Soft start

Smallest 15kW soft-starter for compressors plays by the toughest rules

Carlo-Gavazzi has introduced the industry’s smallest 15kW soft-starter, extending the company’s range of compact modules for compressor applications such as geothermal heat pumps. The new RSBT type complements existing single-phase solutions by offering three-phase control and enhanced inrush current handling, whilst meeting residential Class B EMC requirements without the need for external filters.

Ideal for industrial or domestic applications such as three-phase scroll compressors, the new soft-starter features internal semiconductor by-pass technology and is available with nominal current up to 32A. The module comes in a compact 45mm-wide format for space-conscious panel or DIN rail mounting. Control of all three phases ensures optimum current reduction, along with balanced current on all phases. This is achieved without the need to make front-panel settings.

An innovative self-learning algorithm ensures that optimum starting current performance is achieved at every start. The auto-adaptive software is available as standard on all RSBT variants and works by measuring relevant parameters during ramp-up, storing these values and using them to set new current-limit values for the following start. The goal is to use the smallest inrush current value to start the motor, without exceeding the 600ms maximum ramp-up time.

Optimisation is achieved automatically by the software-starter, so users do not have to adjust external settings and there is no need to make initial settings in the factory. As well as saving time, this eliminates a possible source of operator error. The feature also compensates for higher starting currents that may be required as compressors age, reducing potential problems and start-up alarms. The result is lower down-time and fewer service calls.

This integrated current limit feedback reduces inrush current by up to 65 percent, allowing users to counter escalating energy costs and peak consumption regulations. Moreover, the resulting reduction in component stress extends compressor lifetime, further lowering the cost of ownership.

The soft starter can perform 12 starts per hour; providing significant headroom over the four to six starts typically carried out by heat pumps.

Built-in motor protection capabilities range from transient over- and under-voltage protection, through phase sequence and under-voltage monitoring, to locked rotor protection, over-temperature protection and over-current protection in by-pass mode. Full status indication is provided through an easy to read alarm LED flash sequence. Beyond these vital functions, further facilities are readily added via Carlo Gavazzi’s extensive range of rail-mounted motor control modules.

Designed to comply with the latest, IEC60947-4-2, international motor-starter standards, the RSBT soft-starter is also RoHS compliant, cUL listed and carries appropriate CE marks.