- Designation key
- Operation of fans with frequency converters
Impulse centrifugal fans Centro-Jet are designed for general purpose ventilation of underground and semiopened parkings, smoke extraction in case of fire as a part of smoke extract system.The fans generate a high-speed and high-pressure directed air jet.MODIFICATIONS
Centro-Jet casing is made of polymer coated steel.Due to low height of the casing the fan is recommended for use in low-ceilinged room.The protecting grille on the intake side prevents ingress of foreign objects into the fan.Deflector plates on the exhaust side of the fan ensure correct air flow distribution.
Single- or double-speed 4-, 6- or 8-pole asynchronous motors.Motor ingress protection rating is IP55.The motors are rated for 400 V power mains voltage and 50 Hz frequency.IMPELLER
The impeller with backward curved steel blades.MOUNTING
Centro-Jet fans are designed for ceiling mounting and fixation by means of the supplied fixing brackets.Power is supplied through the internal terminal box.The fan wiring and mounting must be made according to the instructions and the wiring diagram shown in the terminal box.
The fans with the fire resistance rating 200 °C/2 hrs can be manufactured on special request.
|Number of speeds||1||-|
|Voltage||3 ~ 400||V|
|Maximum air flow||6200||m³/h|
|Operating temperature||-25...+55 °С||-|
|Casing material||polymer coated steel||-|
|Model||Fan pull [N]||Pole number||Fire resistance limit/hrs|
|CENTRO-JET: impulse centrifugal fan||–||50N
|–||4 (for single-speed models)
4/6 (for double-speed models)
4/8 (for double-speed models)
|–||_: max. +55 °С
300/2: 300 °С/2 hrs.
400/2: 400 °С/2 hrs.
Ventilation systems produce a heavy load on the electrical systems of a building.DIRECT ON-LINE STARTING (DOL)
As a rule, smoke extraction systems utilize large high-performance fans.During starting the high inertia of the shaft causes a substantial increase in the start-up time – i.e. the time from the application of power to reaching the rated speed.As a result the motor is subjected to high starting current for a prolonged period of time.
Standard switchgear (automatic circuit breakers, contactors and motor starters) is not designed to withstand prolonged overloads causing the fan to shut down automatically during starting. Using switchgear with a higher maximum current rating renders the electric motor protection system less sensitive.As a result the switchgear will not be able to detect motor overload in time due to a higher current sensing threshold.Such challenges can only be addressed by utilizing a soft starter or a frequency converter to start the fan without causing a prolonged overload.
APPLICATIONS IN VENTILATION SYSTEMS
Using an FC or a soft starter allows to reduce the starting current thereby avoiding a loss of voltage in the electrical mains. In addition to that the starting torque and mechanical strain on equipment are also reduced which translates into extended maintenance and repair intervals. General exhaust ventilation (GV) systems and emergency smoke extraction (SE) systems of car parks, warehouses, utility and industrial spaces can be integrated into a single system at the design level. As the air flow rate a GV system is considerably lower than that in an SE system a high-capacity fan rated for smoke extraction duty runs in partial load mode. Frequency converters can be programmed for several fixed-speed settings to enable operation in GV and SE modes. The fan operating modes can be switched upon receiving an external signal from the control system. Such integration of ventilation systems allows overall cost savings.FC-51 AND FC-101: WHEN TO USE?
This catalogue features two series of frequency converters: FC-51 and FC-101. The FC-51 series is only suitable for general ventilation systems. If intended for a smoke extraction system, the fans should be fitted with the FC-101 series units as they feature an integrated fire mode. When activated the integrated protection equipment of the frequency converter is overridden enabling the unit to continue operation despite the possibility of sustaining irreparable damage due to overheating or overloading. In case of a fire, the FC-101 series frequency converters are capable of maintaining a higher air pressure level at landings compared to other areas of the building in order to keep the landings smoke-free.
Therefore, reducing the power consumption is among the top priorities for construction project designers.FREQUENCY CONVERTER
A frequency converter (FC) consists of two main component blocks. One converts alternating current (50 or 60 Hz) into direct current. The other converts direct current into alternating current of variable frequency ranging from 0 to 250 Hz. By controlling the frequency output the FC offers a broad range of motor speed regulation.
During the starting the FC raises the frequency from 0 Hz to the electrical mains frequency (50 or 60 Hz). As the frequency is increased gradually, the motor can be assumed to operate at its nominal speed for a given frequency value. Furthermore, on the assumption that the motor runs at its nominal speed the nominal torque should be immediately available whereas the current will be approximately equal to the nominal value.
Unlike an FC, a soft starter does not change the frequency of speed. Instead it gradually increases the voltage supplied to the motor – from the initial level to the nominal level.
The very low voltage initially supplied to the motor during starting helps avoid sudden jolts. Both voltage and torque increase gradually.
|FREQUENCY CONVERTERS MICRO DRIVE FC-51||FREQUENCY CONVERTERS BASIC DRIVE FC-101|