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6.3.4 Intermediate Section Tests

NOTE

This test is applicable for H7, H8, I7, and I8 units only.

The intermediate section of the frequency converter is

made up of the DC bus capacitors, the DC coils, and the

balance circuit for the capacitors.

1. Test for short circuits with the ohmmeter set on

Rx100 scale or, for a digital meter, select diode.

2. Measure across the positive (+) DC terminal and

the negative (–) DC terminal. Observe the meter

polarity.

3. The meter starts out with low ohms and then

move towards infinity as the meter charges the

capacitors.

4. Reverse meter leads.

5. The meter pegs at zero while the meter

discharges the capacitors. The meter then begins

moving slowly toward two diode drops as the

meter charges the capacitors in the reverse

direction. Although the test does not ensure that

the capacitors are fully functional, it ensures that

no short circuits exist in the intermediate circuit.

Incorrect reading

A short circuit could be caused by a short in the inrush

circuit, rectifier or inverter section. Be sure that the tests

for these circuits have already been performed successfully.

A failure in one of these sections could be read in the

intermediate section since they are all routed via the DC

bus.

The only other likely cause would be a defective capacitor

within the capacitor bank.

There is not an effective test of the capacitor bank when it

is fully assembled. If suspecting a failure within the

capacitor bank, replace the entire bank. Replace the

capacitor bank in accordance with the disassembly

procedures.

6.3.5

Location of UDC Terminals

Remove the IP20 front cover, then remove the capacitor

vibration support. The terminals K601 (+UDC) and K611

(-UDC) are located between the 4 capacitors on the circuit

board. Remove the metal cover to access these terminals.

130BC352.10

Illustration 6.5 UDC Terminals Location on H6 Frequency

Converter

130BC353.10

Illustration 6.6 Metal Cover over Terminals

Test Procedures

VLT

HVAC Basic Drive Service Manual

50 MG90X202 - VLT

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