WEG ECW500, User Manual

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Functional Description .
ECW500 | 51
The protections in general do not turn off the excitation, they only serve as a fault warning. On the other hand,
some protections may be configured by the user to perform certain actions, such as turning off the excitation or
switch to the MECC mode.
All protections can be enabled/disabled individually. In order to configure the relays to inform the protections,
refer to section 6.9.3 Configurable Relays 0, 1, 2 and 3.
6.7.1 Feedback Loss Protection (PFL)
The feedback loss protection actuates whenever the ECW500 detects problems in the feedback voltages. Two
situations can cause this fault:
■ The three phases of the machine fall below the balance level set for a period longer than the time set for the
protection to actuate.
■
If any of the three phases is different from the average of the three phases by a value greater than the
unbalance level set for a period longer than the setting of this protection.
The configuration of this protection has five parameters:
■ enable/disable the protection (30286);
■ a parameter that allows configuring the switch to the MECC mode in case of fault (30288);
■ the balance level (30292);
■ the unbalance level (30294) and
■
the time for the protection to actuate (30290).
6.7.2 Excitation Overvoltage Protection (PEOV)
The protection actuates whenever the excitation voltage exceeds the level configured by a time set. Three
parameters are available to set this protection: enable/disable (30422), the overvoltage level (30424) and time for
the protection to actuate (30426).
6.7.3 Fault Protection in the Rotating Diodes (PED)
The ECW500 monitors the operation of the rotating diodes of the exciter without brushes through the analysis of
the excitation current and protects against short circuit and open circuit of these semiconductors.
To perform this function, the ECW500 monitors in real time the harmonic content of the wave form of the
excitation current through the Fast Fourier Transform (FFT). Six parameters are available for configuration of the
protection:
▪ enable/disable (30466);
▪ a parameter that indicates whether the ECW500 must shut down in case of fault (30470);
▪
the time for the protection to actuate (30468);
▪ the ripple level of the excitation current detected by the maximum and minimum excitation current
measured (30464);
▪
the maximum levels allowed for the first harmonic (30460) and
▪ the maximum levels allowed for the second harmonic (30462).
To adjust correctly this protection, follow the steps below:
1. Excite the synchronous machine and check the average levels measured for the ripple current
excitation (40092)
amplitude (40086) nics (40088).
2. Adjust the parameter of maximum ripple (30464) 10 to 15 % above the average level checked in the
normal condition.
3. Adjust the first (30460) harmonics limits (30462) 1 to 2 % above of the average levels
checked in the normal condition.
4. Program a delay time (30468) above of 30 s, to avoid the undue actuation of protection.