Toshiba H3 manual Programming Examples contd True Torque Control Programming

TOSHIBA

Programming Examples (cont'd)

True Torque Control Programming

The drive can be programmed to utilize True Torque Control (TTC), the benefits of which are slip compensation and high torque at low speed. In volts per hertz control (or across the line ), a typical AC induction motor will lose 3-5% of its RPM as it goes from no load to full load; when operated in TTC mode, a motor will slow a maximum of 0.5% of base RPM as it is loaded. Motors operated on volts per hertz drives cannot develop their rated torque when operated at low frequencies; the same motor operated in TTC mode can typically develop 200% of its rated torque at one Hz.

The drive divides the motor current it is providing into two components that are ninety degrees out of phase: the excitation current and the torque current. Excitation current is the part of the total current that develops the magnetic field in the motor's core. The torque current is the current that does the useful work. According to the Pythagorean theorem, (total current)2 = (torque current)2 + (excitation current)2. The drive calculates and controls these currents based on motor models to optimize motor performance.

If a Toshiba/Houston motor is used, the drive will use an on-board motor model. If a generic motor is used, the drive can be programmed to auto-tune. During auto tuning, the drive derives a motor model by applying a voltage to the motor and analyzing the resulting decay.

These parameters must be adjusted to use TTC with a TOSHIBA/HOUSTON motor.

Group	Parameter	Value
UTILITY PARAMETERS	BLIND FUNCTION SELECTION	1
UTILITY PARAMETERS	MOTOR PARAMETERS BLIND	1
FUNDAMENTAL PARAMETERS #1	VOLTS PER HERTZ PATTERN	5
MOTOR PARAMETERS	NUMBER OF MOTOR POLES	*
MOTOR PARAMETERS	MOTOR RATED CAPACITY	*
MOTOR PARAMETERS	MOTOR TYPE	**
MOTOR PARAMETERS	LOAD MOMENT OF INERTIA	***

The following parameters must be adjusted to use TTC for a GENERIC motor.

Group	Parameter	Value
UTILITY PARAMETERS	BLIND FUNCTION SELECTION	1
UTILITY PARAMETERS	MOTOR PARAMETERS BLIND	1
FUNDAMENTAL PARAMETERS #1	VOLTS PER HERTZ PATTERN	5
MOTOR PARAMETERS	NUMBER OF MOTOR POLES	*
MOTOR PARAMETERS	MOTOR RATED CAPACITY	*
MOTOR PARAMETERS	MOTOR TYPE	2
MOTOR PARAMETERS	MOTOR RATED VOLTAGE	*
MOTOR PARAMETERS	MOTOR RATED FREQUENCY	*
MOTOR PARAMETERS	MOTOR RATED RPM	*
MOTOR PARAMETERS	AUTO-TUNING ENABLE	1****
MOTOR PARAMETERS	LOAD MOMENT OF INERTIA	***

*Enter appropriate value from motor's nameplate. KW = 0.746 X HP. ** Enter "0" for an EQPIII or "1" for a high efficiency motor.

*** If the drive displays AUTO TUNE ERROR, try a different inertia setting.

**** The drive will auto tune the next time a run is initiated. This parameter is then reset to "0" by the drive`.

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