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DSD 412 Input Fuse Blowing

September 2002

A problem seen now and then is Input Fuse blowing (F1, F2, F3) during deceleration. Usually occurs when the DSD 412 is first being set up. It can also be caused by low AC line voltage which we will also discuss.

Here are some tips on how to correct this:

  1. DSD 412 Drives using Gen-Ele-2/CS0386 software(U13/U14 - 97SA3860-0010/97SA3861-0010) have automatic calculation of the Full Field/Weak Field crossover point. (skip to step #6)

  2. Refer to page 56 of the DSD 412 Technical Manual (CS 0274, rev 02). Figure 4.1 shows the Field Regulator Set-Up Adjustments.

  3. Ensure that the DSD 412 Field Control is working properly by;
    - Verify Field Current with clamp-on DC Ammeter, or
    - Measure VDC output to motor field
    - Verifying settings for Rated Field Voltage (F#52), Field VAC (F#55), and Field Response (F#54). These settings affect Stability and Response of the DSD 412 Motor Field Control. If not set correctly, can cause sluggish response or instability, with CEMF over voltage, etc.

  4. Note that F#49, Weak Field Current, controls the steady state Motor CEMF. Adjust F#49 to yield correct CEMF (F#609) while running at constant top speed. (CEMF should not exceed Armature Motor Voltage (F#610)

  5. Monitor the CEMF voltage at F#609 as the elevator starts the Decel portion of the Motor Speed Profile. If the CEMF is too high, you will get F407 DCU CEMF Faults (check the F#800 Log). If you get F408 PCU CEMF Faults, the Drive will shutdown. To lower the CEMF voltage, lower the value entered in F#56, Field Strength Speed. This will lower the point on the Motor Speed Profile at which the Field Current begins to strengthen to Full Field. Figure 4.1 in the CS 0274 Tech Manual shows this point.

  6. Low AC Line - A dip in the AC Input Line Voltage can also cause CEMF problems. If the AC Line drops too low during DSD 412 bridge reversal, the SCR's that should turn off due to AC Line Voltage Commutation will not, and Input Fuses will be blown. Try a higher voltage tap on the isolation transformer secondary.
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