Environmental Engineering Reference
In-Depth Information
single and multilayer chevron shaped buried magnet (IPM) designs. The industrial
motors are all rated 75 hp (56 kW), 400 V with class H insulation (180
C) or
125
C temperature rise in a 55
C environment (Table 5.9). What these authors
find is very relevant to the theme of this text:
IM NEMA 250 frame TEFC (totally enclosed fan cooled), 4-pole and 60 Hz
base frequency
●
SPM machine, same size as the IM, but wound for 8-pole, 120 Hz base
frequency, fan cooled
●
Salient pole design using same stator as the IM, but different winding as 4-pole
and fan cooled
●
Table 5.9 Industrial motor comparison, 75 hp (56 kW) tested at full
load, 1,800 rpm
Attribute
Unit
IM
SPM
IPM
Number of poles
#
4
8
4
Voltage*
V
459
405
395
Base frequency
Hz
60
120
60
Torque
Nm
304
298
298
Current*
A
92
85
90
Power factor
#
82
98
93
Efficiency
%
93.6
96.2
96.8
Temperature rise
C
111
71
90
*Voltage and current are rms values, line-to-line and line respectively.
For the same shaft power (~56 kW), the SPM runs the coolest, has the best
power factor, lowest line current and high efficiency. The IPM comes in second and
lowest in the performance category is the IM.
Dynamic performance is a particular requirement, especially for the generator,
MG2, in an eCVT hybrid vehicle. Typically, in hybrid vehicle systems, the con-
troller must incorporate inertia compensation to correct for generator rotor inertia.
In a detailed analysis, these rotating component inertias can be reflected to the drive
wheels and contribute to higher inertial mass to be accelerated. Polar moment of
inertia is given as (5.40)
J
0
¼
M
rot
r
ro
ð
5
:
40
Þ
Initial acceleration of an electric machine commanded to peak torque is strictly
dependent on its polar inertia:
m
¼
J
0
w ¼
J
0
a
ð
5
:
41
Þ
