When a control command is received at the respective digital input, the motor rotates at ±150
rpm. The same ramp-up and ramp-down times as described above apply.
5.3.3 V/f control or speed control
For induction motors, there are two dierent open-loop control or closed-loop control
techniques:
• V/f control (calculation of the motor voltage using a characteristic curve)
• Closed-loop speed control (also: eld-oriented control or vector control)
Criteria for selecting either V/f control or speed control
In many applications, the V/f control suces to change the speed of induction motors. Examples
of typical applications for V/f control include:
• Pumps
• Fans
• Compressors
• Horizontal conveyors
When compared to V/f control, vector control oers the following advantages:
• The speed is more stable for motor load changes.
• Shorter accelerating times when the setpoint changes.
• Acceleration and braking are possible with an adjustable maximum torque.
• Improved protection of the motor and the driven machine as a result of the adjustable torque
limiting.
• Torque control is only possible with vector control.
Examples of typical applications in which speed control is used:
• Hoisting gear and vertical conveyors
• Winders
• Extruders
It is not permissible to use speed control in the following cases:
• If the motor is too small in comparison to the converter (the rated motor power must not be
less than one quarter of the rated converter power)
• When you operate several motors on one converter
• When the maximum motor speed exceeds the following values:
Commissioning
5.3 Prepare commissioning
Distributed converter for SIMOGEAR geared motors
104 Operating Instructions, 10/2020, FW V4.7 SP13, A5E31298649B AL
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