interface	touch graphics monitor, 10.2 inches
Ambient temperature, °C	from minus 5 to plus 45**
Cooling method	Forced air (liquid-cooling system - at rated current of HVFC above 800 Amps)
Degree of protection	IP30** according to GOST 14254-96

** In agreement with the customer, the parameter may differ from the specified.

significant energy savings (up to 60%);
reliability of operation and extension of the service life of electric motors, as well as the units and mechanisms driven by them;
eliminating the occurrence of hydraulic shocks in the piping system and the failure of gear or belt transmission mechanisms;
reducing the accident rate of equipment and reducing the cost of repairs and maintenance, as well as reducing emergency production downtime;
integration into the automatic process control system of the enterprise.

HVFCA converts three-phase AC power supply with voltage of 3, 6, 10 kV with constant frequency and voltage parameters into three-phase voltage with variable frequency and voltage parameters according to the law of frequency control U/f = const.

HVFC high-voltage frequency converters are supplied to the Customer in the form of functionally complete equipment, which includes:
1. A transformer cabinet containing a high-voltage multi-winding transformer of dry type with a special design;
2. Power cabinet and control cabinet containing power blocks with IGBT transistors and HVFC control and monitoring system.

Transformer cabinet

A dry multiwinding transformer is installed in the transformer cabinet of the HVFCA frequency converter, the secondary windings of which have the same value of the voltage phase shift of the next group relative to the previous group of windings.

Each group generates a three-phase supply voltage for one power unit.

In front of the transformer, there are terminals on the right side for connecting power unit cables. Cables connecting the three-phase power supply to the power units are connected to these terminals.

An indicator of a transformer temperature sensor is installed on the cabinet door, providing temperature control, alarms and overheating protection.

On the outer side of the cabinet door, there is a special filter layer, passing through which air is filtered and gets inside the cabinet.

The back walls of the cabinet are easy to dismantle, providing quick and convenient access.
On the inside of the cabinet door, there is a set limit switch.
When the door is opened, the limit switch is activated, triggering the alarm.
Centrifugal cooling fans are installed at the top of the cabinet.
The heated air is drawn out of the cabinet to the outside.
For additional ventilation of transformers, additional fans are installed in the lower part of the cabinet, one on both sides of each core.

Power units and control cabinet

In the power units and control cabinet of the high-voltage frequency converter HVFCA, the power blocks with IGBT transistors and the control system of the HVFC are installed.

Power units are divided into three groups.
In each group, the power units are connected in series in the same row and constitute one phase. Three rows of power units are connected via wye configuration (Y).
Power blocks are installed on special shelf-guides and fastened with screws. The power units installed inside the cabinet have exactly the same electrical and mechanical parameters, and are completely interchangeable.
Three-phase power is supplied to the power units from the secondary windings of the power transformer. Power units are protected by fuses.
The power units are connected in series, forming phase groups. One output of each phase group is connected to one point, thus forming the center of the wye configuration. The second output is directly the output of the HVFCA to the engine.

Each power unit has a separate control panel and driver. Power is supplied from the main DC circuit. Normal operating voltage is 450 - 1250 V DC. The driver is used to control the IGBT transistors and the thyristor of the bypass of the power unit. The control panel is connected to the fiber optic hub system through a fiber optic cable. Fiber optic cable is the only communication channel between the main control panel and the power unit, thereby achieving absolute electrical isolation of the power unit from the main control panel of the system.
In order to remove the power unit, it is necessary to unscrew the fastening screws, disconnect the suitable and outgoing cables, fiber optic cable. After that, you can remove the power unit from its cell. Install the power unit in the reverse order. To do this, you need to put it on the guides, slightly push it in all the way in, fix it with screws, connect the incoming and outgoing cables, insert the fiber-optic cable.
Power units differ depending on the rated voltage and power of the frequency converter.
On the inside of the cabinet door, there is a set limit switch.
When the door is opened, the limit switch is activated, triggering the alarm.

On the outer side of the cabinet door, there is a special filter layer, passing through which air is cleaned and gets inside the cabinet to cool it down.
An exhaust air duct is provided on the back of the cabinet. Cold air passes through the filter layer in the front door and blows through the radiators of the power units. The heated air is pulled out to the back of the cabinet and is brought out by a centrifugal fan.

It is possible to install an uninterruptible power supply for own needs circuits inside the frequency converter.

Control system

A terminal with an industrial LCD display is installed on the front side of the power and control cabinet. The user interface is made in Russian.

The main user interface window displays the HVFC operation parameters, including the target and current output voltage frequencies, input power, voltage, and current, as well as output power, voltage, and current.

The operator has the ability to monitor and local control the engine connected to the HVFC, start and stop, adjust its speed by changing the operating frequency. The possibility of PID control of a technological parameter (for example, pressure) for a given value can also be implemented.

The sinusoidal distortion factor of the input mains voltage and output voltage when the HVFC is less than 5% (in accordance with GOST 13109-97) without the use of additional filters.

Industrial LCD display provides a convenient interface with the operator, allows you to monitor and change the parameters of the frequency converter, controls the HVFC in the local mode.

Wiring for HVFCA "into break"

Circuit with automatic bypass

The operation of the high-voltage frequency converter ensures soft start and control of engine speed in accordance with the technological task, taking into account feedback from the technological parameter sensor, stopping the unit in accordance with a predetermined algorithm from the operator’s console, directly from the unit (from the remote control) or from the APCS control panel, as well as automatic switching of the engine power from the network in case of emergency shutdown of HVFCA or its improper work.

Cascade control scheme

Cascade control scheme of the n-th number of motors by means of a single high-voltage frequency converter, with the possibility of automatic switching of the motor to the nominal mode of operation for direct power supply from the mains and output of a part of the motors according to the established algorithm to the standby mode.

Cascade control scheme

The group control station (GCS) provides an algorithm for correctly switching on the engines and bringing one of the engines to standby mode.
The operation of the HVFCA provides a smooth start-up and control of the engine speed in accordance with the technological task of the GCS.
GCS ensures the maintenance of the regulated parameter in accordance with the technological task and taking into account the feedback from the selected sensor of the technological parameter.

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