Danfoss VLT HVAC Drive FC 100 Series, Руководство по конструкции

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2.8.11 Tuning the Drive Closed-loop Controller
Once the adjustable frequency drive's closed-loop controller has been set up, the performance of the controller should be
tested. In many cases, its performance may be acceptable using the default values of
20-93 PID Proportional Gain and
20-94 PID Integral Time . However, in some cases it may be helpful to optimize these parameter values to provide faster
system response while still controlling speed overshoot.
2.8.12 Manual PID Adjustment
1. Start the motor
2. Set 20-93 PID Proportional Gain to 0.3 and increase it until the feedback signal begins to oscillate. If necessary, start
and stop the drive or make step changes in the setpoint reference to attempt to cause oscillation. Next reduce the
PID Proportional Gain until the feedback signal stabilizes. Then reduce the proportional gain by 40-60%.
3. Set 20-94 PID Integral Time to 20 sec. and reduce it until the feedback signal begins to oscillate. If necessary, start
and stop the drive or make step changes in the setpoint reference to attempt to cause oscillation. Next, increase
the PID Integral Time until the feedback signal stabilizes. Then increase the Integral Time by 15–50%.
4. 20-95 PID Differentiation Time should only be used for very fast-acting systems. The typical value is 25% of
20-94 PID Integral Time . The differential function should only be used when the setting of the proportional gain
and the integral time has been fully optimized. Make sure that oscillations of the feedback signal are sufficiently
dampened by the low-pass filter for the feedback signal (parameters 6-16, 6-26, 5-54 or 5-59 as required).
2.9 General aspects of EMC
2.9.1 General Aspects of EMC Emissions
Electrical interference is usually conducted at frequencies in the range 150 kHz to 30 MHz. Airborne interference from the
Adjustable frequency drive system in the range 30 MHz to 1 GHz is generated from the inverter, motor cable, and the
motor.
As shown in
Figure 2.30 , capacitive currents in the motor cable coupled with a high dU/dt from the motor voltage generate
leakage currents.
The use of a shielded motor cable increases the leakage current (see
Figure 2.30 ) because shielded cables have higher
capacitance to ground than non-shielded cables. If the leakage current is not filtered, it will cause greater interference on
the line power in the radio frequency range below approximately 5 MHz. Since the leakage current (I
1
) is carried back to the
unit through the shield (I
3
), there will in principle only be a small electro-magnetic field (I
4
) from the shielded motor cable
according to the below figure.
The shield reduces the radiated interference, but increases the low-frequency interference in the line power supply. The
motor cable shield must be connected to the Adjustable frequency drive enclosure as well as on the motor enclosure. This
is best done by using integrated shield clamps so as to avoid twisted shield ends (pigtails). These increase the shield
impedance at higher frequencies, which reduces the shield effect and increases the leakage current (I
4
).
If a shielded cable is used for serial communication bus, relay, control cable, signal interface and brake, the shield must be
mounted on the enclosure at both ends. In some situations, however, it will be necessary to break the shield to avoid
current loops.
Introduction to VLT® HVAC D...
VLT
®
HVAC Drive Design Guide
2-32 MG11BB22 - VLT
®
is a registered Danfoss trademark
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