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| EN
EIOM v2018.04
3. FANS
Direct-driven centrifugal fans (plug fans) with one of the following motor:
• AC motor;
• EC motor;
• PM motor.
Important:
Electrical connection may only be undertaken by technically trained personnel.
Before making the electrical motor connections, compare the connection specifications with the specifications on the motor identification plate.
Identification plate is attached on the inner side of the motor cover or provided in the technical table on the motor.
Motor thermal protections (if any) must be connected to disconnect the motor from the power supply network in case of motor overheating.
Electric motor must be grounded. Ground terminal or screw is designed for the motor and labeled with “PE” or symbol .
If the fans safety switch is used for connection of the motor, then activation of it must be prevented during service works on the device (by
attaching lock on the handle).
3.1 FANS WITH AC MOTORS (1 SPEED)
Three phase single speed motors can normally be connected for two different voltage ranges (connection in star - higher voltage, or delta - low
-
er voltage).
(1) (2)
Figure 3.1.1 – AC motor (1 speed) wiring diagram for Delta (Δ) and Star (Y) connection.
(1) - Delta (Δ) connection 230V (400V); (2) - Star (Y) connection 400V (690V)
.
Motor starters
Excessive motor temperature due to overloading or failure of one phase can be prevented by using a motor starter. The current at which the starter
trips should be set in accordance with motor nameplate data. In certain cases a standard starter will not give sufficient protection. This applies
to applications with particularly severe duties e.g. starting of loads with high inertia, with the use of inverters, and use in environments with large
changes in ambient temperature. In these cases, winding protection by thermal cut-outs or thermistors should be specified.
Thermal cut-outs
Thermal cut-outs is fitted to the motor winding. When the fixed temperature is exceeded the cut-out will break an electric circuit e.g. to a contactor
which will turn off the motor. The switching contact is a temperature sensitive bimetal spring.
Thermistors
Protection is provided by thermistors fitted in the frame 160 and up motor windings, together with a sensing relay. Thermistors are temperature
sensitive resistors that at a certain temperature have a wide change of resistance. The sensing relay can, in turn, be used to e.g. cut off supply to
the main contactor coil.
Thermal protection contacts of the motor (if any) must be connected using the terminals in the motor junction box.
NOTE: For more information, control, maintenance, diagnostics and troubleshooting refer to AC motors technical specification
Rotation direction
Three-phase motor rotation direction can be changed by switching two of the power supply phases:
(1) (2)
Figure 3.1.2 – Change of rotation for three-phase AC motor:
(1) – clockwise (CW) rotation; (2) – counter clockwise (CCW) rotation;
When frequency converters are used for control of AC motors, shielded cables must be used for connection.
Metal cable glands (EMC) must be used at AC motors connection box.
Before connecting to the motor, cables must be installed through the seals at junction box, which grounds the cable shield part.
