Danfoss VLT 5000-P User Manual

5-4
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5.1.1.2 Main Rectifier Circuit Test Part I
1. Connect positive (+) meter lead to positive (+)
DC bus connector MK105 (A) on power card.
2. Connect negative (–) meter lead to terminals L1,
L2, and L3 in turn.
Each reading should show infinity. The meter will start at a low
value and slowly climb towards infinity due to capacitance within
the drive being charged by the meter.
Incorrect Reading
With the Part I test connection, the SCRs in the SCR/Diode
modules are reverse biased so they are blocking current flow.
If a short circuit exists, it would be possible that either the
SCRs or the diodes in the soft charge rectifier are shorted. To
isolate between SCRs or the soft charge rectifier, perform the
Soft Charge Rectifier Test.
5.1.1.3 Main Rectifier Circuit Test Part II
1. Reverse meter leads by connecting negative (–)
meter lead to positive (+) DC bus connector
MK105 (A) on power card.
2. Connect positive (+) meter lead to L1, L2, and
L3 in turn. Each reading should show a diode
drop.
Incorrect Reading
With the Part II test connection, even though the SCRs in the
SCR/Diode modules are forward biased by the meter, current
will not flow through the SCRs without providing a signal to
their gates. The upper diodes in the soft charge rectifier are
forward biased so the meter reads the voltage drop across
those diodes.
If an open reading were present, it would indicate the upper
diodes in the soft charge rectifier are open. It could also indicate
that one or more of the soft charge fuses are open. It could
further indicate that the soft charge resistor is open. To isolate
between the three possibilities, perform the Soft Charge Fuse
Test and Soft Charge Rectifier Test.
A short circuit reading indicates either one or more of the upper
soft charge rectifier diodes are shorted or the SCRs are shorted
in the SCR/Diode module. To isolate between SCRs or the
soft charge rectifier, perform the Soft Charge Rectifier Test.
5.1.1.4 Main Rectifier Circuit Test Part III
1. Connect positive (+) meter lead to negative (-)
DC bus connector MK105 (B) on power card.
2. Connect negative (–) meter lead to terminals L1,
L2 and L3 in turn. Each reading should show a
diode drop.
Incorrect Reading
With the Part III test connection, the diodes in the SCR/Diode
modules are forward biased as well as the lower diodes in the
soft charge rectifier. The meter reads the diode drops. If a
short circuit exists it would be possible that either the diodes in
the SCR/Diode modules or the lower diodes in the soft charge
rectifier are shorted. To isolate between SCRs or the soft charge
rectifier, perform the Soft Charge Rectifier Test.
Although an open reading is possible, it is unlikely since that
indicates that both the diodes in the SCR/diode modules and
the lower diodes in the soft charge rectifier are open. Should
that occur, replace both diodes.
5.1.1.5 Main Rectifier Circuit Test Part IV
1. Reverse meter leads by connecting negative (–)
meter lead to negative (-) DC bus connector
MK105 (B) on power card.
2. Connect positive (+) meter lead to L1, L2 and L3
in turn. Each reading should show infinity.
Each reading should show infinity. The meter will start at a low
value and slowly climb toward infinity due to capacitance within
the drive being charged by the meter.
Incorrect Reading
With the Part IV test connection, the diodes in the SCR/Diode
modules are reversed biased as well as the lower diodes in
the soft charge rectifier. If a short circuit exists it would be
possible that either the diodes in the SCR/Diode modules or
the lower diodes in the soft charge rectifier are shorted. To
isolate between SCRs or the soft charge rectifier, perform the
Soft Charge Rectifier Test, 5.1.2.

Danfoss VLT 5000-P Specifications

General

Brand	Danfoss
Model	VLT 5000-P
Category	DC Drives
Language	English