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Motor Characteristics
Listed below are some variable speed AC motor control concepts with which the user of the
GX9 Adjustable Speed Drive should become familiar.
Motor Autotuning
Motor production methods may cause minor differences in the motor operation. The negative effects of
these differences may be minimized by using the Autotune feature of the GX9 ASD. Autotuning is a
function of the GX9 ASD that measures several parameters of the connected motor and places these
readings in a stored table. The software uses the information in the table to help optimize the response of
the GX9 ASD to application-specific load and operational requirements. The Autotuning function may
be enabled for automatic tuning, configured manually, or disabled (see
The measured parameters include the rotor resistance, the stator resistance, the required excitation
inductance, rotational inertia values, and leakage inductance values.
The GX9 ASD is also equipped with a factory-loaded table of motor parameters that fit several different
types of motors. To use this function, disable Autotune and select a motor type at F413.
Pulse Width Modulation Operation
The GX9 ASD uses a sinusoidal Pulse Width Modulation (PWM) control system. The output current
waveform generated by the GX9 ASD approaches that of a perfect sine wave; however, the output
waveform is slightly distorted. For this reason, the motor may produce more heat, noise, and vibration
when operated by a GX9 ASD, rather than directly from commercial power.
Low Speed Operation
Operating a general-purpose motor at lower speeds may cause a decrease in the cooling ability of the
motor. Reducing the torque requirement of the motor at lower speeds will decrease the generated heat at
lower speeds.
When the motor is to be operated at low speed (less than 50% of full speed) and at the rated torque
continuously, a VF motor (designed for use in conjunction with an ASD) is recommended.
Overload Protection Adjustment
The GX9 ASD software monitors the output current of the system and determines when an overload
condition occurs. The overload current level is a percentage of the rated system current. This function
protects the motor from overload.
The default setting for the overload detection circuit is set to the maximum rated current of the GX9 ASD
at the factory. This setting will have to be adjusted to match the rating of the motor with which the GX9
ASD is to be used. To change the overload reference level, see
184.
GX9 ASD Installation and Operation Manual
F400
– F414).
Motor Overload Protection Level 1 on pg.
11
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