hybrid bicycle powered by re-chargeable lead acid batteries. The aim of this paper is to design an electronic control unit for brushless DC (BLDC) motors in an ...
synchronous motor. Keywords: Operational; characteristics; bldcm. 1. Introduction. Brushless dc motors are rapidly gaining popularity in the appliance, ... Three-phase brushless dc motors are operated by energizing two of its three phase windings at
In this chapter, the basic structures, drive circuits, fundamental principles, ... Fig.2 Brushless dc motor = Permanent magnet ac motor + Electronic commutator.
cancel each other. This strategy was first suggested by. Ackermann . Finite element simulations of this technique yield a multiplicity of zero-cogging solutions, as shown in Figure 5. 0. 2. 4. 6. 8. 10. 12. 14. 16. 18. 20. 0. 2. 4. 6. 8. 10. 12. 1
Park and Clarke mathematical transformation library for AVR32 UC3 microcontroller. â¢ Theory of Field Oriented Control. â¢ PC application for real time motor ...
Keywords: brushless dc motor, fuzzy controller, sensorless. SÅowa kluczowe: .... Here we use three manual switches to change from one strategy to the other.
Jul 19, 2010 - BLDC motors, also called Permanent Magnet DC Synchronous motors, are one of the motor types ... The brushless DC motor is a synchronous electric motor that, from a modelling perspective, looks ..... intervals and aligned properly with
sensorless control of brushless dc motors using an adaptive sliding mode ... brushless dc motor are controlled to generate constant torque ... the sliding modes in the fields. ..... T. W. Nehl et al., âDynamic simulation of radially oriented perma-
but any reference to ATmega48 in this document also applies to ATmega88/168. 8-bit. Microcontrollers. Application Note. Rev. 8012A-AVR-10/05 ...
the use of the BEM software in the design of brushless DC motors. Integrated Engineering ..... Stratton, J.A. Electromagnetic Theory. McGraw Hill Book Co., New ...
technique used in a permanent magnet brushless sensorless drive. Various existing ... (2), where L is self inductance, Î» represents flux linkage due to permanent magnet attached to the rotor which .....  C. Uang, Z. Ho, P. Wang and S. Liu, Senso
the BLDC motors. In BLDC motor, the commutation of a BLDC motor is controlled electronically. To rotate the BLDC motor the stator windings should be energized in a sequence. It is important to know the ... P controller, PI controller, PD controller a
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good power factor in wide speed range of the drive. Keywords: PMBLDCM drive, Power factor correction, Cuk converter,. Air-conditioning, VSI. 1. Introduction. A permanent magnet brushless DC motor (PMBLDCM) is a kind of three-phase synchronous motor h
the electromagnetic torque; no other parameters such as winding resistances, inductances are needed. ... motor theory which correlated electromagnetic torque with motor speed. The equation required information such as back EMF constant, phase resista
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Abstract-This paper proposes an efficient control framework that utilizes de-de converters to achieve flexible power flow control in multiterminal de (MTDC) grids. The de-de converter employed in this paper is connected in cascade with the de transmi
Today's brushless drive systems include motors made with the robust 3 rd generation ... applications on extruders, wire drawers, winders, cranes, cable tensioners, conveyors ... performed on a blow-molding machine of Brush DC versus.
Mar 14, 2016 - reduction of the complexity in the design of the control scheme for the ... topology can be addressed to on-chip practical implemen- tations, since no ... In these sys- tems, the supply modulator, usually a switching regulator.
Field Oriented Control, or Vector Control, is preferred in systems ... the axis. Figure2: ARMÂ® CortexTM-M3 microcontroller with integrated hardware based ... sinusoidal control. By manipulating the motor currents and voltages with reference to the r
CHAPTER 4: ANALYSIS OF ROTOR FAULTS IN BLDC MOTORS. OPERATING AT CONSTANT SPEED. ...... Figure 4.2: BLDC motor - DC generator test rig .
DC voltage to each motor. In this paper first the principle of reduced-cable smart motors is described, followed by the architecture of signal transmission system ...
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This paper presents an educational tool developed for neural network (NN) control of brushless. DC (BLDC) motors. Neural networks courses are widely offered at the graduate and under- graduate level due to the successful applications of neural networ
Power Losses in Outside-Spin Brushless D.C. Motors P. Andrada, M.Torrent, J.I.Perat, B. Blanqué Departament d’Enginyeria Elèctrica (Universitat Politècnica de Catalunya) EPS d’Enginyeria de Vilanova i la Geltrú Avda. Víctor Balaguer, s/n, 08800 Vilanova i la Geltrú (Spain) Telf. +34 938967732; Fax:+34 938967700, e-mail: [email protected]
Outside-spin brushless D.C. motors are an alternative to conventional D.C. brush permanent magnet motors, especially in applications that require low power and costs and in which high inertia effects are advantageous. This paper presents a procedure for computing power losses in these kinds of machines. Expressions are derived for predicting copper losses, power interrupter losses, stator iron losses in the tooth and in the yoke, mechanical losses, friction and windage. Stray load losses are also considered and evaluated from previous measurements in outside-spin brushless D.C. motors. The results obtained from the approach proposed are compared to those measured on existing motors, showing a good agreement.
Key words Outside-spin motors, brushless D.C. motors, copper losses, iron losses, mechanical losses, stray losses, efficiency.
1. Introduction Outside-spin brushless D.C. motors or brushless D.C. motors with outer rotor have deserved increasing attention in the market of low cost and low power applications that require constant speed, such as motors for fans, motors for office automation (copiers, printers, etc.) and, in general, applications in which high inertia effects are beneficial to the system’s performance. These applications, usually powered by permanent magnet D.C. brush motors, demand quieter motors, low EMI levels and require no maintenance. Outside-spin brushless D.C. motors are specially intended for applications that require thin motors (short length and long external diameter). Outside-spin brushless D.C. motors have several advantages over inner-rotor brushless D.C. motors. They have a greater magnet surface, which therefore allows larger airgap and leads to a reduction in mechanical tolerances. In addition, they are less costly to wind. In this paper, a procedure for the determination of power losses in three-phase outside brushless D.C. motors is reported. In this procedure, all kinds of losses (copper, power interrupter, iron, mechanical and stray load losses) are considered and their influence on torque production is studied. This procedure is suitable for design studies that require the fast evaluation of motor performance and in
loss evaluation prior to using finite element analysis. The results calculated with the procedure proposed are compared to the experimental results.
2. Drive Description An outside-spin brushless D.C. motor has an electromagnetic structure, which is formed by an outer rotor that has a permanent magnet arrangement enclosed by soft magnetic steel housing and a stator assembly that consists of a lamination stack with coils wrapped around the stator tooth (Fig. 1). Most of its applications are in the low power (up to 250 W), low voltage (12, 24 V) and moderate speed (slightly over 3000 rpm) ranges. Thin motor design requires a high number of poles to reduce core back iron and end-windings, and that number is only limited by frequency considerations. If good performance and low torque ripple are drive requirements, a threephase star-connected motor associated with an inverter with six power switches (Power Mosfet, due to the values of voltage and current managed) is the best choice. Usually, three Hall latch sensors are enough for position determination. Low cost requirements mean that ferrite magnets must be used and electric loading must be increased. As a consequence, a large slot area must be adopted. In addition, the power converter and control must find room inside the motor (Fig. 2).
Fig. 1. Cross section of an eight-pole outside-spin brushless D.C. motor
Fig. 2. Block diagram of an outside-spin brushless D.C. motor drive where ρ 20 º is the copper resistivity; N f are the number
3. Determination of Power Losses Power losses in electric motors are an important issue because these losses determine the efficiency of the motor and its heating. High efficiency cuts the operating costs, contributes to energy saving and reduces gas emissions. Moderate heating increases safety. High efficiency in outside brushless D.C. motors can offer a competitive advantage over conventional drives. The following expressions are derived in order to predict copper losses, power interrupter losses, stator iron losses in the tooth and in the yoke, mechanical losses, friction and windage. Stray load losses are also considered and evaluated from previous measurements.
Copper losses at a specified temperature θ are computed by means of the following equation: 2 pcuθ = 3 kθ R20 º I RMS (W)
2 (A) 3
235 + θ 255
Phase resistance is calculated by means of the expression: Nf sc
l em (Ω)
The I flat top current (A) coincides with the D.C. current input. Equation (4) can be substituted in Equation (1) to give:
Skin effects can be neglected because, in outside-spin D.C. motors in the range considered, the skin depth δ is usually higher than the wire size dc, that is:
where kθ is the temperature correction factor given by:
R 20 º = ρ 20 º
I RMS = I
p cu θ = 2 kθ R20º I 2 (W)
A. Copper Losses
of turns per phase; s c is the conductor cross section and l em is the mean coil length. If we consider, in a first approximation, an ideal 120º square wave, then:
>> d c
B. Power Interrupter Losses If we consider that, in a steady state, there are always two switches in the ON state, the losses across the power interrupters pint, can be evaluated by: p int = 2 RON I 2 (W)
where RON is the resistance of the power switch in the ON state.
p y = k h f Bαy +
C. Iron Losses The specific iron loss for a sinusoidal magnetic field is expressed by means of the well-known Steinmetz equation: PFe = k h f Bˆ α + k e f
Bˆ 2 (W/kg) (8)
Note that the hysteresis loss term is unchanged as it depends only on the peak value of the flux density, assuming that there are no minor hysteresis loops. By following this approach, expressions for the iron loss are derived in order to predict the hysteresis and eddy current losses in the stator tooth and in the stator yoke,  to . 1). Iron Losses in the Stator Teeth Specific iron losses in the teeth pt , including hysteresis and eddy current losses, can be determined using the following expression: 4
where Bˆ y is the yoke flux density and β m (elec. rad.) is the magnetic pole arc.
The total iron losses p Fe in the stator core, if we ignore surface loss, are calculated by means of the equation: p Fe = p t G t + p y G y (W)
where pt and py are the specific losses (W/kg) in the teeth and stator yoke and Gt and Gy are the weights (kg) of the tooth and stator yoke respectively.
The mechanical losses pmec are subdivided in two parts: friction losses pfr and windage losses pwind: p mec = p fr + p wind (W)
where Bˆ t is the teeth flux density and α tt is the augmented tooth arc that can be expressed by: ⎛ π k c wo ⎞ − ⎟ (elec. rad.) D ⎠ ⎝ s and γ = 1 if α tt ≤ π − β m
α tt = p⎜
π − βm ⎞ ⎛ or γ = ⎜ 2 − ⎟ (elec. rad.) if α tt > π − β m αtt ⎠ ⎝ where s is the slot number, kc is the Carter coefficient, w0 is the slot opening and D is the stator diameter. 2). Iron Losses in the Stator Yoke
Specific iron losses in stator yoke py , including hysteresis and eddy current losses, can be determined using the following expression:
Friction losses in bearings can be determined using the following formula: p fr ≈
p t = k h f Btα +
f 2 Bˆ y2
D. Mechanical Losses 
k ⎛ dB ⎞ = k h f B + e2 ⎜ (W/kg) ⎟ 2π ⎝ dt ⎠ RMS
3). Stator Core Loss
where the first term is the hysteresis loss and the second is the specific eddy current loss. Bˆ is the peak value of flux density and β, kh, α and ke are constants determined by curve fitting from the manufacturer’s data. The iron loss expression in (8) is only valid for sinusoidal flux density. In brushless D.C. motors, the variation of flux in the stator core is not sinusoidal. Under these conditions, an alternative approach for specific iron loss is given by: ˆα
3 n r Grot N ×10 −3 (W) 2
where nr is the number of bearings, Grot is the rotor weight, and N is the speed (rpm). Windage losses are evaluated by the formula: 3 p wind ≈ 2 Dout L N 3 × 10 −6 (W)
where Dout is the outside rotor’s diameter (m), and L is the rotor’s length (m). E. Stray Load Losses
Stray load losses are defined as the losses that arise from the non-uniform distribution of a current in copper. They also encompass additional core losses that are produced in iron by the distortion of magnetic flux by a load current. It is common practice to evaluate stray losses as a percentage (3 to 5%) of the output power of small machines rated up to 10 kW . Nevertheless, several tests performed on outside brushless D.C. motors working at constant speed show that these kinds of losses increase markedly with the load and under these conditions frequency has no influence. In addition, current waveforms are not ideal 120º square waves, which clearly contribute to increasing the amount of copper losses. Therefore, stray load losses can be estimated by means of the following empirical expression:
⎛ 2 ⎞⎟ ps = 2 ⎜ λ − R I x (W) ⎜ ⎟ 20 º 3 ⎝ ⎠
D.C. motor (Table I). The computed power losses are compared to the data tested. From a non-load test at different speeds, the stator core, windage and friction losses are obtained (Fig. 3). From a load test, in which the outside-spin brushless D.C. motor is connected to a dynamometer, efficiency versus load is reported (Fig. 4). Very good agreement is derived from the non-load test; therefore, the computation of stator core and mechanical losses based on the expressions proposed is suitable for this kind of motor. The efficiency calculated under different load conditions shows significant variations at loads lower than 0.5 p.u., compared to values obtained experimentally, although there is fairly good agreement in the range of 0.5 p.u. to 1.25 p.u.
I RMS and is usually between 0.86 and 0.84, I and exponent x may be evaluated range from 2.8 to 3.6.
where λ =
4. Procedure Verification The proposed procedure for determining power losses is applied to an existing eight-pole outside-spin brushless
TABLE I. - Main Characteristics of an Eight-Pole Outside-Spin Brushless D.C. Motor
Voltage Torque Current Speed Output diameter Total length Permanent magnets Lamination
12 V 20 Ncm 7A 2500 rpm 95 mm 40 mm Ferrites FXD 4 A Br =415 mT M-600-65 A
Core, friction and windage losses (W)
12 11 10 9 8 7 6 5 4 3 2 1 0 0
Speed (rpm) Fig. 3. Core friction and windage losses versus speed. The straight line was obtained using the expressions proposed, and the points were obtained experimentally
80 70 Efficiency (%)
60 50 40 30 20 10 0 0
Fig. 4. Efficiency (%) versus load (p.u.). The straight line was obtained using the expressions proposed, and discontinuous line shows the experimental results
The paper describes a procedure for power loss determination in outside-spin brushless D.C. motors. In the procedure proposed, expressions are derived for predicting copper losses, power interruption losses, stator iron losses in the tooth and in the yoke, mechanical losses, friction and windage. Stray load losses are also considered and evaluated from previous measurements. Power loss determination using the methodology explained show good agreement with the experimental results obtained from the tests. The procedure proposed is suitable for design studies that require a fast evaluation of motor performance and in loss evaluation prior to using finite element analysis.
 T. J. E. Miller and R. Rabinovici. “Back-EMF Waveforms and Core Losses in Brushless D.C. Motors”. IEE Proc. Electr. Power Appl., Vol. 141, No. 3, May 1994, pp. 144-154.  G. Slemon and X. Liu. “Core Losses in Permanent Magnet Motors”. IEEE Transactions on Magnetics, Vol. 26, No. 5, September 1990, pp. 1653-1655.  C. Mi, G. Slemon, R. Bonert. “Modeling of Iron Losses of Permanent-Magnet Synchronous Motors”. IEEE Transactions on Industry Applications, Vol. 19, No. 3, May/June 2003, pp. 734-742.  Deng. “An Improved Iron Loss Estimation for Permanent Magnet Brushless Machines”. IEEE Transactions on Energy Conversion, Vol. 14, No. 4, December 1999, pp. 1391-1395.  J. F. Gieras and M. Wing. Permanent Magnet Motor Technology, Design and Applications. Marcel Dekker, New York 1997.
Acknowledgement The authors would like to thank DOGA S.A., who provided outside-spin brushless D.C. motors for testing and particularly Hans Baudaug and Fermi Lacoma for their support.