- General Electric Computer Accessories User Manual

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• Chapter 3 Paramters/Functions Innovation Series Medium Voltage GP Type - G Drives GEH-6385
System Data Parameters
Exec time/Chop freq
The parameter Exec time/Chop freq defines the Task 1 execution period and the
chopping frequency for the Innovation Series drive product.
Task 1 is the fastest scheduled software process executed within the control.
Primary bridge interface and high-bandwidth aspects of the motor control algorithm
operate in Task 1. Slower tasks execute at integer multiples of the Task 1 interval.
The Task 1 execution period determines the maximum inner regulator bandwidth and
maximum fundamental operating frequency.
The chopping frequency defines the rate at which the power devices may switched
through a full modulation cycle (for example, from the on state, to the off state, and
back to the on state again). The chopping frequency affects the spectral content of
the output waveform, and defines a bridge power de-rating factor which must be
considered in the application of the product.
Chopping frequencies are synchronized to the Task 1 interval such that exactly one
transition or two transitions can be configured to occur per Task 1 period.
Values
The following table describes the available selections for Exec time/Chop freq:
Parameter
Selection
Exec
Time
(usec)
Chop
Freq
(KHz)
Fund
Freq
(Hz)
Power
Derate
(%)
Comments
333 usec, 1.5 KHz 333.3 1.5 200 100 Default
500 usec, 1.0 KHz 500.0 1.0 133 100 Evaluation
only
Motor ctrl alg sel
Parameter Motor ctrl alg sel specifies the presence or absence of a tachometer in the
system and the use of the tachometer in the motor control.
The drive can run the motor using a tachometer-based control scheme, a tachless
control scheme, or a mixture of the two. Tachometer-based control uses speed
feedback from the tachometer to regulate the speed and torque of the motor. Tachless
control provides motor speed and torque regulation without a tachometer. The hybrid
control scheme uses tachometer feedback for speed regulation but not for motor
torque regulation. Greater speed and torque accuracy can be attained when a pulse
tachometer is used with the tachometer-based control.
The following values are available for Motor ctrl alg sel:
• Tachless control: Tachless control of motor speed and torque.
• Tach control and sfb: Tachometer-based control of motor speed and torque.
• Tachles ctl/Tach sfb: Tachometer-based control of motor speed, tachless control
of motor torque.