Danfoss MCD 202-007-T4-xxx [10/24] N frequently asked questions

Danfoss MCD 201-075-T6-xxx [10/24] N frequently asked questions
MCD 200 Design Guide
Frequently Asked Questions
What is the minimum allowable motor current
when using an MCD 201 open loop soft starter?
There is no minimum current whe n using an
MCD 201 open loop soft starter
What is the minimum allowable motor
current when using an MCD 202 closed
loop soft starter?
The minimum "Motor FLC" se tting is 5 0% of
the MCD 202 nameplate rating. All the motor
protections are based on this setting.
It is possible to operate an MCD 202 with a small kW
motor, for testing purposes. In this case, the m otor
will effectively start DOL, and the MCD 202 will not
protect the motor. T he starter will not trip, because
there is no undercurrent protection on MCD 202.
What type of motor protection does
theMCD202have?
The MCD 202 has built-in motor overload
protection of the electronic "thermal m odel" type.
The motor current is continuously monitored
and the expected temperature is calculated
based on this monitored current.
The rate of rise of the calculated motor temperature
is determined by the Motor Trip Class setting.
The lower this setting, the faster the rate of ris e
of calc u lated motor temperature. An Overcurrent
trip (x 2 Ready LED flashes) will occur when the
calculated temperature reaches 105%. The setting
of the Motor Trip Class pot is similar to a motor trip
class setting on a standard thermal overload relay.
An exter nal motor protection device is not required
when using an MCD 202 soft starter. MCD 202 is
certified to c onform to the IEC60947-4-2 standard
for electronic soft starters. The reliability of the
motor protection feature is part of this standard.
How do I select an MCD 200 soft starter
for duty cycles different from those listed
in the standard ratings table?
The WinStart software package is available for
selecting s oft starters for different duty cycles.
Which MCD 200 models carry the UL mark?
All T6 m odels carry the UL mark.
What are the MCD 200 operational ratings
before maintenance may be required?
The operational ratings for MCD 200 are
size-dependent, and are due to the capability
of the internal bypass relays:
Size 1 & 2 (7.5 ~ 55 kW): 1,000,000 operations
Size 3 (75 ~ 110 kW): 100,000 operations.
When would I use a line contactor?
A line contactor may be compulsory for a specific
installation. This requirement will be the same
whether using a two-phase controlled soft
starter or a three-phase controlled soft starter
(see Product Note for more detail).
How do I size the fuses of the motor
branch circuit (Type 1) when using an
MCD 200 soft starter?
For "Current Limit" s ettings 350% and start times
15 seconds, the nominal rating of standard line
supply fuses (gG) should be 1.75 x Motor FLC.
If motor rated fuses (gM) are being u s ed, their
nominal rating should be 1.5 x M otor FLC.
For "Current Limit" settings > 350% and start
times > 15 seconds, the nominal rating of standard
line supply fuses (gG ) should be 2 x Motor FLC.
If motor rated fuses (gM) are being u s ed, their
nominal rating should be 1.75 x Motor FLC.
When would I use semiconductor fuses?
Either when specified for an installation, or when
Type 2 c oordination is required.
The MCD 200 is internally bypassed, so the SCRs
are in use only during starting and soft stopping.
What is the current consumption of the
MCD 200 control supply?
The steady state consumption of the control supply
is 100 mA maximum, for both CV1 and CV3 models.
However, the short time inrush current at control
supply "switch-on" can be as high as 10 A for
CV3 models, and 2 A for CV1 models (due
to the SMPS power supply).
How can the MCD 202 programmable
output relay be used?
The programmable output relay provides
an N/O contact, which can be used for a
"Trip" or "Run" output.
Trip output:
The relay operates when the MCD 202 trips
on any fault. This can be used to operate a
shunt-trip mechanism of an upstream c ircuit
breaker to isolate the motor branch circuit. It
couldalsobeusedtosignalMCD202"Trip"
status to an automation system.
Run output:
The relay operates on completion of start ramp. This
can be used to operate a contactor for po wer factor
correction capacitors. It could also be used to signal
MCD 202 "Run" status to an automation system.
Is the MCD 202 suitable for flying
start application?
Yes. There is a built-in 2 s econd delay between
the end of one stop and the beginning of the next
start. This delay allows the motor flux to decay,
eliminating any chance of the MCD 202 tripping on
Power Circuit fault (x 1 Ready LED flash) due to
detection of motor bac k EMF when the start signal
is applied. The major effect of a flying start is on
MG.17.C2.02 - VLT is a registered Danfoss trademark
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