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Series Soft Starter Device

Series soft starter device is designed to perform consecutive start of several HV motors be means of a single thyristor-based controller.



Series soft starter device (SSS) is designed to perform consecutive start of several HV motors be means of a single thyristor-based controller.


  • SSS is used across variety of industries and is designed to consecutively start several motors in a soft manner.
  • Application of SSS:
  • Water supply utilities: pumps for water lifting/pumping station, compressors/fans for aeration stations
  • Compressors for metallurgy and automobile factories
  • Compressors for blast furnaces
  • Factory ventilation systems
  • Sledgehammers/presses
  • Water intake pumps for thermal power plants
  • Compressors for gas-based thermal power plants
  • Pumps for heating systems
  • Concrete mills/mills for ore-dressing plants
  • Sludge pumps for ore-dressing plants
  • Oil-transfer/separator pump stations
  • Slush pumps
  • Shaft ventilation
  • Conveyors for mines
  • Compressors for pulp and paper plants
  • Crushing machines
  • Shipbuilding
  • Etc.


SSS consists of three main parts:

1. Soft starter

Soft starter is a thyristor controller that features motor soft start/stop functions. Solcon HRVS-DN thyristor controller is used as the main unit of the device.

2. Switchgear rated for voltage 6 or 10 kV

The basic switchgear unit is the ELTIMA switchgear manufactured by OOO Electronmash Engineering ELTEMA switchgears are intended to receive and distribute AC 3-phase 50 Hz electric power, rated for 6-10 kV isolated or grounded grids via an arc-suppression reactor or a resistor.

3. Control cabinet (CC)

Control cabinets produced by Electronmash JSC are designed for centralized control of starting a number of HV asynchronous motors by means of a single soft starter.

Series Soft Starter - Specifications

Parameter Parameter value
Number of motors As required
Time between starts 30 minutes as standard; higher power soft starter leads to reducing time < 30 minutes
Auxiliary circuits voltage 220 VDC

ELTEMA switchgear - Specifications

Parameter Parameter value
Rated voltage (kV) 6; 10
Maximum operation voltage (kV) 7.2; 12
Busbar rated current (A) 630; 1000; 1250; 1600; 2500; 3150
Rated current of main circuits (A) 630; 1000; 1250; 1600; 2500; 3150
Rated tripping current of the circuit breakers integrated to switchgear (kA) 12.5; 16; 20; 25; 31.5; 40
Short-time withstand current (amplitude) (kA) 51; 64; 81; 102
Short-time thermal current (kA) 20; 25; 31.5; 40
Short-time thermal current duration (s)
- Main circuits – Ground circuits

Rated voltage of auxiliary circuits (V)
- Control and alarm circuits – Light and heating – Electromagnetic interlocks

100 AC, 110 DC, 220 AC/DC
220 AC
220 AC/DC
Cabinet dimensions (mm)
- Width
- Depth
- Height

650; 750; 800; 900; 1000
1400; 1500
2100 - 2400
Weight (kg) Over 480

Schematics Example of a solution based on HRVS-DN controller intended to start three motors:

Series soft starter for starting 3 motors  
Common starting bus  

Principle of operation Serial soft starter will be used as an example. This solution allows for starting up of up to 3 motors in soft mode with a set time delay between the starts. Time delay (pause) between starts is required for thyristors of the soft starter to cool down. By default the time delay is set to 30 minutes. This time delay can be reduced by overrating soft starter power. When starting a motor connected to section I, the soft starter is supplied from the feeder number 3. When starting a motor connected to section II, the soft starter is supplied from the feeder number 6. When power is applied to the soft starter, appropriate cell of the starting bus is switched on which results in soft acceleration of motor. When steady speed has been reached, appropriate motor bypass cell is switched on whilst the starting cell is switched off. Once the starting cell is off, power is removed from the soft starter for it to cool down during the set time delay. Once the timer has expired and thyristor temperature is down, the soft starter is ready to start next motor. SSS is controlled by the system enclosed in Control Cabinet. All signals from cells and from soft starter are connected to the Control Cabinet. Motors can be started locally (by means of door controls), and remotely (near a machine). Series soft starter is controlled by means of operator panel, mounted on the door of Control Cabinet. Should the soft starter run out of order it is possible to run a motor directly, and for mission-critical objects two soft starters are used – one starter is the main unit, another one is the cold redundant unit.

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