USER MANUAL: PERMANENT MAGNETS ELECTRIC MOTORS
Contents
1. N H in dg HE q r pas aS N E x a 4 i LH i ct DUU E TI AnS NSN om N T EVE ZL aE i Be E A ae Ate A AEE TTS G i wrpg e AE N L2 reee A A eu gt hope e N PA SZAN AN Fig 2 2 Cross section of the ACBL motor WWW ICpe rOo icpe S A Splaiul Unirii 313 030138 Bucuresti RO 423140 J40 21438 92 tel 021 589 33 00 tax021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 email Office icpe ro MKB NexteBank Energy service company Electrical engineering company Research institute for electrotechnics yo ICPE er and for the development of a motor heat constant as good as possible the stator is free of housing ACBL can be delivered in the variant with or without electromagnetic brake The rotor position sensor is of the electromagnetic type brushless resolver from the internal output of the photo electronic encoder type at the same time it can be delivered without position sensor DCBLs have the same mechanical construction as ACBLs These motors are provided with the rotor position sensor of the magnetic type the Hall sensor On demand the DC or AC brushless electric motors can also be offered in the direct drive design 3 The operating principle of the permanent magnets electric motors 3 1 DC commutator brush motor In order to explain the operating principle of the DC brushed motor one considers its simplest constructive variant consisting of2. a A tars OHSAS 18001 awe nI c c ag re AR R al Net a tel 021 589 33 00 tax 021589 34 34 RO40 CRDZ 024A 0863 9047 6001 eaves email Office icpe ro MKB NexteBank wE Energy service company Electrical engineering company Research institute for electrotechnics ICPE cx al slowly This saturation of the the speed increase is described by the mechanical time constant in Fig 4 4 2 and is defined by the following relation R T R SAU Tm Jr efid ko J R M M were Jsis the load inertia moment In this case the maximum acceleration is defined by the following relation 4 Ai Omax 10 J n J Kw Ms U constant karan ji At Time Fig 4 4 2 Saturation of the time speed increase for the starting at constant voltage The no load starting time up to the operating point is M M 1 a hn At p In a O OOR A M M r a R 4 5 Operating point In the case of the motor supply with the rated voltage Un and at the rated current Iy the operating point is shown in Fig 4 5 1 Speed n Torque M I Current Fig 4 5 1 Establishing the operating rated point WWW ICpe ro icpe S A Splaiul Unirii 313 030138 Bucure ti RO 423140 J40 21438 92 tel O21 589 33 00 fax 021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 email Office icpe ro MKB NexteBank Energy service company Electrical engineering company Research institute for electrotechnics ICPE 7 se 7
3. Energy service company Electrical engineering company Research institute for electrotechnics ICPE lt r he resultant force on a conducting wire of l length generates an electromagnetic torque whose expression is M Fxr In reality a motor winding is made up of several turns distributed to the rotor lamination stack slots and their ends terminals are connected to the commutator lamellas on which the commutator brushes slide their number being equal to the pole number of the motor Fig 3 1 2 Crestaturi Perii Fig 3 1 2 The rotor commutator shaft and brushes of a DC motor The electric current in the rotor turns changes its direction at each passing of the conducting wires close to the axis of the brushes Fig 3 1 3 Consequently the wave form of the rotor currents shows a time alternative variation of rectangular shape Therefore the piece that changes the direct current at the level of the motor terminals into alternative current at the level of the turns is the commutator In case the DC motors are used as servomotors there occurs the necessity of an accurate control of the speed at various loading levels of the motor a rapid response to sudden variations of the load torque respectively Miez magnetic stator si rotor Magnet permanent Magnet permanent Conductor Intrefier Conductor Liniile campului magnetic Fig 3 1 3 Path of lines of field and the direction of currents wi
4. strictly linear In general with this type of motors the diameter is much smaller than the axial length 4 2 Steady state operation Maximum continuous torque Mc Mn maximum permissible speed Nmax Nn From a mechanical viewpoint the motor steady state operation can be at maximum continuous torque or at maximum permissible speed The operation of the motors under these limits is stable and reliable The inadmissible increase of these parameters causes the wear of the switching system and finally the motor premature failure Fig 4 2 1 shows the diagram of the motor maximum permissible steady state operation Speed rpm 25000 Max permissible speed Maxirnal 20000 continous torque 15000 10000 Short term 5000 operating range 10 20 30 40 Torque mMNm 0 4 0 8 1 2 Current A Fig 4 2 1 WWW ICpe ro icpe S A Splaiul Unirii 313 030138 Bucure ti RO 423140 J40 21438 92 tel 021 589 33 00 tax021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 email Office icpe ro MKB NexteBank Energy service company Electrical engineering company Research institute for electrotechnics yo ICPE py Soren current Ic environment temperature To and winding imum temperature Tw The absorbed current generates Joule losses while passing through the rotor winding which function the heat delivery surface and the environment temperature To C must be dissipated so that the winding temperature will not excced the maximum p
5. Energy service company Electrical engineering company Research institute for electrotechnics hi ICPE lt USER MANUAL PERMANENT MAGNETS ELECTRIC MOTORS 1 Generalities The present manual refers to three types of electric motors designed and developed in ICPE Department 4 e DC brushed permanent magnets motors hereinafter referred to as TM and TE respectively e AC brushless permanent magnets motors hereinafter referred to as ACBL e DC brushless permanent magnets motors hereinafter referred to as DCBL These electric motors are designed for the adjustable speed drives within the large range and at the same time they represent a solution to complex applications semiconductor manufacturing process terrestrial and aerospace actuating guiding systems etc The adjustable speed drives represented a field in which the DC commutator brush electric motors held the supremacy beacause of the simplicity with which the rotational speed could be adjusted in a very wide range and with special dynamic performances it was practically the only solution for the high technology applications At the same time the performances imposed to the machine tools industrial robots aerospace applications efficiency heavy duty inflammability explosion advanced vaccum maintenance increased the DC commutator brush electric motors proved to be ever less adequate Within this context it was necessary to remove the commutator brushes subassem
6. Ion Iv function the loading degree Angular acceleration a inertia moment of the rotor and of the load JRs Starting at constant current the motor generates a constant torque to a constant acceleration and which a speed linear increase correspond till the operating point is reached Fig 4 3 2 WWW ICpe ro icpe S A aN Splaiul Unirii 313 030138 Bucure ti RO 423140 J40 21438 92 amp S ES tel O21 589 33 00 fax 021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 D il Office icpe ro MKB NexteBank Energy service company Electrical engineering company Research institute for electrotechnics constant n ah My Ng Fig 4 3 2 Starting at constant current representation on the mechanical characteristic The angular acceleration is defined in the relation a 1o4 ul o rad s 4 3 1 Ja tda Ja dg Load starting time Ma Age ine 4 3 2 300 k 1 In the case of starting at constant voltage Fig 4 4 1 the torque increases from the torque value to the null speed Mz along the speed torque linear characteristic up to the rated torque My Speed n usu n Ma M Torque M k I Current Fig 4 4 1 Starting at constant voltage Speed torque characteristic The bigger the torque is the higher the acceleration will be The acceleration decreases together with the speed increase and the speed www icpe ro _icpe S A Splaiul Unirii 313 030138 Bucuresti RO423140 4J40 21438 92 ESV egek
7. a rectangular turn with the length l and the width 2r placed between the poles of a permanent magnet Fig 3 1 1 The considered turn can rotate freely around its rotational longitudinal axis within the constant and uniform field of magnetic induction B established between the magnetic poles N and S The turn ends are connected to a DC source through a commutator brushes subassembly forming a closed circuit At the considered moment the turn plane is coplanar to the magnetic induction direction Beacause of the fixed position of the brushes P and P2 they will successively be in contact with the two lamellas of the commutator The sliding contacts enable the current sense reversing through the turn when the turn plane is perpendicular to the magnetic induction direction The electromagnetic torque generated by the motor is the result of the interaction between the induction field B and the electric current of intensity I passing through the turn The force acting on each conducting wire of l length at the considered moment results from the composition of the elementary forces dF considered on the elements dl of the length of theconducting wires dF i1dalxB Fig 3 1 1 The operating principle of the DC brushed motor es ees TS SA WWW ICpe ro ___siicpeS A vam Splaiul Unirii 313 030138 Bucuresti RO 423140 J40 21438 92 be S ESYO tel 021 589 33 00 tax021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 D nail Office icpe ro MKB NexteBank
8. assembly speed transducer and electromagnetic brake According to Fig 2 1 which shows a Stator Rotor Tahogenerator Sbs colector peri 1 II Imee minili it lll HE Fig 2 1 Cross section of the TM motor motor cross section the rotor is made up of stamped laminations iron silicon with alloted slots to which a DC winding is distributed In the stator there are distributed SPM technology permanent magnets rare earths The brake is of the permanent magnets electromagnetic type and the speed tranducer is of the analogical type DC permanent magnets tachogenerator The commutator brushes subassembly has a classic design and is provided with two parallel current paths ACBLs have a reverse mechanical configuration in relation to TM or TE in the sense that the permanent magnets are distributed SPM technology or function the application of the IPM technology to the rotor The stator is made up of stamped laminations iron silicon with alloted slots to which a polyphase winding is distributed The main characteristic of this type of electric motor is the lack of the commutator brushes subassembly Fig 2 2 shows the motor cross section The design is with Borne conexiune w Scut tractiune Rotor Stator i al d Resolver SALELLLLL LX AWT lt lt lt 7 ATIE if LEd LLL HEHH nE
9. bly and its function was taken over by very complex electronic architectures as well as by position and or speed inductive sliding contact free tranducers After the 1990s the manufacturing costs of the inductive transducers and of the movement control electronic architectures decreased considerably in relation to the manufacturing costs of the DC electromagnetic excitation or permanent magnets electric motors fact that finally imposed the acceptance of these drive systems on the market ICPE Department 4 manufactures permanent magnets brushed and brushless electric motors in a bearing design at a rated speed of 4000 min and the rated torque of 1 9 Nm On demand there can be performed DCBL with other parameters or in a direct drive design The transducers used are from the current production resolver or tachogenerator On demand they can be delivered with Hall sensors or in the sensorless variant The productmanufactoring is in accordance with the requirements SR EN ISO 9001 SR EN ISO 14001 SR OH SAS 18001 WWW ICpe ro icpe S A Splaiul Unirii 313 030138 Bucure ti RO 423140 J40 21438 92 tel O21 589 33 00 fax 021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 il Office icpe ro MKB NexteBank Energy service company Electrical engineering company A Research institute for electrotechnics CPE 2 Mechanical configuration The main components of TM and TE respectively are the following stator rotor commutator brushes sub
10. ermissible value insulation class Tw C At the same time the winding maximum temperature must be correlated to the mark of brushes Hence in the case of copper graphite brushes due to the fact that the winding cane bear a high current density the rotor maximum temperature can be 125 C 155 C In the case of the silver graphite brushes it cannot exced 85 C 4 3 Short time regime operation Winding heat constant tw In some applications for short periods of time it is necessary to load or stress the motor over the values corresponding to the continuous rating Thus in the case of the short time regimes intermittent the rated current value can be exceeded In general the time for which the value of the current Ic can be exceeded is about 60 seconds for motors with diameters 60mm 90mm Fig 4 3 1 shows the ratio dependence the operating current and the rated current Jon Jn function the ratio of the operating current ON to the motor rest time In general if the motor has a large cooling surface the overload standing time increases The exact calculation of the overload current depends on the rated current value and the environment temperature 4 4 Operating dynamic regimes The most important regimes are the starting and the acceleration up to an imposed speed These are performed at constant current voltage 10 20 30 40 50 60 70 80 90 ON Fig 4 3 1 Ratio of the maximum current to the rated one
11. ily In order to exemplify the operating principle of the brushless motor Fig 3 2 1 shows four rotor stator relative distinct positions for a two pole motor by specifying the stator currents For simplification the considered motor has a single phase winding the operating principle being the same as that of the real motor provided with a three phase winding WWW ICpe ro icpe S A Splaiul Unirii 313 030138 Bucuresti RO 423140 J40 21438 92 tel O21 589 33 00 fax 021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 email Office icpe ro MKB NexteBank Energy service company Electrical engineering company Research institute for electrotechnics 0 90 160 2 0 360 9 Fig 3 2 1 Electromagnetic torque in case of a DC brushless motor The direction of the current through the winding is electronically reversed while passing from position 2 to position 3 of the rotor from position 4 to position 1 respectively The interaction between the rotor magnetic field and the stator current generates a torque which acts upon the conducting wires of the stator winding having the same direction in the positions 1 and 3 and in the positions 2 and 4 it is null It is obvious that the stator cannot rotate and in accordance with the principle of action and reaction there develops a counterclockwise torque over the rotor putting it into action The electromagnetic torque ripple is 100 being unusable in many industrial applications It is proved that if the
12. ric drives ICPE SA Department 4 ask the users for technical details concerning the application of these motors WWW ICpe ro icpe S A Splaiul Unirii 313 030138 Bucure ti RO 423140 J40 21438 92 tel 021 589 33 00 tax021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 nail Office icpe ro MKB NexteBank
13. single phase winding is replaced by a three phase one then the ripple decreases considerably Fig 3 2 2 shows brushless motors designed for the low power applications from the output of ICPE SA Department 4 WWW ICpe ro icpe S A Splaiul Unirii 313 030138 Bucure ti RO 423140 J40 21438 92 tel 021 589 33 00 fax 021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 email Office icpe ro MKB NexteBank Energy service company Electrical engineering company Research institute for electrotechnics Fig 3 2 2 Examples of brushless servomotors 4 Operating features In general the electric motors convert the electric power Pe characterized through the current J and voltage U into mechanical power Pmec charecterized through the rotational speed n and the mechanical torque M developed in the motor shaft The losses in the DC brushed brushless motors are of the type Py in the windings and losses in the magnetic circuit Pre which in general have reduced values 4 1 Electromechanical constant The geometrical design of the magnetic circuit and of the windings shows the way in which the motor converts the electric energy into mechanical energy The most important quantities are the speed constant kn and the torque constant ky Thus the speed constant represents the speed and the induced electromotive force Uina ratio and the torque constant represents the torque and the absorbed current ratio n knUina M kul the functions are
14. th the DC motor WWW ICpe ro icpe S A Splaiul Unirii 313 030138 Bucure ti RO 423140 J40 21438 92 tel O21 589 33 00 fax 021 589 34 34 RO40 CRDZ 024A 0863 9047 6001 email Office icpe ro MKB NexteBank Energy service company Electrical engineering company Research institute for electrotechnics ICPE Thus the DC servomotors differ from the DC classic motors in their oblong shape and the housing reduced diameter a design that offers a reduced inertia moment of the rotor fact that enables the increase of the useful torque necessary for the load acceleration Fig 3 1 4 Fig 3 1 4 Examples of DC brushed servomotors 3 2 Brushless electric motor In the case of these motors the commutator brushes subassembly mechanical inverter is replaced by an electronic inverter electronic commutation This design removes some disadvantages in comparison with the classic one represented by the maintenance increased costs due to the commutator brushes subassembly on the one hand and by the necessity of removing an important heat amount developed by the Joule effect in the rotor an area difficult to cool on the other hand The brushless motor efficiency is superior 85 90 compared to that of the brushed motors which is only 75 80 The brushless motor has the permanent magnets placed on the rotor surface and the winding is distributed to the stator lamination stack slots in this design the Joule losses are removed eas
15. w 4 6 Efficiency If the motor is supplied in the conditions under item 0 then the efficiency is defined by the following relation m My U Mr 30 000 Ussy n The maximum efficiency is calculated function the no load current Io the starting current Ip and is defined in the following relation I o mme f1 100 Yo 4 7 The heat time constant The heat time constant represents the time necessary for the motor temperature to reach 63 of the final operating temperature 4 8 Choosing the motor for accuracy drives The way of choosing a low power motor or a servomotor depends on the application for which it will be used and the criteria are the following e The mechanical time constant and the torque value requested by the drive e Angular acceleration e Load inertia moment e Intermittent regime Because of the fact that very often the application requirements do not comply with the motor rated characteristics in which cases the speed multipliers are necessary and all the drive mechanical parameters must be related to the motor shaft Other important factors Other important factors e Motor overall size e Operating environment temperature humidity explosion conditions shocks and vibrations etc e Maintenance period and costs e Efficiency Taking into consideration the complexity of the conditions with which these electric motors shall comply corresponding to the various types of elect
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