# Energy-efficient magnet-free Synchronous Reluctance Motors

More than 60% of electric energy in industry is consumed by induction motors. The efficiency of the induction motors is low due to high rotor losses. Company EMACH has developed efficient magnet-free synchronous reluctance motor (SynRM) which efficiency significantly exceeds efficiency of induction motors as well as of other motors.The results of the experimental comparison of the SynRM developed by the company EMACH and motors of other manufacturers are presented below.

The EMACH’s SynRM has lower manufacturing cost due to absence of squirrel cage and has 2.5 kg (19 %) lower weight than ABB’s induction motor. Also EMACH’s SynRM production cost is much lower than Hyosung’s motor with magnets production cost due to absence of magnets in SynRM design.

** Table 1. Characteristics of 1500 W 3000 rpm motors**

Motor type |
Induction motor |
Magnet-free SynRM |
Motor with magnets |
Magnet-free SynRM |

Manufacturer |
ABB |
ABB |
Hyosung |
EMACH |

Rated efficiency, % |
84 |
87.9 |
89.3 |
90.7 |

Efficiency class (Old standard IEC 60034-30-1) |
IE3 |
IE4 |
Much higher than IE4 |
Much higher than IE4 |

Weight, kg |
15.5 |
13 |
7.5 |
13 |

The IE efficiency class levels of 1500 W, 3000 rpm motors according to the old standard IEC 60034-30-1 are as follows: IE1=77.2 %, IE2=81.3 %, IE3=84.2 %, IE4=86.5 %. The rated efficiency of the EMACH’s SynRM is much higher than rated efficiency of the ABB’s and Hyosung’s motors and much higher than efficiency of IE4 class level.

Figure shows the experimental comparison of the EMACH’s SynRM (green line) with the ABB’s induction motor (blue line), ABB’s SynRM (purple line) and Hyosung’s motor with magnets (red line) at the pump load (quadric dependence of torque on speed). It is seen that the EMACH’s SynRM efficiency is much higher than the ABB’s motors efficiencies and higher than Hyosung’s motor with magnets efficiency in wide range of speed and power.

The Standard IEC 60034-30-1 «Rotating electrical machines – Part 30-1: Efficiency classes of line operated AC motors (IE code)» sets levels of efficiency classes for induction motors powered directly from the electrical network. Therefore, it would be incorrect to apply the Standard IEC 60034-30-1 efficiency classes for labeling the motors powered by the frequency converter. However, leading manufacturers (for example KSB, Hyosung et al) subsume their motors powered by the frequency converter according to the Standard 60034-30-1.

Now, in 2016 the new standard IEC 60034-30-2 «Rotating electrical machines – Part 30-2: Efficiency classes of variable speed AC motors (IE-code)» is developing. In this new standard the IE energy efficiency classes for the motors powered by the frequency converter will be set. According to the new standard IEC 60034-30-2 for the pumps and fans, the total efficiency Eff_{total} of the motor should be determined according to the formula:

Eff_{total}=(Eff_{1}+Eff_{2}+Eff_{3} )*0.33 (1)

where Eff_{1} is the efficiency at the rated speed and torque, Eff_{2} is the efficiency at the speed equal to 75% of the rated speed and the torque equal to 50% of the rated torque, Eff_{3 }is the efficiency at the speed equal to 50% of the rated speed and the torque equal to 25% of the rated torque.

After finding the total efficiency by the formula (1) according to the new standard IEC 60034-30-2, the IE energy efficiency class of the motor, powered by the frequency converter can be qualified. The achievement of the high total efficiency by the motors according to the new standard IEC 60034-30-2 is complicated by the necessity to provide not only the high efficiency at rated speed and torque, but also during the operation under low-load conditions. Additionally, levels of the energy efficiency in classes IE3 and IE4 according to the new standard IEC 60034-30-2 are much higher than the same levels according to the old standard IEC 60034-30-1. Thus, for 1500 W motors the IE class levels according to the new standard IEC 60034-30-2 are as follows: IE1=77.2 %, IE2=82.8%, IE3=85.3%, IE4=88.2 %.

The expected efficiency of IE5 class level is 90.2 %. EMACH’s magnet-free SynRM, ABB’s induction motor, ABB’s SynRM and Hyosung’s motor with magnets were tested in accordance with the new standard IEC 60034-30-2; the results are given in the Table 2.

**Table 2. Experimental comparison of motors according to standard IEC 60034-30-2**

Motor type |
Induction motor |
Magnet-free SynRM |
Motor with magnets |
Magnet-free SynRM |

Manufacturer |
ABB |
ABB |
Hyosung |
EMACH |

Eff |
84 |
87.9 |
89.3 |
90.7 |

Eff |
83.5 |
84.3 |
86.9 |
90.5 |

Eff |
75.4 |
79.1 |
78.5 |
90.2 |

Eff |
80.2 |
82.9 |
84.1 |
89.6 |

Efficiency class (New standard IEC 60034-30-2) |
IE1 |
IE2 |
IE2 |
IE4 |

Thus, according to new standard IEC 60034-30-2, the efficiency of tested ABB’s induction motor in pump-type applications corresponds to the efficiency class IE1. The ABB’s SynRM and Hyosung’s motor with magnets meet the requirements for the efficiency class IE2. The SynRM manufactured by EMACH meets the requirements for the efficiency class IE4.

The magnet-free SynRM technology developed by EMAСH is protected by the patent.

The magnet-free SynRMs can replace the induction or permanent magnet synchronous motors and can be applied in variable speed applications such as pumps, fans, compressors, extruders, conveyors, mixers and other typical applications.