User's Manual

Geo MACRO Drive User Manual
96 Setting Up Turbo Motor Operation
Setting I
2
T Protection
It is important to set the I
2
T protection for the amplifier/motor system for Turbo PMAC2 direct PWM
commutation. Normally, an amplifier has internal I
2
T protection because it is closing the current loop.
When Turbo PMAC2 is closing the current loop, the amplifier cannot protect itself or the motor from over
heating. Either set up the I
2
T protection using one of the Setup Programs or set the Ixx69, Ixx57 and
Ixx58 variables manually based on the following specifications:
Parameter Description Notes
MAX ADC Value Maximum Current output of amplifier
relative to a value of 32767 in Ixx69
GMx012xx = 7.3 A Peak
GMx032xx = 14.6A Peak
GMx05xxx = 16.3A Peak
GMx10xxx = 32.5A Peak
GMx15xxx = 48.8A Peak
GMx201xx = 65 A Peak
GMx301xx = 97.6A Peak
x = Position in part number is
irrelevant.
Instantaneous Current Limit The lower of the amplifier or motor system RMS or Peak*
Continuous Current Limit The lower of the amplifier or motor system Usually RMS
I
2
T protection time Time at instantaneous limit Two seconds
Magnetization Current Ixx77 value for induction motors Only for induction motors
Servo Update Frequency Default is 2258 Hz.
* If specification given in RMS, multiply with x1.41 to obtain peak current for calculations.
Example Calculations for Direct PWM commutated motor:
MAX ADC = 32.5A
Instantaneous Current Limit = 10A Peak
Continuous Current Limit = 5A RMS
I
2
T protection time = 2 seconds
Magnetization Current (Ixx77) = 0
Servo Update = 2.258 kHz
)30(32767
)(tantan
69 °= xCosx
ADCMAX
PeakLimiteoussIn
Ixx
if calculated Ix69 >32767, then Ixx69 should be set equal to 32767
69
tantan
57 xIxx
LimiteoussIn
LimitContinuous
Ixx =
)(sec)(
2
32768
2
57
2
77
2
69
58 ondsimePermittedTHzeRateServoUpdat
IxxIxx Ixx
Ixx ××
−+
=
Based on the above data and equations, the following results:
Ixx69= 8731
Ixx57=4366
Ixx58=240
For details about I
2
T protection, refer to the safety sections of the User Manual. Details about the variable
setup can be found in the Software Reference manual.