Application range

For a safe compressor operation with frequency inverter, the following limiting factors must be strictly observed:

These limits define the application limits and can vary according to frequency ranges and operating conditions.

Speed and frequency ranges

Permitted speed and frequency ranges of Bitzer reciprocating compressors with external frequency inverters and standard motors (also observe the application limits and the maximum current consumption of the motor)
*: Pilot series 30 .. 50 Hz

Compressor

Frequency range (Hz)

Speed range (min-1)

Standard motor

Semi-hermetic reciprocating compressors

Ecoline

2KES .. 2FES

30 .. 70

900 .. 2050

40S

2EES .. 2CES

30 .. 70

900 .. 2050

40S

4FES .. 4BES

25 .. 70

750 .. 2050

40S

4VES .. 4NES

25 .. 70

750 .. 2050

40P

4VE .. 4NE

25 .. 70

750 .. 2050

40P

4JE .. 4FE

25 .. 70

750 .. 2050

40P

6JE .. 6FE

25 .. 70

750 .. 2050

40P

Octagon SL R744 subcritical

2NSL .. 2FSL

30 .. 75

900 .. 2200

40S

2ESL .. 2CSL

30 .. 75

900 .. 2200

40S

4FSL .. 4CSL

25 .. 70

750 .. 2050

40S

4VSL .. 4NSL

25 .. 70

750 .. 2050

40P

Ecoline ME R744 subcritical

2MME .. 2FME

30 .. 75

900 .. 2200

40S

2EME .. 2DME

30 .. 75

900 .. 2200

40S

4FME(M) .. 4DME(M)

25 .. 70

750 .. 2050

40S

4TME(M) .. 4PME(M)

25 .. 70

750 .. 2050

40P

6TME(M) .. 6PME(M)

25 .. 70

750 .. 2050

40P

8VME .. 8PME

30 .. 60*

900 .. 1750*

40D

Ecoline R744 transcritical

2MTE .. 2KTE

30 .. 75

900 .. 2200

40S

4PTE
4MTE(M) .. 4KTE(M)

25 .. 70

750 .. 2050

40S

4JTE(M) .. 4CTE(M)

25 .. 70

750 .. 2050

40P

6FTE(M) .. 6CTE(M)

25 .. 70

750 .. 2050

40P

8FTE .. 8CTE

30 .. 60

900 .. 1750

40D

Ecoline+ R744 transcritical (LSPM)

4PTEU
4MTE(M)U .. 4KTE(M)U

25 .. 70

750 .. 2100

40S

4JTE(M)U .. 4CTE(M)U

25 .. 70

750 .. 2100

40S

6FTE(M)U .. 6CTE(M)U

25 .. 70

750 .. 2100

40S

Open drive reciprocating compressors

2T.2 .. 4G.2
W2TA .. W4GA

750 .. 1750

(external motor)

6H.2 .. 6F.2
W6HA .. W6FA

900 .. 1750

(external motor)

2TFR .. 2NFR

on request

(external motor)

4UFC .. 6NFC

on request

(external motor)

Bitzer has developed the special series Ecoline Varispeed with integrated frequency inverter, where compressor and frequency inverter complement each other optimally (see Operating Instructions KB-100, Technical Information KT-210 and KT-220):

Design at different supply voltages and supply frequencies

If power supply deviates from standard conditions (400 V/3/50 Hz), special voltage motors and adapted frequency inverter design are required (Compressor motors). More information is available upon request.

Application limits

The following figure shows exemplarily the application limits of a reciprocating compressor operated at different frequencies and how they may change with evaporation and condensing temperature. Specific application limits for particular compressors, motors and refrigerants are given in the Bitzer Software.

Example for application limits for reciprocating compressor 4MTE-10 with refrigerant R744 (CO2) and frequency inverter at 50, 60 and 70 Hz (limits due to motor temperature or maximum current). The compressor may only be operated below the indicated frequency lines (otherwise, select a larger inverter for a wider range of the application limit).to: evaporation temperature, tc: condensing temperature, Δtoh: suction gas superheatDark grey area: mind operating conditions.
Example for application limits for reciprocating compressor 4MTE-10 with refrigerant R744 (CO2) and frequency inverter at 50, 60 and 70 Hz (limits due to motor temperature or maximum current). The compressor may only be operated below the indicated frequency lines (otherwise, select a larger inverter for a wider range of the application limit).
to: evaporation temperature, tc: condensing temperature, Δtoh: suction gas superheat
Dark grey area: mind operating conditions.

Vibrations

Compressor vibrations and pressure pulsations are normally very low by design. However, they can evoke resonance frequencies in piping and heat exchangers (i.e. meet the natural frequency of the system) which result in system sound, vibration, and potentially in piping fatigue and leakage. Possible sources of vibrations are:

The frequency of these vibrations is related to the compressor operating frequency, which can vary over a wide range. Compared to single speed systems (without frequency inverter), this problem is intensified in variable speed applications: Even if the piping is adequate at a given compressor speed, it may not be so at other speeds set by the frequency inverter. For this reason, piping vibrations must be checked throughout the speed range of the compressor, both during the system design development activity and also at commissioning of each individual system (Configuration of the frequency inverter).

Data from sound measurements for each compressor is provided in the Technical Information AT-340 and in the Bitzer Software, tab "Technical data".