Once the 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 par. CL-93 PID Proportional Gain and par. CL-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.

2.8.11 Manual PID Adjustment

Start the motor

Set par. CL-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 set-point 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%.

Set par. CL-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 set-point reference to attempt to cause oscillation. Next, increase the PID Integral Time until the feedback signal stabilizes. Then increase

of the Integral Time by 15-50%.

par. CL-95 PID Differentiation Time should only be used for very fast-acting systems. The typical value is 25% of par. CL-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 (par. AN-16, AN-26, E-64 or E-69 as required).

2.9 General Aspects of EMC

2.9.1 General Aspects of EMC Emissions

Electrical interference is usually conducted at frequences in the range 150 kHz to 30 MHz. Airborne interference from the drive system in the range 30 MHz to 1

GHz is generated from the inverter, motor cable, and the motor.

As shown in the illustration below, capacitive currents in the motor cable coupled with a high dV/dt from the motor voltage generate leakage currents.

The use of a screened motor cable increases the leakage current (see illustration below) because screened cables have higher capacitance to earth than

unscreened cables. If the leakage current is not filtered, it will cause greater interference on the mains in the radio frequency range below approximately 5 MHz.

Since the leakage current (I

) is carried back to the unit through the screen (I

motor cable according to the below figure.

The screen reduces the radiated interference but increases the low-frequency interference on the mains. The motor cable screen must be connected to the

frequency converter enclosure as well as on the motor enclosure. This is best done by using integrated screen clamps so as to avoid twisted screen ends (pigtails).

These increase the screen impedance at higher frequencies, which reduces the screen effect and increases the leakage current (I

If a screened cable is used for networknetwork, relay, control cable, signal interface and brake, the screen must be mounted on the enclosure at both ends. In

some situations, however, it will be necessary to break the screen to avoid current loops.

If the screen is to be placed on a mounting plate for the frequency converter, the mounting plate must be made of metal, because the screen currents have to

be conveyed back to the unit. Moreover, ensure good electrical contact from the mounting plate through the mounting screws to the frequency converter chassis.

), there will in principle only be a small electro-magnetic field (I

AF-600 FP Design Guide

) from the screened

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