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Electricity
Extra-low voltage
three-phase motor
Ref :
302 189
n
S
=
g
ENGLISH
•
Line current I
•
The voltage
•
The total power consumed P
•
The rotational speed of the rotor n
•
The sliding g
For measuring the power, refer to the simulation performed on the extra-low
voltage three-phase terminal board.
To measure the rotational speed n of the rotor using the stroboscope:
increase the frequency of flashes; the rotational speed corresponds to the
largest frequency for which the reference frame is immobile.
Check that the star circuit is balanced: I
Check that the motor rotates slower in star connection.
Verify the relations:
I
Compare P measured with the value of P given by the relation:
Examples of results:
f
53
=
=
=
26
,
5
rps
p
2
−
n
n
S
n
S
Connection
I measured
Star
78 mA
Delta
171 mA
* The extra-low voltage wattmeter WJ2000 enables measurements only
between the neutral and phase. (star connection).
P
ϕ
cos
=
S
2 Single phase asynchronous motor
2.1 Objective
To measure the power consumed by a single-phase asynchronous motor.
or I
Υ
Δ
Υ
or g
.
Υ
Δ
≈ 0 A.
N
I
P
Δ
Δ
=
=
3
3
and
.
P
Υ
Υ
P = U × I ×
× cos
3
n
: rotational frequency of the rotating field
S
f : Frequency of the current
p : number of pole pairs
g : sliding
n
: rotational frequency of the rotating field
S
n : rotational frequency of the rotor
U measured
P measured
15.6 V
1.06 W
15.6 V
*
ϕ
cos
=
15
6
,
5
or P
Δ
or n
Υ
Δ
ϕ
.
n measured
1378 rpm
23 rps
1554 rpm
25.9 rps
1
,
06
≈ 0.50
× ,
×
0
078
3
g
13%
2%
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