GE Industrial Solutions AF-600 FP High Power Unit Sizes 6x - Manual (Page 62)

5 Frequency Converter and Motor Applications
5.1 Torque Limit, Current Limit, and Unstable Motor Operation
Excessive loading of the frequency converter may result in warning or tripping on torque limit, overcurrent, or inverter time. This is not a concern if the frequency
converter is properly sized for the application and intermittent load conditions cause anticipated operation in torque limit or an occasional trip. However, nuisance
or unexplained occurrences may be the result of improperly setting specific parameters. The following parameters are important in matching the frequency
converter to the motor for optimum operation. These setting need careful attention.
Par. H-43 Torque Characteristics sets the mode in which the frequency converter will operate.
Parameters P-02 through P-08 match the frequency converter to the motor and adapt to the motor characteristics.
Parameters F-41 and SP-25 set the torque control features of the frequency converter for the application.
Par. H-40 Configuration Mode sets the frequency converter for open or closed loop operation or torque mode operation. In a closed loop configuration, a feedback
signal controls the frequency converter speed. The settings for the PID controller play a key role for stable operation in closed loop, as described in the Operating
Instructions. In open loop, the frequency converter calculates the torque requirement based on current measurements of the motor.
Par. H-43 Torque Characteristics sets the frequency converter for constant or variable torque operation. It is imperative that the correct torque characteristic is
selected, based on the application. If, for example, the load type is constant torque, such as a conveyor, and variable torque is selected, the frequency converter
may have great difficulty starting the load, if started at all. Consult the factory if uncertain about the torque characteristics of an application.
Parameters P-02 through P-07 configure the frequency converter for the connected motor. These are motor power, voltage, frequency, current, and rated motor
speed. Accurate setting of these parameters is very important. Enter the motor data required as listed on the motor nameplate. For effective and efficient load
control, the frequency converter relies on this information for calculating the output waveform in response to the changing demands of the application.
Par. P-04 Auto Tune activates the automatic motor adaptation (auto tune) function. When auto tune is performed, the frequency converter measures the electrical
resistance of the motor stator windings, R1. Since Auto Tune in 6X drives can not calculate R2, X1, X2, and Xm (par. P-31 Rotor Resistance (Rr) to par. P-35 Main
Reactance (Xh)) they must be requested from the motor manufacturer the optimal performance of the drive data. Par. P-31 Rotor Resistance (Rr) and par. P-35 Main
Reactance (Xh), as stated, should be set by the values supplied by the motor manufacturer, or left at the factory default values.
Never adjust these parameters to random values even though it may seem
to improve operation. Such adjustments can result in unpredictable operation
under changing conditions.
Par. F-41 Torque Limiter (Braking) sets the limit for frequency converter torque. The factory setting is 160% for AF-650 GP series and 110% for AF-600 FP series
and will vary with motor power setting. For example, a frequency converter programmed to operate a smaller rated motor will yield a higher torque limit value
than the same frequency converter programmed to operate a larger size motor. It is important that this value not be set too low for the requirements of the
application. In some cases, it may be desirable to have a torque limit set at a lesser value. This offers protection for the application in that the frequency converter
will limit the torque. It may, however, require higher torque at initial start up. Under these circumstances, nuisance tripping may occur.
Par. SP-25 Trip Delay at Torque Limit works in conjunction with torque limit. This parameter selects the length of time the frequency converter operates in torque
limit prior to a trip. The factory default value is off. This means that the frequency converter will not trip on torque limit, but it does not mean it will never trip from
an overload condition. Built into the frequency converter is an internal inverter thermal protection circuit. This circuit monitors the output load on the inverter. If
the load exceeds 100% of the continuous rating of the frequency converter, a timer is activated. If the load remains excessive long enough, the frequency converter
will trip on inverter time. Adjustments cannot be made to alter this circuit. Improper parameter settings effecting load current can result in premature trips of this
type. The timer can be displayed.
High Power Service Manual for Unit Sizes 6x
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