Question:
Is it possible to operate two asynchronous motors in parallel on a 9400 HighLine controller in servo control mode? Which parameters must be selected for this?
Answer:
If the corresponding parameters are selected and the below notes are observed, it is possible to operate two asynchronous motors on a 9400 HighLine in servo control mode (C00006/0 = 2):
- Only use identical asynchronous motors.
- If gearboxes are used, the gearbox ratio must be identical.
- There must be a solid connection between both motors.
- The controller detects the two motors connected in parallel as a common motor.
- Only one feedback system is connected to the controller.
- With software version V7.0 and higher, two KTY motor temperature sensors can be evaluated in parallel via the encoder inputs X7 and X8 when using two motors (e. g. twin motor for a storage and retrieval unit or a winder drive). For this, select 'X7 and X8 in parallel' as feedback system for the motor temperature under C01193.
- Temperature switches can be connected in series.
- Basically, PTCs can also be connected in series, however, in this case, the motor temperature monitoring function will probably be actuated slightly earlier due to the addition of the resistance values. As an alternative, you can use an external temperature monitoring for the second motor.
We recommend to proceed as follows with parameter setting:
Select a motor (e. g. from the motor catalogue in the Engineer) with a total power corresponding to the total power of the two motors to load the corresponding standard settings for the control parameters (speed and current controller).
Then, select the following values differing from the motor nameplate data:
- C00081 - rated motor power: double the value
- C00088 - rated motor current: double the value
- C00022 - maximum current: adapt this value as required (double the value).
Select the following values as indicated on the motor nameplate. These values do
not change in case of parallel operation:
- C00087 - rated motor speed
- C00089 - rated motor frequency
- C00090 - rated motor voltage
- C00091 - cos phi of motor
Adapt the following motor parameters compared to the individual motor data:
- C00084 - motor stator resistance: divide value by two
- C00085 - motor stator leakage inductance: divide value by two
For optimising the drive characteristics, if required:
- Determine the inverter error characteristic with C00002 = 71
- Determine the motor parameters with C00002 = 72
After parameter setting, it is useful to check and, if necessary, optimise the current controller settings.
The two motors operated in parallel will be detected as a common motor; the torque display (C00057) also refers to the torque of the common motor.
The settings for the monitoring of the I²t motor utilisation (therminal time constants for coil and plates C00128/1 and 2) do
not change.
Idle state:
At idling speed, there are no problems to be expected with the motor without feedback system when operating two asynchronous motors in parallel, even without a solid connection.
