MV Soft Starter System

Why Soft Starter ?

Three-phase AC induction motors are commonly used in a wide variety of drive applications. Due to their starting characteristics, in many cases these motors cannot be connected directly to the power supply system. When starting Direct On Line (DOL) the motor can see a very high surge current reaching up to 6 times (and more…) the rated motor current. This excessive current puts stress on the supply system and the switchgear. Also, when starting DOL, a very high peak torque can occur, stressing the driven motor and the mechanical system including auxiliary power transmission parts (V-belt, gears, etc.).

There are several methods for reducing the damaging effects of this excessive starting current. Conventional methods include reactors and autotransformers. But these methods only allow the voltage to be reduced in steps whereas a soft starter provides step-free acceleration of the drive system by continuously increasing the voltage over a selected period of time. This approach to starting minimizes the effect of high inrush current on the supply system, the motor and the driven load.

Soft starters provide the following benefits:

• Reduced starting current, eliminates voltage drops and dips of the supply network
• Smoother acceleration of loads, eliminates process or product damage
• Extended lifetime of all mechanical components, e.g. eliminates gearbox damage and results in less maintenance & downtime
• Extended motor life
• Reduced maintenance and operating costs

The HRVS-DN soft starter represents a logical extension of the manufacturer soft starter product range into medium voltage applications.

With HRVS-DN, we present an innovative standard product that provides a flexible, low cost alternative to fixed speed (DOL) starting.

Designed for use with standard medium voltage three-phase squirrel cage induction motors as well as synchronous motors, this high-performance digital soft starter ensures smooth acceleration and deceleration.

HRVS-DN is available in all standard internationally recognized medium voltage ratings: 2.3kV, 3.3kV, 4.16kV, 6kV and 6.6kV, 10kV, 11kV, 13.2kV, 13.8kV and 15kV.

The standard current output range capability is from 200kW to 27MW.

HRVS-DN is designed and built to meet international standards including:

•        IEC • EN • DIN VDE • NEMA • UL/CUL • IEEE

The HRVS-DN soft starters are manufactured at the highest quality level. The entire design, production and delivery process, (i.e. construction, manufacturing, order processing and logistics delivery center) have been certified DIN ISO 9001.2000.

How Soft Starters Work?

By using thyristors (SCRs) in a phase angle control mode, reduced voltage control can be achieved. Phase control makes it possible to gradually increase the motor terminal voltage from an initial set point up to the system supply voltage level. The related starting current and the starting torque can be optimally adjusted to the motor/load conditions.

In addition, the HRVS-DN soft starters provide the "soft stopping" function as a standard feature. Similar to the reduced voltage start, a stop command gradually reduces the motor voltage over time until the motor stops. Abrupt stopping is avoided, a specific advantage in pumping applications to prevent the damaging effects of water hammer and on conveyor belts where the load may be damaged by an abrupt stop.

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