Soft starter consists of a number of anti-parallel thyristors- 2 per phase. On applying voltage across these thyristor banks and varying the firing angle the voltage at the output can be reduced. This reduced voltage is applied to the motor terminals to achieve a lower starting current and thereby lower starting torque. The firing angle is gradually changed to increase the output voltage to full voltage thereby also gradually increasing the starting current as well as the starting torque without any peaks.
Soft starters can generally be used for applications in the low to high power range (1.1 kW to 1200 kW). The modern design and state-of-the-art technology have made the new age soft starters – Stronger, Smarter, Superior, Safe and Efficient.
Benefits with the Modern, Functionally Dense Soft starters
Enhanced Safety with STO (Safe Torque Off)
The safety function “Safe Torque Off” (STO) in Fail safe variants of soft starter interrupts the current operating state immediately on activation and coasts it down to ensure Safety-related shutoff acc. to EN 61800-5-2 and stop category 0 acc. to EN 60204-1.
This thus effectively ensures that the motor no longer provides any torque-generated energy in the event of an emergency. The motor comes to a standstill and remains safely in this state until it is restarted (restart interlock). The STO facilitates risk-free working, even when the protective door is open, making it popular in process machine applications and systems such as agitators or belt conveyors.
This can be deployed for safety requirement up to SIL3 level which is the industry benchmark for machine safety.
Integrated self-learning with Auto-parameterization for Faster adaptation
Automatic parameterization simplifies the operations in 2 ways – one while commissioning and other while operation of critical applications having highly dynamic load characteristics. This is especially useful in applications like conveyors. The built-in smart processor of soft starters automatically detects and optimizes the individual starting parameters, and also adjusts the current limiting factor in case of varying conditions for an optimal jerk free, belt start – this all without manual intervention.
Thus Auto-parameterization is very useful while commissioning and helps in auto adjustment of parameters for dynamic loads
Pump cleaning and pump stopping
Pumps are used in a wide variety of applications for distribution of liquids. There are 2 major factors that affect the pumping performance – Hammering and Clogging.
When pumps in public water supply systems such as for buildings or pumping stations are working with large volumes of water, switching them off is a challenge. Due to their design, these pumps stop immediately, which can lead to water hammering on pipes, couplings, valves and seals due to the kinetic energy of the mass of water in the piping system.
Similarly, when used in wastewater applications, dirt and particles can cause deposits to build up on the impellers of the pump and reduce flow rates and productivity. This can be avoided with the pump cleaning function of the soft starters. With the integrated measuring systems of the state-of-the-art soft starters – detection of contamination is possible early, and by changing the direction of rotation of the pump back and forth the soft starters prevent blocking.
This function is very useful in process plant and waste management plants where there are chances of clogging.
The modern design soft starters like SIEMENS 3RW5 have a pump stopping mode that allows pumps to come to a standstill in a controlled manner thereby preventing damage to pump and pipes.
Condition Monitoring and Predictive Maintenance
No machine operator would desire unplanned downtime as it hugely impacts productivity, efficiency and wastes of time. To ensure maximum availability and reduce breakdowns the integrated condition monitoring function of soft starters monitors the status of the complete application – which is driven by the motor, in order to be able detect possible wear of the machine and plan a correspondent maintenance work in advance.
Depending on application type – a user can set different warnings and error limits.
For the plant maintenance team, sufficient time is now available to plan a schedule maintenance work.
Smooth Start with Soft torque
When motors start or stop abruptly, mechanical impacts in the machine or voltage dips in the power supply may cause serious problems. These must also be avoided in safety areas.
Soft Torque is a new function that considerably reduces the torque peak before reaching the rated speed of the motor. With this limitation on torque peaks, the mechanical stress of the machine is reduced.
Thus, the overall system availability also increases, and the maintenance intervals are reduced. Soft Torque works also during the stopping procedure, which makes it a good feature to use for pumping applications.
User Account Management (UAM) for Better Administration and control
Enhanced security is ensured when there is a possibility for the user to create various accounts in the starter with individual usernames & passwords for multiple roles having different authorization levels for access, controls, and management.
Selecting the right Soft Starter
There are multiple and readily downloadable configurators that can help in selecting the right soft starter. Siemens Simulation Tool for Soft Starters (STS) eases out the otherwise cumbersome soft starters selection process by simulating the specific – application along with the site conditions and generating results that are easily integrable in almost all the common engineering tools. The working interface of these configurators are simple, intuitive, quick, and easy-to-use.
The major advantages these configurators offer their users are the dual benefit of integrated manufacturer’s motor data and multiple load curves to pick from for the best engineered and simulated output.
Is your solution FUTURE ready?
Industry 4.0 has harbingered digital transformation across industries in full swing. With process and workspace digitalization – the need to have sustainable, communicable & cross device Integrable, efficient and a secure solution is a must.
To fully exploit the potential of digitalization we need to have data – from the field devices. And for this the modern range of devices should be Smart and Communicable.
The latest generation of soft starters like SIEMENS 3RW5 – support rugged and secure industrial communication protocols like PROFINET, PROFIBUS, Ethernet, Modbus … and can transfer data to Mindsphere and other cloud-based services, enabling flexible use both directly at the switchgear as well as at the management level.
This ensures ready availability of machine and plant data at all times, delivering greater transparency, increasing cost-effectiveness, avoiding untimely and unplanned plant downtimes and gives you as a user the benefit to access the operating data across all systems, and use it for further analysis. The results are protected against manipulation and can be used for predictive maintenance, energy data management and resource optimization.
The new generation Soft starters with the increased functionality are now ready to revolutionize the modern-day productivity and workflows.
Spardha Gupta is a Product Manager for Soft Starters at Electrical Products, Smart Infrastructure, Siemens Limited.
