Direct start star-delta startup

Savings potential by pump control with frequency converter

Pump controls with direct start or star-delta start (depending on pump capacity) are suitable for automatic or manual control of three-phase pumps with functions individually tailored to your needs.

These include, among others:

  • Dry-running protection: Dry-running protection can be realized via an electrode as well as via a float switch.
  • Level control with float switches or electrodes: Two level electrodes or float switches (minimum and maximum level) are installed. If the maximum level is exceeded, the pump starts/stops. When the level falls below the minimum level, it stops/starts again.
  • Control input for remote control: The automatic pump control can be activated or deactivated via a control input (ext. potential-free switched).
  • Fault signal contact: When the motor protection switch is triggered, a potential-free (NC) fault message can be picked up.

Technical data

  • Power (direct start): up to 4kW
  • Power (star-delta start): up to 30kW
  • Voltage: 400V AC
  • individually expandable Rittal AE compact switch cabinet
  • Siemens main switch
  • Siemens motor protection switch
  • Start/stop double push button
  • from 4 kW: Siemens star-delta contactor combination

In general, pump controls with direct start and star-delta start are nowadays considered obsolete. Due to the fixed mains frequency, strongly excessive currents of up to twenty times the rated current occur during start-up, so that a corresponding peak load design becomes necessary, especially for large motors, for which the mains supplier usually pays dearly.

Pump control by means of frequency converters is a cost-effective alternative to upgrading outdated systems. Water and electricity can be saved by using the convenient PID control to deliver water as needed, operating the pump only at the speed and power actually required, which incidentally results in smoother control without large pressure surges. Inverters are much cheaper today than in the past. This means that the controls are also less expensive, and the expenditure for the conversion is quickly amortized.

We therefore recommend always using a frequency converter for new projects and converting old systems that are not only used sporadically to frequency converter operation.