Tuning the drive to the motor is extremely important.
The purpose is to identify the correct motor flux and stator resistance. This will ensure higher starting torque and better performance especially at low speed operation.
An improperly tuned drive can cause the motor to exhibit instability at low speeds, uneven performance load vs. unloaded through the motors speed range and generate unnecessary faults.
The following AutoTune test need to be performed, when drive is set to Full Vector or Sensorless Vector (not in V/HZ) mode:
Static Tune
A non-rotational test to automatically set the IR Voltage Drop and Ixo Voltage Drop parameters.
Rotate Tune
A rotational test to better identify motor flux and stator electrical properties, which are used to automatically tune the torque/current loop.
Uncouple the motor and do Direction Test before do this.
Here is how to ensure the AutoTune in a PowerFlex drive has been performed correctly:
1. Verify Auto Tune Result Parameters
Flux Current Reference:
This is no load current or magnetizing current. Too low flux in the motor leads to a weaker magnetic field, and cause low torque production.
If too high, it will heat up the motor and more wear over time.
For 4 pole, 20 horsepower (Hp) motors and larger, should be approximately 30% of the motor full load amps.
For 4 pole, 5 horsepower (Hp) motors and smaller, typically the value should be approximately 50% of the motor full load amps
IR Voltage Drop:
Used to compensate the voltage drop across the motor stator resistance.
It’s typically around 2-10% of the motor’s rated voltage (The Voltage value is read @ zero speed)
Ix0 Voltage Drop:
This is the voltage drop across the motor leakage inductance .
Typically value around 25% Motor Nameplate Volt or around 100 volts on 460 Volt Motor.
2. Observe Motor Behavior in Operation
The motor should ramp up & down smoothly without any jerking, overshoot, or pauses.
Can maintain a steady speed and torque without oscillations, especially when holding a constant load
Listen to unusual motor sounds and monitor temperature.
In vector control applications, the motor should produce sufficient torque especially at low speeds
3. Monitor for Drive Alarms or Faults
Overcurrent Alarms: Motor draws excessive current.
Motor Thermal Overload: The motor heats up quickly.
Drive Stability Alarms: Faults related to undervoltage or overvoltage.
Here are the key motor parameters you need to enter correctly, which directly impact the Auto Tune results:
Motor Nameplate Voltage
The rated voltage of the motor.
Motor Nameplate Frequency
The rated frequency of the motor.
Motor Nameplate Full Load Amps
Motor Nameplate RPM
The rated speed of the motor at full load. Don’t enter synchronous RPM here.
Motor Poles
Poles = 120 x (Motor Frequency) / (Synchronous Motor Speed)
Motor Power.
Motor nameplate power rating in KW or HP.
