We have a very noise sensitive application, and need to supply the motor with a relatively clean current. The motors we need
to use are the Etel TMM 210-30-3TAS, and TMM 210-050-3TAS. We have been given the component values for the filter we
selected, they are summarized below. To simplify the analysis of the filter circuit the line to neutral values will be used. Motor
inductance, and amplifier limits changed to line to neutral. I know that this circuit is an oversimplification, and lacks the loss
and self resonant frequency components of the filter inductor, and motor, and cable capacitance.
Filter
Motor
L1
3.0mH
C1
L2
17.14mH
9.23uF
R1
2.9
R2
3.73
Lf := 3.0⋅ mH
Cf := 9.23⋅ µF
Rf := 2.9⋅ Ω
Lm :=
29.7
⋅ mH
3
Lm = 17.147 mH
Rm :=
6.46
⋅Ω
3
Rm = 3.73 Ω
The impedance looking into the filter with the motor attached is:
1
⎤
⎤
⎡⎡
⎢ ⎢ ⎡i⋅ 2⋅ π ⋅ f ⋅ C ⎤ + Rf⎥ ⋅ ⎡⎣i⋅ ( 2⋅ π ⋅ fop) ⋅ Lm + Rm⎤⎦ ⎥
op) f⎦
⎣⎣⎣ (
⎦
⎦
Zin( fop) := ⎡i⋅ ( 2⋅ π ⋅ fop) ⋅ Lf⎤ +
⎣
⎦ ⎡
1
⎤
⎢ ⎡i⋅ 2⋅ π ⋅ f ⋅ C ⎤ + Rf⎥ + ⎡⎣i⋅ ( 2⋅ π ⋅ fop) ⋅ Lm + Rm⎤⎦
op) f⎦
⎣⎣ (
⎦
The inductance limits on the amplifier are:
( )
(
)
15
( )
(
)
2.5
ZLX fop := i⋅ 2⋅ π ⋅ fop ⋅
ZLL fop := i⋅ 2⋅ π ⋅ fop ⋅
⋅ mH
3
⋅ mH
3
The following graph shows the impedance verses frequency that the amplifier "sees". The amplifier allowed
inductance impedance limits are also shown on the graph, and it can be seen that the filter + motor impedance is
within them at both the 8 KHz, and 16 KHz switching frequencies.
1 .10
4
1 .10
( )
ZLL( fop)
Zin fop
( )
ZLX fop
3
100
10
1
0.1
10
100
1 .10
fop
3
1 .10
4
1 .10
5