Special voltage motors
If at standard conditions the motor is already running at maximum operating current, a special voltage motor may be useful in order to achieve a larger control range. It ensures that even above supply frequency, a constant voltage-frequency ratio U/f can be maintained. A constant torque is available over the entire application range.
P: max. compressor power consumption
M: max. torque of the motor at compressor shaft
I: max. compressor current consumption
f: frequency (frequency inverter output)
U: voltage (frequency inverter output)
➀: supply frequency / nominal voltage of the motor
Compressor and motor damage in case of exceeding speed!
Observe the upper speed limit of the compressor! See application range.
Depending on design and/or allowed speed range of the compressor, the preferable motor option is (with regard to power supply 400 V/3/50 Hz):
- Motor code 2: 200 V/3/50 Hz at full motor torque – observe maximum allowed speed of the compressor!
①: 400 V/3/50 Hz (motor 4)
②: 200 V/3/50 Hz (motor 2)
With this design, the operating current at graph ② (motor 2) is 1.3 times higher than at graph ① (motor 4). This increases frequency inverter costs resp. the frequency inverter has to be chosen accordingly.