7 | Electrical Installation
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Operating instructions CMVpro 125-400 | Version 1-en
• provides qualified personnel a means of directly controlling and disconnect-
ing the electrical power supply from the fan,
• shall therefore be executed as a lockable all-pole disconnect switch.
7.2.2
Motor protection switch installation
An electric motor with a nominal power rating over 0.5 kW is to be protected
against overheating and connected to the electrical power supply with a motor
protection device (overload and short circuit protection) suitable for this.
NOTICE
Risk of overheating of the electric motor
Damage to motor
The motor protection switch does not reliably protect the electric motor from
overheating, particularly with insufficient motor cooling due to low speed, defec-
tive fan impeller, or clogged ventilation grid.
u
The installation of a motor protection switch is the responsibility of the oper-
ator.
u
Specify the motor protection switch based on the motor rated current on the
nameplate.
If a frequency converter (FC) is used, clarify whether integrated motor protection
functions allow for fan operation without an additional motor protection switch.
The FC is to be parameterized with the motor data by qualified personnel.
7.2.3
Starting current limiter
NOTICE
Strong mechanical load by the fan.
Thermal and electrodynamic load on the motor windings.
Reduced service life of the fan.
Disturbance of nearby electrical equipment, such as controllers.
▪ When larger fans are switched on and ramped up under full mains voltage,
a high inrush current is generated.
▪ When the fan is started directly, excessive torque occurs that can severely
stress and damage the impeller and motor bearings.
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The manufacturer recommends the use of a starting current limiter starting
with motor ratings of 3 kW (e.g. star-delta starter, soft starter, or soft start
with frequency converter (FC)).
At the latest, for fans with a motor rating above 4 kW, the starting current is to
be limited by one of the listed methods or equipment:
• Star-delta start-up
• Soft start/soft starter
• FC with current-limiting and start-up characteristics.
Observe the national regulations and limit values of the power system operator
for direct start-up of three-phase motors.