HIGH EFFICIENCY INTERNAL PERMANENT MAGNET SYNCHRONOUS ELECTRIC MACHINE
An internal permanent magnet synchronous electric machine has a rotor having a body of ferromagnetic material with a plurality of permanent magnets disposed wholly within the body and arranged in the body of the rotor as alternate North and South poles, each North and South pole formed by a pair of the permanent magnets arranged in a V with each magnet being a leg of the V with an apex of the V radially inwardly of ends of legs of the V so that each V opens outwardly in the body of the rotor at an obtuse electrical angle between the legs of the V of 135 degrees±one degree. The rotor has an outside diameter (Rotor OD) defined in terms of an outside diameter of a stator of the electric machine (Stator OD) as Rotor OD=Stator OD/(1.7±0.5%). Each North and South pole of the rotor has a pole-pitch to pole-arc ratio optimized for minimum cogging torque, maximum torque and optimized core loss.
1 . An internal permanent magnet synchronous electric machine, comprising:
a rotor having a body of ferromagnetic material with a plurality of permanent magnets disposed wholly within the body and arranged in the body of the rotor as alternate North and South poles, each North and South pole formed by a pair of the permanent magnets arranged in a V with each magnet being a leg of the V with an apex of the V radially inwardly of ends of legs of the V so that each V opens outwardly, each V having an electrical angle defined by an angle between the legs of the V that is an obtuse angle of 135 degrees±one degree;
a stator having a body of ferromagnetic material with a plurality of slots therein with conductive windings disposed in the slots;
the rotor having an outside diameter (Rotor OD) defined in terms of an outside diameter of the stator (Stator OD) as Rotor OD=Stator OD/(1.7±0.5%; and
each North and South pole of the rotor has a pole-pitch to pole-arc ratio defined by:
α
p
=
1
-
[
N
c
P
-
k
N
c
P
]
[
n
(
N
c
P
)
2
]
CPSR
where:
Nc=Least Common Multiple (Number of Stator Slots, Number of Poles)
P=Number of Poles
K=1, 2, 3, . . . .
Constant
Power
Speed
Ratio
CPSR
=
Maximum
Speed
Base
Speed
n=1 for CPSR=5 and n=0 for CPSR=2.
For CPSR values between 2 and 5, the n values are linearly interpolated between 1 and 0
n=0 for CPSR≦2 and n=1 for CPSR≧5
2 . The electric machine of claim 1 wherein the electric machine is a traction motor and the stator has an OD of 235 mm, a stack length of 93 mm, the rotor has an OD of 140 mm and the electric machine has a peak torque of at least 235 Nm, a peak power of at least 65 Kw, and an efficiency of greater than ninety-six percent around 8000 RPM.
3 . The electric machine of claim 2 wherein the magnets are neodymium iron boron magnets and a total mass of the magnets is no more than 0.85 kg.
4 . The electric machine of claim 3 wherein the total mass of the magnets is no more than approximately 0.75 kg.
5 . The electric machine of claim 1 wherein the electric machine is a traction motor/generator and the stator has an OD of 210 mm, a stack length of 60 mm, the rotor has an OD of 120 mm and the electric machine has a peak torque of at least 90 Nm, a peak power of at least 40 Kw, and an efficiency of greater than ninety-six percent around 6000 RPM.
6 . The electric machine of claim 5 wherein the magnets are neodymium iron boron magnets and a total mass of the magnets is no more than 0.6 kg.
7 . The electric machine of claim 6 wherein the total mass of the magnets is approximately 0.5 kg.