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
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 |
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.
Which motors are available for which compressors can be found in the following documents:
In the terminal box cover of the Bitzer compressors, an adhesive label shows the intended electrical connection or starting mode:
![Terminal box of a Bitzer reciprocating compressor. The adhesive label in the cover shows i.a. the correct connection of the mains phases to the motor pins for star-delta start and direct-on-line start in delta and star wiring (from left to right).](../Images/jpg/388225035__Web.jpg)
Schematic wiring diagrams for Bitzer compressors are compiled in the Technical Information AT-300.