i950, i750, i700 - Servo control: Parallel operation of asynchronous motors (ASM) possible. Parallel operation of SM theoretically possible, but not practical
Question:
Servo inverter i950, i750 or i700: Can several asynchronous motors (ASM) be connected in parallel and operated in servo control and how must the motor parameters be set for this?
Answer: Yes, it is possible to connect and operate several asynchronous motors (ASM) in parallel in the motor control type 'Servo control ASM' .
When running ASM in parallel, please note the following:
The asynchronous motors must be the same (type, rated data).
The motor shafts must be frictionally coupled to each other, with the same transmission ratio (gearbox, toothed belt,...).
The direction of rotation at the point of frictional coupling must match. With the same setpoint polarity the coupling point must rotate in the same direction. The motor mounting position and the gearbox design must be taken into account in this respect
The motors connected in parallel are recorded by the drive controller as a 'sum motor'.
For the 'summation motor', only the feedback system of one of the motors is connected.
Correspondingly, only one motor temperature sensor (KTY, PT1000) is connected via the feedback line and only the temperature of one motor is evaluated. If the temperature of the other motors is also to be monitored, this must be realized by an external monitoring device .
Recommended procedure for the parameterization:
Use the motor catalog in the engineering tool to select a motor whose motor data corresponds as closely as possible to that of the 'sum motor'. This means that the inverter already presets the corresponding initial values for the controller settings (speed, current) to approximately match
The following nameplate data of the single motor must be entered unchanged:
Engine rated speed (0x2C01:004)
Engine dimensioningfrequency (0x2C01:005)
Motor-Bemessungs-voltage (0x2C01:007)
engine-dimension-cosine-phi (0x2C01:008)
Parameters to be adjusted to the 'sum motor': single motor value multiplied with the number of motors:
Motor rated power (0x2C01:006)
engine-dimensioningcurrent (0x6075)
Motor magnetizing current (0x2C02:003)
Engine rated torque (0x6076)
Engine inertia moment (0x2910:001)
Parameters to be adapted to the 'summation engine': single motor value divided by number of motors:
Motor stator resistance (0x2C01:002)
Motor stator leakage inductance (Lss) (0x2C01:003)
Motor rotor resistance (0x2C02:001)
Motor main inductiveity (Lh) (0x2C02:002)
Parameters, which are to be adapted to the requirements of the application with the 'summation engine':
device: maximum current (0x6073)
Overcurrent monitoring: threshold (0x2D46:001)
Commissioning functions - to be executed after parameterization
'Stromregler-Parameter berechnen' i950/i750: 0x2822:013 = [1], i700: 0x2822 = [4] --> Erforderlich. --> The calculation of the current controller parameters is based on the values previously set for the summator motor. --> Subsequent manual optimization of the current controller settings is only necessary in special cases.
'Feldregler-Parameter berechnen' i950/i750: 0x2822:016 = [1], i700: 0x2822 = [7] --> Optional. --> Eexperience shows that good behavior is achieved even without adaptation .
Notes:
Achievable drive characteristics: The greater the number of asynchronous motors operated in parallel, the greater the effect tolerances of the motor data of the individual motors have on the drive behavior.
Motor load monitoring (i²xt): The settings for the thermal time constants of winding and laminations of a motor are not to be adjusted.
Reference for torque values: The displayed percentage torque values refer to the summation motor, if the torque of the summation motor is entered under Rated torque 0x6076.
Field weakening controller: Since the rated speed does not change due to the parallel connection of the motors,
the field weakening controller does not need to be adjusted either.
Synchronous motors (SM): The parallel operation of SM on an inverter, as described above for ASM, is theoretically possible, but certain conditions must be met, which means that the use is unlikely to be practical in practice. Theoretically, it would be conceivable to couple synchronous motors rigidly and mechanically align the rotors of the motors so that the pole wheel angles match exactly. In this special case, parallel operation of synchronous motors on an inverter is conceivable. The motor data would have to be adapted in the same way as described for ASM
