Introduction

This document gives an overview of the starting modes for Bitzer compressors. The reason for developing different starting modes for larger motors is the high starting current when they are operated and switched on directly at the mains connection (direct-on-line start): At the moment of switching on, starting currents occur that can be several times the nominal operating current (typically: 600 ... 800%) and both load the motor and disturb the power supply system. To avoid this, different methods are used in refrigeration systems to limit the starting current. The following are presented in this document:

• Start with frequency inverter (FI)
• Start with electronic soft starter (ESS)
• Direct-on-line start in star or in delta wiring (Y or Δ)
• Star-delta start (Y/Δ)
• Part winding start (PW start, Y/YY or Δ/ΔΔ)

Some of these starting modes may be combined with start unloading (Additional start unloading (SU)). Further starting modes such as resistance start are not mentioned here, because they are not intended for Bitzer compressors.

For further information read and observe the operating instructions for the respective compressor!

Methods to reduce the starting current for Bitzer compressors

Motors in Bitzer compressors and possible methods to reduce the starting current
: starting current not reduced
: starting current significantly reduced
: starting current strongly reduced

Type of motor	Start with FI	Start with ESS	Direct-on-line start in Y or Δ wiring	Y/Δ start	PW start
Y or Δ motor				not possible	not possible
Y/Δ motor					not possible
PW motor				not possible
LSPM motor				not possible	not possible
Link to chapter	Start with FI	Start with ESS	Direct-on-line start Y or Δ	Y/Δ start	PW start

The LSPM motor consists of an asynchronous motor part for starting and a synchronous motor part for normal operation. Due to the limited space in the rotor, the size of the asynchronous motor is also limited, as is the starting current and the starting torque. During the start, the synchronous motor part generates a torque opposite to the starting torque of the asynchronous motor. If the asynchronous part of the torque is reduced further, the motor will not start. A significantly reduced starting current of the LSPM motor is therefore only possible with a frequency inverter, not with a soft starter.

In the terminal box cover of the Bitzer compressors, an adhesive label shows the intended electrical connection or starting mode: