Danfoss MCD3000 Series, Manual, Page: 52 / 54

MCD3000 Series
52 MG.15.B2.02 – VLT is a registered Danfoss trademark
Appendix
Output Relay Compatibilty
Overview
The MCD3000 soft starter has three programmable
output relays (Output A, B, C). These PCB mount
relays are often used for line or bypass contactor
control.
Recent advances in contactor design have lead to
many manufacturers using electronic contactor coils.
Initially these coils may appear to meet the
specifications of the PCB mount relays. However, in
some instances these electronic contactor coils have a
high initial inrush current due to the internal switch
mode power supply circuitry. This can have a
damaging effect on the PCB mount relays if the
contactor coil is switched directly.
Solution
Before using an MCD3000 soft starter PCB mount
output relay for direct switching of an electronic
contactor coil, consult the contactor
manufacturer/supplier to see if this is advisable.
Certain contactor manufacturers (eg, Klochner
Moellor) state that you cannot use PCB mount relays
for direct switching of their electronic contactor coils.
If this is the case, there are two solutions:
1. Use an MCD3000 soft starter output relay to
control a slave relay. This slave relay can then be
used to directly switch the electronic contactor
coil circuit.
MCD3000
OUTPUT
RELAY
SLAVE
RELAY COIL
K1A
K1A
K1M
CONTACTOR
COIL
A1
A2
2. Some contactor brands have a volt free electronic
input (low voltage/low current). If this is available,
the MCD3000 output relay can be wired directly
into this input for contactor control.
MCD3000
OUTPUT
RELAY
CONTACTOR
COIL
K1M A1
A2
A10
A11