Start Performance Test; Run Performance Test; Power Circuit Test - Danfoss MCD3000 Series Manual

Tests
The MCD3000 soft starter operation can be verified
using various dynamic test procedures. There is also a
static test procedure that will give accurate information
on the condition of the soft starter. The following
information details the test procedures, test equipment
required and actions to be taken from the test results.

Start Performance Test

This is a dynamic test that verifies the correct
operation of the MCD3000 soft starter during "start
mode". You will need a suitably rated ammeter. Best
results are achieved using a clip on analogue
ammeter. Use the following procedure:
1. Determine the expected start current by
multiplying the programmed Motor Full Load
Current (Parameter 1) by the Current Limit
(Parameter 2).
2. Start the motor and measure the actual start
current.
3. If the expected start current and the measured
start current are the same, the soft starter is
performing correctly.
4. If there is a large variation between the expected
start current and the measured start current, this
could indicate a faulty MCD3000 Main Control
Module or internal Current Transformer. Exchange
the Main Control Module. If the fault remains
check the Current Transformers by measuring the
secondary resistance for continuity and visually
inspecting these circuits.
5. If Current Ramp start mode is used, the minimum
expected start current is the programmed Motor
Full Load Current (Parameter 1) multiplied by the
Initial Current (Parameter 3). Continue with Steps
2 to 4 detailed above.

Run Performance Test

This is a dynamic test that verifies the correct
operation of the MCD3000 soft starter during "run
mode". You will need a suitably rated voltmeter. Use
the following procedure:
1. Ensure that the soft starter is in "run mode". This
can be verified by making sure the "Run" LED
located on the soft starter front display panel is
illuminated.
2. Measure the voltage across each phase of the
soft starter, ie.L1/T1, L2/T2, L3/T3.
3. The measured voltage should be less than 2VAC
when the soft starter is operating correctly. If the
voltage is significantly greater than 2VAC this
could indicate:
• A faulty firing circuit on the Main Control
Module. Exchange the Main Control Module to
see if the fault is removed.
MG.15.B2.02 – VLT is a registered Danfoss trademark
MCD3000 Series
• A faulty SCR gate circuit. With a multimeter,
measure the gate resistance (anode to cathode
/ cathode to anode) of the suspect SCR.
Comparative readings should be taken with a
known healthy SCR device. If the test results
are erroneous, replace the SCR.
• A faulty firing loom circuit. Perform a continuity
test on the firing loom circuit and visually
inspect for a loose connection.

Power Circuit Test

This is a static test that verifies the condition of the
MCD3000 soft starter SCRs, firing looms and Main
Control Module. You will need a 500VDC insulation
tester. A recommended model is the "Megger
BM101/3" or similar. Do not use a hand generated
insulation tester or a standard multimeter (analogue or
digital). These will give erroneous test results. Use the
following procedure:
1. Completely isolate the soft starter so that there
are no main power connections to busbars L1,
L2, L3 and T1, T2, T3. For safety, remove the
control supply power to the soft starter terminals
A1/A2 or A2/A3.
2. Using a suitable insulation tester measure the
resistance across each phase of the soft starter,
ie.L1/T1, L2/T2, L3/T3. These measurements
should also be taken in the reverse direction, ie.
T1/L1, T2/L2, T3/L3.
3. A resistance measurement of 33 to 40kΩ across
each phase indicates a healthy condition. All
readings should be similar.
4. A resistance of less than 10kΩ would indicate that
the SCR power device is suffering from excessive
leakage or a complete short circuit. Replace the
faulty SCR and analyse the system for common
causes of SCR failure (Refer to Section 5.1,
Typical Causes of SCR Damage).
NB!
Damage to an SCR does not necessitate
mandatory replacement of the MCD3000 Main
Control module. Replace of the Main Control module
should be considered only after first having replaced
the damaged SCR(s) and tested the MCD3000 for
correct operation.
5. A resistance of greater than 60kΩ could indicate a
faulty Main Control Module or firing loom.
Exchange the Main Control Module to see if the
fault is removed. If the fault remains, check the
firing loom for continuity and inspect all
connections.
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