structure
Keypad and
format
Advanced
parameter
descriptions
Serial comms
tuning (see Pr
5.12
{
SE13,
0.34
}).
Pr
4.14
= 1697 x L x f x Imax / V rms
Where :
L is the load inductance in Henries
R is the load resistance in ohms
f is the supply frequency in Hertz
Imax is the peak load current (including any overload) in amps
V rms is the line-to-line supply voltage in volts.
The gain values that are calculated by the autotune system give the best response with minimal overshoot. If required the gains can be adjusted to
improve performance as follows:
1.
The integral gain (Ki) can be used to improve the performance of the current controllers by reducing the effects of
non-linearity. These effects will
be more significant for drives with higher current ratings and higher voltage ratings. If Ki is increased by a factor of 4 it is possible to get up to
10 % overshoot in response to a step change of current reference. For high performance applications, it is recommended that Ki is increased by
a factor of 4 from the autotuned values.
2.
It is possible to increase the proportional gain (Kp) to reduce the response time of the current controllers. If Kp is increased by a factor of 1.5 then
the response to a step change of reference will give 12.5 % overshoot. It is recommended that Ki is increased in preference to Kp.
Pr
4.16
= 1 - Drive current limit is limited to 100 % when estimated motor temperature reaches 100 %.
Pr
4.16
= 2 - Drive trips when estimated motor temperature reaches 100 % and accumulator is reset at power-up.
Pr 4.16 = 3 - Drive current limit is limited to 100 % when estimated motor temperature reaches 100 % and accumulator is reset at power-up.
The motor is modelled thermally in a way that is equivalent to the electrical circuit shown as follows.
2
C
R
Temp
The temperature of the motor as a percentage of maximum temperature, with a constant current magnitude of I, and constant value of motor rated
current (set by Pr
5.07
{
SE07,
0.28
} or Pr
21.07
) after time t is given by
Temp = [I
2
/ (1.05 x Motor rated current)
2
] (1 - e
-t/
) x 100 %
64
Mentor MP Advanced User Guide
www.onxcontrol.com
Issue Number: 4
4.14
Continuous
current
controller
Ki
gain
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