Abstract: A drive device for a rotary electric machine includes a first inverter that has high-potential side and low-potential side switching elements corresponding to phases of the rotary electric machine and is connected to a DC power supply, a second inverter that has high-potential side and low-potential side switching elements corresponding to the phases and is connected to the first inverter via a connection line, and a controller that controls the first and second inverters so that if a percentage modulation expressed by a fundamental wave component amplitude of a phase winding voltage and a DC voltage is a threshold value or more, percentage modulations of output phase voltages of the first and second inverters are more than 1, and so that a phase difference between a phase of the output phase voltage of the first inverter section and that of the second inverter section changes depending on the percentage modulation.

Abstract: A motor assembly for use with a power tool includes a motor housing, a brushless electric motor disposed at least partially in the motor housing, and a PCB assembly coupled to the motor housing. The PCB assembly includes a heat sink, a power PCB coupled to a first side of the heat sink, and a position sensor PCB coupled to a second side of the heat sink opposite the first side and in facing relationship with the motor.

Abstract: A failure detection frequency of failure diagnosis for a cut-off function can be improved. An on-vehicle control device includes a microcomputer that performs a control operation of an external device, a monitoring element that monitors the microcomputer, an output drive circuit that sends a control signal to the external device based on an instruction from the microcomputer, a communication circuit that switches a communication state with another on-vehicle control device based on an instruction from the monitoring element, and an energization cut-off element that energizes and cuts off a power supply voltage to be supplied to the output drive circuit based on an instruction from the monitoring element. The monitoring element independently instructs the switching of the communication state by the communication circuit and the energization and cut-off of the power supply voltage by the energization cut-off element.

Abstract: A dual-rotor in-wheel motor based on an axial magnetic field and a control method thereof are provided. The dual-rotor in-wheel motor includes an axle and a hub. The axle is fixedly connected to a frame. The hub relatively rotates around the axle. A disc-shaped intermediate stator is fixedly connected on the axle. A left coil assembly and a right coil assembly are fixedly mounted on two sides of the intermediate stator, respectively. A left rotor and a right rotor are respectively arranged on the two sides of the intermediate stator. The left coil assembly drives the left rotor to rotate, and the right coil assembly drives the right rotor to rotate. A left clutch is arranged between the left rotor and the hub, and a right clutch and a speed reduction mechanism are arranged between the right rotor and the hub.

Abstract: A rotational motor includes a stator and a rotor and at least two magnets including a permanent magnet and an electromagnet, wherein one of the magnets is attached to the stator and one of the magnets is attached to the rotor. The magnets are relatively aligned such that when the electromagnet is switched off, the permanent magnet is attracted to a ferromagnetic core of the electromagnet causing the rotor to rotate relative to the stator, and when the electromagnet is switched on, the permanent magnet is repelled from the electromagnet causing the rotor to continue to rotate relative to the stator.

Abstract: A control apparatus is provided for controlling drive of a rotating electric machine that has coils of two or more phases. The control apparatus includes a first inverter to be connected with first ends of the coils, a second inverter to be connected with second ends of the coils, and a controller. The first inverter has a plurality of first switching elements each corresponding to one of the coils. The second inverter has a plurality of second switching elements each corresponding to one of the coils. The controller includes a first operation circuit configured to generate a first control signal for control of the first inverter and a second operation circuit configured to generate a second control signal for control of the second inverter. Moreover, the control apparatus is configured so that switching timings are synchronized, based on synchronization information, between the first and second inverters.

Abstract: The invention includes a first power supply connector, which connects a first inverter unit that supplies a drive current to a first three-phase winding of a rotary electric machine to a first vehicle power supply, and a second power supply connector, which connects a first second inverter unit that supplies a drive current to a second three-phase winding of the rotary electric machine to a second vehicle power supply, wherein a voltage of the first vehicle power supply is higher than a voltage of the second vehicle power supply, and a current capacity of the first power supply connector is smaller than a current capacity of the second power supply connector.

Abstract: An electric power conversion device includes: a first electric power conversion circuit, a current detection circuit, an electric power conversion circuit of field coil excite use, a control circuit, and detector which detects an induced electromotive force generated in the motor generator. In a case where an over current, is detected by the first electric power conversion circuit, the control circuit turns off a switching of a phase of the first electric power conversion circuit from which an over current s detected and a switching of the electric power conversion circuit of field coil excite use. After the value of an induced electromotive force by the motor generator falls below a predetermined value, the control circuit controls to stop a supply of electric power of all phases by the first electric power conversion circuit.

Abstract: The present invention provides a fan motor which includes a housing, a stator disposed inside the housing, a rotor disposed inside the stator, a blade coupled to the rotor and a printed circuit board disposed under the blade, wherein the housing includes an upper housing and a lower housing, wherein a board coupling portion to which the printed circuit board is coupled is disposed concavely formed at a lower outer surface of the lower housing, and the first mounting portion of the printed circuit board is coupled to the board coupling portion, wherein the board coupling portion includes a component hole and the component hole is disposed between an outer circumferential surface of the blade and an inner circumferential surface thereof. Therefore, an advantageous effect that a component having a large height may be mounted within a limited design height.

Abstract: An optical element driving mechanism is provided. The optical element driving mechanism includes a fixed portion, a movable portion, and a driving assembly. The movable portion is movably disposed on the fixed portion. The driving assembly is disposed on the fixed portion and drives the movable portion to move relative to the fixed portion.

Abstract: A rotor for a machine has a plurality of rotor segments, each rotor segment forming at least one rotor pole and having a plurality of permanent magnets interior to the rotor and at least one saturatable bridge section for each permanent magnet in the rotor segment, each saturatable bridge section comprising a protrusion between air regions separating a north pole and a south pole of the permanent magnet to cause a portion of magnetic flux from the permanent magnet to traverse the saturatable bridge and cause a majority of the permanent magnet flux through an air gap of a rotor-stator interface between the rotor and a stator of the machine and through a stator pole.

Abstract: Embodiments of a direct-drive fan system and a variable process control system are disclosed herein. The direct-drive fan system and the variable process control system efficiently manage the operation of fans in a cooling system such as a wet-cooling tower or air-cooled heat exchanger (ACHE), HVAC systems, mechanical towers or chiller systems.

Abstract: An electric motor may comprise a rotor and a stator comprising rotor and stator teeth, respectively. A non-uniform angular spacing or grouping of rotor teeth may facilitate desired rotational speeds of the rotor.

Abstract: A motor control device drives a motor provided as a drive source of an electric actuator by performing vector control using d-q rotational coordinates, and sets a d-axis current command value so as to weaken field flux of the motor when torque is applied to the motor from the exterior in a direction that is the same as a rotation direction of the motor. When the rotational speed of the motor exceeds the predetermined upper rotational speed limit, the motor control device calculates a correction amount of the d-axis current command value so as to make a rotational speed of the motor converge to a predetermined upper rotational speed limit, and corrects the d-axis current command value by this correction amount.

Abstract: Two systems of individually-provided arithmetic units in a control device of a multi-phase rotating machine perform control calculation for a control of electric current flowing from power converters to the multi-phase windings. The arithmetic units of the respective systems communicate information via inter-system communication at least in one direction, and perform current control calculation of the electric current flowing in the multi-phase windings of a subject system in a cycle shorter than a communication cycle of the inter-system communication, and calculate a decoupling control amount of the electric current flowing in the multi-phase windings of the subject system, for a decoupling control of a voltage generated in the multi-phase windings of the subject system by the electric current flowing in the multi-phase windings of an other system by using an estimated current that is calculated based on a current instruction value of the subject system or of the other system.

Abstract: A motor includes a first inverter connected to one end of a winding of each phase and a second inverter connected to another end of the winding of each phase. The first inverter includes a terminal electrically connected to one end of a U-phase winding. The second inverter includes a terminal electrically connected to another end of the U-phase winding. Current output from the terminal of the first inverter and passing through the U-phase winding flows to the terminal of the second inverter. Current output from the terminal of the second inverter and passing through the U-phase winding flows to the terminal of the first inverter. The terminal of the first inverter and the terminal of the second inverter are adjacent to each other.

Abstract: At least one of conditions are satisfied, the conditions are a condition that directions of vectors of N sets of first pulse voltages are different from each other, a condition that directions of vectors of N sets of second pulse voltages are different from each other, and a condition that directions of vectors of N sets of third pulse voltages are different from each other. Further, periods in which voltages having different directions of the vectors among the N sets of the first, the second and the third pulse voltages, are applied at least partially overlap with each other.

Abstract: There is provided a drive device configured to impose a more appropriate limitation on driving of a motor. The drive device comprises a motor configured to generate an induced voltage according to a rotation speed, and an inverter configured to drive the motor. Upon satisfaction of a predetermined condition to impose a limitation on driving of the motor, the drive device performs a drive limitation that imposes a larger limitation on driving of the motor when the induced voltage of the motor is higher than an input voltage that is input from a power storage device side to the inverter, compared with a limitation imposed when the induced voltage of the motor is equal to or lower than the input voltage.

Abstract: A motor vehicle control system (210C, 220) for controlling an electric propulsion motor (230) to drive a wheel (290) of the vehicle (200), the control system (210C, 220) being configured to operate in one of a first mode and a second mode in dependence at least in part on an amount of slip experienced by at least one driven wheel (290), in the first mode the control system (210C, 220) being configured to cause the at least one electric propulsion motor (230) to generate a predetermined amount of drive torque, in the second mode the control system (210C, 220) being configured to cause the at least one electric propulsion motor (230) to rotate at a predetermined speed, wherein the control system (210C, 220) is configured to operate in the first mode if the amount of slip experienced by the at least one driven wheel (290) is below a predetermined slip amount and to operate in the second mode if the amount of slip experienced by the at least one driven wheel (290) exceeds the predetermined slip amount.

Abstract: An electric machine is provided which includes a rotor disk extending along a radial direction and having a rotor flange attached to or formed integrally with the rotor disk and extending substantially along the axial direction. A plurality of rotor magnets are mounted on the rotor disk and supported by the rotor flange such that the rotor flange absorbs centrifugal loads exerted on the magnets and enables high speeds of operation.

Abstract: A brushless DC dynamo includes a circular armature with N sets of first armature coils spaced with each other in sequence, N sets of second armature coils spaced with each other in sequence, a plurality of first wires and a plurality of second wires, and each first wire and each second wire respectively interconnecting between one set of the first armature coils and one set of the second armature coils; a control unit; a magnetic unit, disposed inside the circular armature unit, comprising a pair of magnetic poles, wherein the circular armature unit and the magnetic unit can rotate relatively to each other under control; and a position sensor for detecting the position of the magnetic unit, and outputting the information of magnetic unit's position to the control unit to trigger the control unit to output a control signal to control the first and second control switches.

Abstract: A motor system according to the present invention includes: a motor including a first winding portion and a second winding portion, the second winding portion having a larger number of turns than the first winding portion; a first inverter connected to the first winding portion; and a second inverter connected to the second winding portion.

Abstract: Provided is a motor driving apparatus used for driving a motor including a first winding group and a second winding group to which three-phase alternating-current voltages are applied. The motor driving apparatus includes a first inverter and a second inverter; the first inverter applies an alternating-current voltage to the first winding group; and the second inverter applies an alternating-current voltage to the second winding group. A first induced voltage detector, a second induced voltage detector, and a third induced voltage detector are provided as voltage detectors for detecting induced voltages induced either in the first winding group or in the second winding group.

Abstract: An automatically variable torque and speed motor for electrical tricycles is disclosed, and the motor rotor assembly of which comprises fixed rotors and rotary rotors arranged adjacently in turn along the axis of the motor shaft. Staggered pole pieces on the surfaces of the fixed rotor and the rotary rotor form a staggered angle ? along the circumference. The support of the rotary rotor comprises a revolving support ring and two fixed side discs which are respectively arranged on the two sides of the revolving support ring. An elastic compression part is arranged in the inner cavity of the revolving support ring along the revolving direction. The elastic compression part has one end arranged at the inner circle of the revolving support ring and the other end arranged on the side wall, facing the inner cavity of the revolving support ring, of one of the fixed side discs. The present invention can adjust the speed and torque according to the load situations of the whole electrical tricycle.

Abstract: According to an aspect, an elevator system includes an elevator car 14 to travel in a hoistway 11 and a linear propulsion system 20 to impart force to the elevator car. The linear propulsion system includes a secondary portion 18 mounted to the elevator car and a primary portion 16 mounted in the hoistway. The primary portion includes a plurality of motor segments 26. The elevator system also includes a load sensor 52 operable to detect an elevator load on a brake. The elevator system further includes a control system 46 operable to apply an electrical current to at least one of the motor segments that overlaps the secondary portion, determine a measurement of the elevator load, and vary an electrical angle estimate while the brake is engaged and thrust is applied.

Abstract: A motor device includes a first stator connected to a first inverter and a second stator connected to a second inverter. A motor controller controls a supply of first three-phase currents from the first inverter to the first stator, and controls a supply of second three-phase currents from the second inverter to the second stator. Each of the first three-phase currents has a same-phase first compensation current superposed thereon, and each of the second three-phase currents has a same-phase second compensation current superposed thereon. The second compensation current has the same phase as the first compensation current and is reversely polarized relative to the first compensation current.

Abstract: A brushless DC motor utilizing a single pole double throw reed switch as a rotor position sensor. In one embodiment, the motor has a four-pole internal stator with bifilar windings providing alternating polarization for each subsequent pole, and a hollow outer rotor with radially magnetized ring-shaped permanent magnet. The rotor magnet has magnetically uninterrupted four-pole torque generating surface and incorporates features to interact with the reed switch. A non-uniform air gap between the stator poles and an inner surface of the rotor magnet allows generating a complementary reluctance torque between the energization pulses. The motor includes means to limit the electric current through the reed switch.

Abstract: A magnetically isolated phase stator includes a stator phase section with two sides and a magnetically inactive isolation region on each side that prevents a permanent magnetic field from being shared from the stator phase section and another stator phase section of the stator. A magnetically isolated phase interior permanent magnet electrical rotating machine includes a magnetically isolated phase stator, a rotor, and an air gap between the stator and rotor defining a rotor-stator interface, the rotor having two or multiples of two permanent magnets arranged in parallel with opposing magnetic poles to direct magnetic flux through a pole of the rotor, through the air gap of the rotor-stator interface, and through a pole of the stator.

Abstract: A motor control system for deployment in high temperature environments includes a controller; a first half-bridge circuit that includes a first high-side switching element and a first low-side switching element; a second half-bridge circuit that includes a second high-side switching element and a second low-side switching element; and a third half-bridge circuit that includes a third high-side switching element and a third; low-side switching element. The motor controller is arranged to apply a pulse width modulation (PWM) scheme to switch the first half-bridge circuit, second half-bridge circuit, and third half-bridge circuit to power a motor.

Abstract: A motor includes a frame, a shaft rotatably mounted onto the frame, and at least one disc mounted onto the shaft. At least one permanent magnet is mounted on the disc, and at least one electromagnet and at least one coil are mounted to the frame in rotational magnetic proximity to the permanent magnet. A battery is connectable to the electromagnet and the coil for energizing the electromagnet and for receiving electrical current from the coil for charging the battery. A relay switch controls the transmission of electrical power from the battery to the electromagnet. A sensor generates a signal to the relay switch to activate electrical power to the electromagnet upon sensing that the permanent magnet is positioned with respect to the electromagnet such that a magnetic force generated by the electromagnet would be effective for inducing movement of the permanent magnet and consequent rotation of the disc.

Abstract: Dynamic reconfiguration-switching of motor windings is optimized between winding-configurations. Acceleration is traded off in favor of higher velocity upon detecting an electric motor is at an optimal angular-velocity for switching to an optimal lower torque constant and voltage constant. The total back electromotive force (BEMF) is prohibited from inhibiting further acceleration to a higher angular-velocity.

Abstract: A motor includes a base plate, a stator, a rotor, a circuit board and a Hall element. The stator is disposed on the base plate. The rotor is disposed around the stator, and includes a rotating shaft and a magnetic assembly. The rotating shaft is extended to a center part of the stator. The magnetic assembly includes plural magnets. The circuit board is arranged between the stator and the base plate and comprises a Hall element. A first gap and a second gap are arranged between every two adjacent magnets. The first gap is in the vicinity of the Hall element, and opposed to the second gap. The distance of a vacant portion of the first gap is shorter than the distance of the second gap, thereby facilitating continuous and steady magnetic induction between the Hall element and the magnetic assembly.

Abstract: A motor-driven compressor is provided that includes a housing made of a metal material, a compression portion, an electric motor, a cover made of a metal material, a motor drive circuit accommodated in an accommodation space defined by the housing and the cover, an elastic sealing member located between the housing and the cover, and an extended portion provided in at least one of the housing and the cover. The compression portion and the electric motor are accommodated in the housing. The cover is attached to the housing. The motor driver circuit drives the electric motor. The extended portion extends in a direction toward an opposing one of the housing and the cover and is arranged inside the sealing member. The extended portion includes an outer peripheral surface. The sealing member is arranged to be in close contact with the outer peripheral surface of the extended portion.

Abstract: A high lift system for an aircraft, which extends and retracts the landing flaps of the aircraft in a fully electric manner. In this context, a fully electric drive is used, comprising an electric motor having an internal redundancy, in such a way that the electric motor is configured as a fault-tolerant electric motor. It may thus be possible to do without a coupling gear unit in the electric motor.

Abstract: An electrical machine (10) has three phase windings (12). Each phase winding (12) is connected to a respective current source (18). Each current source 18 provides alternating current to the corresponding winding (12). The current source 18 is connected independently to the respective winding (12). The electrical angles of the phase windings (12) are so arranged that none of the phase windings (12) has a zero torque angle which coincides with a zero torque angle of another phase winding (12).

Abstract: A drive unit for an electric motor comprises a multilevel inverter and a battery. The battery comprises at least one battery module train comprising a plurality of battery modules connected in series, each module having at least one battery cell and one coupling unit. The at least one battery cell is connected between a first input and a second input of the coupling unit. The coupling unit is designed to connect the at least one battery cell between two terminals of the battery module in response to on a first control signal and to connect the two terminals in response to a second control signal. Several center taps are arranged on the battery module train, by means of which a potential can be tapped at a connection between two battery modules respectively. Inputs of the multilevel inverter are connected to the taps.

Abstract: A blood pump system for left ventricle assist has an implantable pump unit having a multiphase stator having a plurality of windings connected between respective junctions for forming first, second, and third phases. An external control unit comprises an H-bridge inverter having first, second, and third phase legs. A percutaneous cable is provided having first, second, and third parallel pairs of redundant conductors. Each conductor pair is connected between a respective phase leg and a respective junction. The conductors are arranged concentrically around a cable core so that individual conductors of each pair are separated by at least one conductor of a different conductor pair.

Abstract: Starting from the known rotating electromechanical converter comprising a stator with magnetic circuits and polyphase energizing windings, a first, inner, rotor with magnetic circuits and polyphase energizing windings, and a second (inter)rotor between this first rotor and the stator, provided with permanent magnetic members for co-operation with the magnetic circuit of at least the stator, the invention proposes to provide means for modifying the state of magnetization of at least a part of the respective areas of the second rotor which each lie between two successive permanent magnetic members.

Abstract: Dynamic reconfiguration-switching of motor windings in a motor is optimized between winding-configurations by selectively lowering resistance of a constantly used portion of one of the motor windings. Acceleration is traded off in favor of higher velocity upon detecting the electric motor in the electric vehicle is at an optimal angular-velocity for switching to an optimal lower torque constant and voltage constant. The total back electromotive force (BEMF) is prohibited from inhibiting further acceleration to a higher angular-velocity.

Abstract: Dynamic reconfiguration-switching of motor windings is optimized between winding-configurations. Acceleration is traded off in favor of higher velocity upon detecting a brushless DC motor is at an optimal angular-velocity for switching to an optimal lower torque constant and voltage constant. The total back electromotive force (BEMF) is prohibited from inhibiting further acceleration to a higher angular-velocity.

Abstract: Dynamic reconfiguration-switching of motor windings in an electric motor in an electric vehicle is optimized between winding-configurations. Acceleration is traded off in favor of higher velocity upon detecting the electric motor in the electric vehicle is at an optimal angular-velocity for switching to an optimal lower torque constant and voltage constant. The total back electromotive force (BEMF) is prohibited from inhibiting further acceleration to a higher angular-velocity.

Abstract: Dynamic reconfiguration-switching of motor windings is optimized between winding-configurations. Acceleration is traded off in favor of higher velocity upon detecting a tape storage drive is at an optimal angular-velocity for switching to an optimal lower torque constant and voltage constant. The total back electromotive force (BEMF) is prohibited from inhibiting further acceleration to a higher angular-velocity.

Abstract: An exterior rotor switched reluctance machine includes a stator, a rotor adjacent the stator and adjacent a housing, the housing connected to the stator. The stator further includes a back iron, a set of stator poles connected to the back iron and a set of windings disposed between the set of stator poles. The rotor, connected to a shaft and rotatively coupled to the stator, further includes a set of rotor segments. The set of windings includes a set of phases, each phase experiencing a flux linkage that varies with an angular position of the rotor. The apparatus operates as a motor in response to selectively energizing the set of phases with a set of current pulses. The apparatus operates as a generator in response to rotating the shaft.

Abstract: A system for providing operating or charging current supply in different modes of operation includes an electric machine including a rotor and a stator having stator windings, at least one charge storage device, such as a battery, and an inverter disposed between the charge storage device terminals and the electric machine. A contact arrangement modifies electrical interconnections between phases of the inverter and the stator windings. In a supply mode, the electrical interconnections are controlled so that each inverter phase is electrically interconnected with a stator winding set having windings separated from each other by stator windings in other winding sets for driving the rotor of the electrical machine. In a charge mode, however, these interconnections are controlled so that each inverter phase is electrically interconnected with a stator winding set having windings directly adjacent to each other and are not separated from each other.

Abstract: An air-cooled heat exchanger (ACHE) for cooling process fluids used in an industrial process. In one embodiment, the ACHE is configured as a forced-draft ACHE. A support structure supports the forced draft ACHE above grade. A tube bundle is supported by the structure and is configured to receive process fluids used in an industrial process. A plenum is connected to the support structure, positioned beneath the tube bundle and configured to direct air-flow through the tube bundle. A fan is supported by the support structure and positioned beneath the plenum. Rotation of the fan produces an air-flow that is directed through the tube bundle by the plenum. A fan drive system is supported by the support structure, positioned beneath the fan and comprises a permanent magnet motor comprising a motor casing, a stator and a rotatable shaft, the rotatable shaft being connected to the fan.

Abstract: A controller for use with a motor including a stator, around which three-phase coils are wound, and a rotor, which includes a magnet functioning as a first magnetic pole and a salient pole of a core functioning as a second magnetic pole. The controller supplies the three-phase coils with excitation currents having a predetermined phase difference from one another to drive and rotate the rotor. The controller includes a current adjustment unit that adjusts a fundamental wave current using high-order currents for third order and ninth order components in a q-axis to reduce torque ripple. The excitation current is generated based on the fundamental wave current adjusted by the current adjustment unit.

Abstract: An electrical machine system including a permanent magnet assembly having a magnetic field and a plurality of conductive coils, the magnet assembly and coils arranged for relative rotation between the coils and magnetic field in the manner of an electrical generator or motor, the system further comprising a current injector electrically connected to said coils and arranged selectively to supply a current signal thereto, the current signal being asynchronous with the frequency of rotation between the permanent magnet assembly and coils so as to heat and thereby demagnetise one or more magnet within said permanent magnet assembly.

Abstract: A method of controlling a brushless motor that includes rectifying an alternating voltage to provide a rectified voltage, and exciting a winding of the motor with the rectified voltage. The winding is excited in advance of predetermined rotor positions by an advance period and is excited for a conduction period over each electrical half-cycle of the motor. The length the advance period and/or the conduction period is defined by a waveform that varies periodically with time. The method then includes adjusting the phase of the waveform relative to the alternating voltage in response to a change in one of motor speed and RMS value of the alternating voltage. Additionally, a control system that implements the method, and a motor system that incorporates the control system.

Abstract: A brushless direct current (DC) motor includes a rotor, a stator and a driving unit. The rotor includes a plurality of magnetic poles. The stator includes a plurality of upper pole arms and a plurality of lower pole arms. The driving unit includes at least two coils wound on the upper pole arms and the lower pole arms respectively, and the driving unit generates an alternating magnetic field on the stator for driving the rotor.

Abstract: An air-cooled heat exchanger (ACHE) for cooling process fluids used in an industrial process. In one embodiment, the ACHE is configured as a forced-draft ACHE. A support structure supports the forced draft ACHE above grade. A tube bundle is supported by the structure and is configured to receive process fluids used in an industrial process. A plenum is connected to the support structure, positioned beneath the tube bundle and configured to direct air-flow through the tube bundle. A fan is supported by the support structure and positioned beneath the plenum. Rotation of the fan produces an air-flow that is directed through the tube bundle by the plenum. A fan drive system is supported by the support structure, positioned beneath the fan and comprises a permanent magnet motor comprising a motor casing, a stator and a rotatable shaft, the rotatable shaft being connected to the fan.