Soft Charge And Rectifier Circuits Test: E-Frame Size - Danfoss VLT HVAC Drive FC 100 Service Manual

High Power Service Manual for VLT
Adjustable Frequency Drives

6.2.3 Soft Charge and Rectifier Circuits Test: E-frame Size

For E-frame size adjustable frequency drives, the rectifier and soft charge circuits are tested sep-
arately. The soft charge circuit is made up of the soft charge rectifier, fuses and the soft charge
resistor. The rectifier circuit is made up of the SCR and diode modules. The soft charge resistor
limits the inrush current when power is applied to the adjustable frequency drive. The soft charge
circuit card also provides snubbing for the SCRs.
It is important to pay close attention to the polarity of the meter leads to ensure identification of
a faulty component should an incorrect reading appear.
Prior to performing the test, it is necessary to ensure the soft charge fuses, F1, F2, and F3, located
on the soft charge card, are good. An open fuse could indicate a problem in the soft charge circuit.
Continue test procedures.
Figure 6-6 shows the soft charge card and the location of the fuses. It is for reference only. It is
not necessary to remove the card to perform the tests.
Disconnect the MK3 from the soft charge card and leave disconnected until completion of soft
charge and rectifier tests.
Soft charge fuse test
Use a digital ohmmeter to test continuity on rectifier fuses F1, F2, and F3 on the soft
charge card.
1. Measure F1 across fuse. Open reading indicates open (blown) fuse.
2. Measure F2 across fuse. Open reading indicates open (blown) fuse.
3. Measure F3 across fuse. Open reading indicates open (blown) fuse.
A measurement of 0 ohms indicates good continuity. Replace any open fuse (infinite resistance).
Figure 6.8: Soft Charge Card Fuse Location
380–480/500V: Blue MOV and 8 PTCs.
1 Fuses F1, F2 and F3
®
FC Series
2
1
2
MG.90.L1.22 - VLT ® is a registered Danfoss trademark
525–690 V: Red MOV and 6 PTCs.
MK3 (disconnect for soft charge and rectifier tests)
6 Test Procedures
6
6-9