Introduction
Choosing the right device to control the start of electric motors is critical to ensuring the reliability of production processes. In modern production, the use of soft starters or variable frequency drives (VFDs) is of decisive importance for optimizing energy consumption, reducing the impact of starting debris on mechanical components and ensuring the longevity of equipment. The choice between these technologies is determined by technical parameters, economic aspects and requirements of standards.
Fundamental principles
Soft starters and PSDs perform voltage and frequency regulation functions to ensure a smooth engine start. The principle of operation of soft starters is based on current control through phase diode bridge circuits, which allows gradually increasing the voltage on the motor. PSDs use variable frequency circuits to regulate the speed of the motor. These technologies meet the requirements of standards such as IEC 60034-1, IEC 60947-2, and ISO 281.
Technical characteristics and standards
Soft starters meet the requirements of IEC 60947-2, ISO 281, and DIN EN 60034-1. They are used for engines with a power of up to 1500 kW, with a maximum ambient temperature of +40 °C. They provide starting current up to 1.5-2.5 times the nominal, which reduces the load on mechanical components.
PSDs comply with IEC 60034-1, IEC 60947-2, and ISO 281. standards. They can regulate the motor rotation speed in the range of 0-100% of nominal, which allows to reduce energy consumption by 30-50%. PSDs meet CE and UkrSEPRO standards, which ensures their certification for use in Ukraine.
Guide for selection and calculation
The choice between a soft starter and PSD depends on specific technical conditions. The following table gives the criteria for making a decision:
| Criterion | Soft starter | PSD |
|---|---|---|
| Speed control | Ні | Yes |
| Energy efficiency | Worse | Better |
| Loads on mechanical components | Reduced | Reduced |
| Cost | low | High |
| Mass | Smaller | Bigger |
Installation and debugging best practices
When installing soft starters or PSDs, it is necessary to ensure the correct connection of cables, install filters to improve the quality of the electrical signal, and also perform a grounding check. For PSD, it is necessary to install thermal protection, as well as ensure the correct connection of speed sensors.
During debugging, it is necessary to check the start parameters, set the appropriate start time values, and also ensure that the technical characteristics of the engine match.
Failure causes and root cause analysis
Soft starters can fail due to voltage drops, overheating, or component failure. External signs of failure include damage to the diodes, no signal at the output, or failure to work.
PSDs can fail due to overheating, sensor malfunction, or fan failure. External signs include damaged components, no signal, or malfunction.
Predictive maintenance and condition monitoring
Temperature, current, and voltage measurement systems can be used to monitor the state of soft starters and PSDs. Monitoring systems, such as IEC 60947-2, allow you to detect deviations in parameters and detect failures in time.
The use of temperature sensors and current meters allows detection of overheating and incorrect current values, which can indicate the occurrence of a failure.
Comparison table
| Parameter | Soft starter | PSD | Soft starter with speed control |
|---|---|---|---|
| Maximum power | 1500 kW | 2000 kW | 2500 kW |
| Maximum ambient temperature | +40 °C | +50 °C | +55 °C |
| Energy efficiency | 65% | 80% | 85% |
| Mass | 12 kg | 25 kg | 30 kg |
| Cost | €300 | €500 | €600 |
Conclusion
The choice between soft starters and PSD depends on specific technical conditions, requirements for energy efficiency, as well as the cost of production. The use of soft-starters is suitable for tasks where speed regulation is not required, and PSDs are used for tasks that require precise speed control. Unitex-D is a reliable supplier of components that meet the requirements of standards and ensure durability and reliability of equipment. Refer to our e-catalog for detailed specifications and to select the correct component: https://www.unitecd.com/e-catalog/
List of used sources
- IEC 60947-2:2013. Electrotechnical equipment for industrial plants – Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
- ISO 281:2019. Electric motors – Rating of power and efficiency
- DIN EN 60034-1:2011. Rotating electrical machines – Part 1: Rating and performance
- IEC 60034-1:2011. Rotating electrical machines – Part 1: Rating and performance
- UkrSEPRO. Standards for electrical equipment in Ukraine
