Service manual
6.3.2 Rectifier Circuit Test
Pay close attention to the polarity of the meter leads to
ensure the identification of any faulty component, in case
an incorrect reading appears.
Described next is the procedure to conduct the static test
on the rectifier.
NOTE
In H6 units the +/-UDC terminals are not readily accessible.
Find terminals K601 (+) and K611 (-) between the DC
capacitors.
In H7-H8 units the +/-UDC terminals are directly accessible
on MK900 on the power card.
In I7-I8 units the +/-UDC terminals are accessible on MK900
on the power card or on MK3 on the current sensor board.
For further details, see 6.3.5 Location of UDC Terminals
before measuring)
Rectifier test part I
1. Connect the negative terminal of the multimeter
lead to the positive DC Bus.
2. Connect the positive terminal of the multimeter
lead to the input terminal L1, L2, L3 in turn. The
multimeter indicates Rectifier open.
Rectifier test part II
3. Reverse the meter leads. That is, connect the
positive terminal of the multimeter lead to the
positive DC Bus.
4. Connect the negative terminal of the multimeter
lead to the input terminal L1, L2, L3 in turn. The
multimeter indicates Diode open.
Rectifier test part III
5. Connect the positive terminal of the multimeter
lead to the negative DC Bus.
6. Connect the negative terminal of the multimeter
lead to the input terminal L1, L2, L3 in turn. The
multimeter indicates a diode drop of 0.4 V~0.6 V
(depending on the power size) on the three
terminals.
Rectifier test part IV
7. Reverse the meter leads. That is, connect the
negative terminal of the multimeter lead to the
negative DC Bus.
8. Connect the positive terminal of the multimeter
lead to the input terminal L1, L2, L3 in turn. The
multimeter indicates Diode open.
6.3.3
Inverter Section Tests
The inverter section is primarily made up of the IGBTs used
for switching the DC bus voltage to create the output to
the motor. The frequency converter also has clamping
capacitors between +UDC and -UDC on the IGBT.
CAUTION
Disconnect motor leads when testing inverter section. With
leads connected, a short circuit in one phase reads in all
phases, making isolation difficult.
Before starting tests, ensure that meter is set to diode
scale.
Inverter test part I
1. Connect the positive (+) meter lead to the (+)
positive DC bus terminal.
2. Connect the negative (–) meter lead to terminals
U, V, and W in sequence.
Each reading must show infinity. The meter starts at a low
value and slowly climbs toward infinity due to capacitance
within the frequency converter being charged by the
meter.
Inverter test part II
1. Reverse the meter leads by connecting the
negative (–) meter lead to the positive (+) DC bus
terminal.
2. Connect the positive (+) meter lead to U, V, and
W in sequence. Each reading should show a
diode drop.
Inverter test part III
1. Connect the positive (+) meter lead to the
negative (-) DC bus terminal.
2. Connect the negative (–) meter lead to terminals
U, V, and W in sequence. Each reading should
show a diode drop.
Inverter test part IV
1. Reverse the meter leads by connecting the
negative (–) meter lead to the negative (-) DC bus
terminal.
2. Connect the positive (+) meter lead to U, V, and
W in sequence.
Each reading should show infinity. The meter starts at a
low value and slowly climb toward infinity due to
capacitance within the frequency converter being charged
by the meter.
Test Procedures
VLT
®
HVAC Basic Drive Service Manual
MG90X202 - VLT
®
is a registered Danfoss trademark 49
6
6