Modern High-Efficient PM Synchronous Motors

CUSTOM MADE CUSTOM PHILOSOPHY

Modern High-Efficient PM Synchronous Motors Recently developed projects

27.04.2016 – Hannover

Alessandro Sartorello

Introduction

» 3-ph PWM-inverter fed PM Synchronous Motors are widely used in automation and robotics due to their compactness and excellent dynamic behavior;

» Due to their high torque density, efficiency and power factor and the increasingly availability of modern electronic converters, PM Synchronous Motors are becoming an attractive choice in many industrial and civil applications;

» The variety of requirements and, recently, the concern for the cost and the supply of rare-earth magnets have pushed motor manufacturers to explore different topologies of PM Synchronous Motors.

Lafert Group

» Electric Motors manufacturer for more than 50 years

» Designing and engineering of customized electric motors to meet specific applications and needs of individual customers;

» Product range:

» AC Induction Motors IE2 and IE3

» High Performance PM Synchronous Motors IE4 and IE5

» Brushless Servo Motors for AC Drives

» Gearless PM Synchronous Lift Motors

» Sales revenues 2015: 139M €; 50% of them are from Synchronous Motors;

» Number of employees: 730;

» Yearly production of about 1M motors;

» Manufacturing in Italy, Slovenia and China.

Surface Mounted PM Synchronous Motors

Surface mounted PM Synchronous Motors (SPM) with precise position sensors represent the state of the art for high performance AC drives.

They have high energy magnets glued on the rotor surface, providing:

» High efficiency and power factor;

» High torque density for reduced weight and volume;

» High peak torque and low rotor inertia for fast accelerations.

Typical applications are: robotics, packaging, textile machines, machine tools, factory automation.

Lafert produces an extended range of brushless servomotors for Motion Control applications, with output stall torque from 0.20 up to 390 Nm.

Customized Servo Motor for extreme dynamics

» SPM motors are the ideal solutions to satisfy the high dynamics demand, with:

» Small rotor diameter;

» Rare-earth magnets with the highest flux density available;

» Minimized parasitic losses in rapid transients (optimized winding, stranded conductors, magnet segmentation);

» Efficient cooling system for high torque density, thanks to potted winding and oil channels in the housing.

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Torque/speed characteristic

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» high speed (>10000rpm);

» high peak torque (>13Nm) over a wide speed range (up to 10000rpm);

» extremely low inertia (<0.4 kgcm2) and fast accelerations (>325000 rad/s2);

» low energy consumption during the work cycle;

» compactness;

Compact Servo Motors

» Outstanding torque density SPM motor can be realized using:

» concentrated non-overlapping winding (short winding overhangs);

» potted winding with high thermal conductive epoxy resins;

» strong rare-earth magnets;

» low losses electrical steels.

Compact Servo Motors

B56Q New B40J

Square 91 80

Rated speed rpm 6000 6000

Stall torque Nm 3.5 3.5

Rated torque Nm 2.0 2.6

Stack length % 100 75

Motor length % 100 65

New series of extremely compact PM synchronous motors have been developed:

B20J, B30J, B40J, B90J with a shorter total motor length with respect to the existing series.

IE5 SPM Rare-Earth Synchronous Motors

» IE5 efficiency level: top efficiency class according to IEC 60034-30-1;

» Losses reduced by 20% compared to IE4 motors;

» Designed for pumps, fans, compressors;

» PM synchronous motor with a TEFC construction with no position sensor;

(frame sizes dimensions according to EN 50347 );

» Robust and reliable construction, suitable for sensorless control;

» Wide power (0.55->30 kW) and frame ranges (from 71 to 160);

» Reduced frame compared to the output power (very compact design).

PM Synchronous vs Induction Motor

IE2 AMHE 160 Induction

IE5 HPS 112 PM

Power kW 15 15

Speed rpm 2948 3000

Torque Nm 49 48

Voltage Vrms 400 380

Current Arms 28 24

Power factor 0,85 0,99

Efficiency % 91,4 94,5

Total losses W 1408 870

Copper losses W 449 435

No-load losses W 574 355

Slip losses W 267 0

Stray-load losses W 118 80 => Smaller motors with higher efficiency

PM assisted Synchronous Reluctance Motor (P.M.A.S.R Motor)

» The torque is the sum of 2 terms: magnet torque and reluctance torque;

» In P.M.A.S.R. the reluctance torque is maximized thanks to:

» low poles number (ie: 4) » multiple flux barriers design; » reduced airgap; » rotor bridges with reduced thickness and saturated by magnet flux.

» The magnet torque is 10-20% of the total torque

=> a reduction of the magnet quantity or utilizing ferrite is possible;

» Effective flux-weakening and wide constant power region (1:6 as base speed/maximum speed ratio);

» High efficiency even at light load and low speed (load dependent core losses);

» Suitable for high speeds (> 4000 rpm), if the rotor bridges are properly sized;

» Ideal for zero-speed sensorless control (with an high frequency signal injection for detecting the rotor anisotropy).

PM assisted Synchronous Reluctance Motor (P.M.A.S.R Motor)

Main disadvantages:

» Non linear and core saturation dependent torque-current relationship:

=> complex torque control algorithm (adjusted to the particular magnetic design);

» Lower torque density with respect to SPM motor;

» Torque ripple and acoustic noise can be a concern;

» Not suitable for concentrated non-overlapping windings (harmonics);

Spoke-type Interior PM Synchronous Motor

» Flux-focusing configuration:

» increased air-gap flux density in comparison with a SPM, with the same magnet Br;

» Simplified magnet shape;

» Reduced rotor anisotropy if the rotor shape is properly designed:

=> it can be driven by the same available control algorithms (sensored or sensorless) of SPM motors.

1) ferrite magnets;

2) excellent torque density using rare-earth magnets;

IE4 IPM Ferrite Synchronous Motor

Innovative concentrated winding design for optimized harmonic content to

reduce the harmonic fields effect such as losses, noise and vibrations.

» IE4 efficiency level;

» Inexpensive ferrite magnets with interior PM “Spoke” rotor configuration;

» Robust TEFC construction with no position sensor (frame sizes dimensions according to EN 50347), suitable for sensorless control;

» Same reduced frame sizes of IE5 SPM rare-earth PM motors for a given output power;

» Concentrated non-overlapping winding: short winding overhangs and reduced copper losses, robust insulation and high productivity.

Extremely Compact Brushless Servo Motors

» Suitable for robotics and machine tools;

» High performance NdFeB magnets with IPM “Spoke” rotor configuration;

» Stack length reduced by about 20% if compared to a SPM configuration;

» Outstanding compact motors if combined with concentrated non-overlapping winding, separate-teeth and potting technologies;

» Middle-high inertia;

Extremely Compact Brushless Servo Motors

SPM IPM

spoke type

Voltage Vrms 400 400

Rated speed rpm 3000 3000

Stall torque Nm 28 28

Rated torque Nm 20 20

Peak torque Nm 85 85

Peak current Arms 65 76

Stack length % 100 75

Motor length % 100 85

Active material cost % 100 90

=> Shorter motors with higher performances

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Tmax SPM S1 torque SPM

Tmax IPM S1 torque IPM

Thanks for Your attention

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