Application with Bitzer compressors

Motors for direct-on-line start in star or delta wiring (star or delta motors, Y or Δ motors) are used in some smaller compressors, they are e.g. standard in:

reciprocating compressors 2KES .. 4BES, 2NSL .. 4CSL, 2MME .. 4DME, 2MTE .. 4KTE
scroll compressors (these are internally star wired, there is only one nominal voltage each - special voltage motors are available for other grids)

Suitable Bitzer motors for direct-on-line start in star or delta wiring

For direct-on-line start in star wiring those motors are suitable in principle which are marked in the Technical Information KT-410 or ST-410 with motor code "..S" and motor connection "Y":

Example from KT-410 for compressors 2KES .. 4BES: The 50S motor is suitable for direct-on-line start in star wiring.
Voltage range (V)	Nominal voltage (V)	Motor code	Motor connection	Nominal voltage (V)	Voltage range (V)
50 Hz				60 Hz
500-550	500	50S	Y	575	575-660

For direct-on-line start in delta wiring those motors are suitable in principle which are marked in the Technical Information KT-410 or ST-410 with motor code "..D" and motor connection "∆":

Example from KT-410 for compressors 2KES .. 4BES: The 20D motor is suitable for direct-on-line start in delta wiring.
Voltage range (V)	Nominal voltage (V)	Motor code	Motor connection	Nominal voltage (V)	Voltage range (V)
50 Hz				60 Hz
180-200	200	20D	∆	200	200-230

For a given compressor, an adhesive label in the terminal box cover shows the possible starting modes.

Starting current for the design of direct-on-line start in star or delta wiring

The starting current shown in the Bitzer Software refers to the measured starting current when the rotor of the three phase motor is blocked (mean value of the currents in L1, L2 and L3, measured simultaneously after 4 s). This starting current (locked rotor) refers to the RMS value (root mean square value): To calculate it, the peak value of the corresponding alternating variable (here current) is divided by √2.

If the motor starts directly in star or delta wiring, these are the maximum starting currents to be expected. However, the first measured amplitude may be larger due to the high unbalances.

Information in the Bitzer Software

If a specific compressor is selected in the Bitzer Software, the available motors are displayed under "Power supply" - "Power voltage" according to the specified supply frequency (additional motors for North America (UL) under "60Hz UL"). The standard motor is preselected.

The selection corresponds to the specifications in the Technical Information on motor codes (KT-410 for reciprocating compressors, ST-410 for screw compressors, EST-410 for scroll compressors).

All further information concerning the motor can be found in the tab "Technical Data" under "Motor data":

Available motors and motor data for reciprocating compressor 4DES-5Y. "Starting current (Rotor locked)" indicates the measured current (root mean square, RMS) when the rotor is locked.

Arrangement of the wiring in the terminal box of the compressor

WARNING

Risk of electric shock!

Before performing any work in the terminal box: Switch off the main switch and secure it against being switched on again!

Close the terminal box before switching on again!

In the terminal box cover of Bitzer compressors, an adhesive label shows the possible starting modes and the respective connection of the mains phases to the motor pins. For a direct-on-line start, the cable bridges supplied may have to be mounted.

Zoom

Motor connection for direct-on-line start in star (Y) or delta (Δ) wiring for reciprocating compressors 2KES .. 2CES (example)

Zoom

Motor connection for direct-on-line start in star (Y) or delta (Δ) wiring for reciprocating compressors 4FES .. 4BES (example)

Schematic wiring diagrams

In the schematic wiring diagram a direct-on-line start in star wiring is depicted like this, for example:

Direct-on-line start in star wiring for a reciprocating compressor
K1: main contactor
M1: motor
R1 .. 6: temperature sensors in motor winding

A direct-on-line start in delta wiring is depicted like this, for example:

Direct-on-line start in delta wiring for a reciprocating compressorK1: main contactorM1: motorR1 .. 6: temperature sensors in motor winding — Direct-on-line start in delta wiring for a reciprocating compressor
K1: main contactor
M1: motor
R1 .. 6: temperature sensors in motor winding

Schematic wiring diagrams for Bitzer compressors are compiled in the Technical Information AT-300.