Exercices Corrigés Machines à Courant Alternatif Électromécanique des Systèmes Automatisées-ESA-OFPPT-PDF
Exercices Corrigés Machines à Courant Alternatif
ESA-OFPPT-PDF |
Data
An
asynchronous ring motor has the following characteristics: 95 kW; 230V / 400V;
50 Hz; 8 poles.
1) Knowing
that it is powered by a three-phase 400V line, what should be the coupling?
2) Calculate
the synchronism frequency.
When running,
the slip is worth 4%:
3) Deduce the
frequency of rotation.
4) What is
then the value of the useful torque.
The motor is
very powerful, we can neglect its stator and mechanical losses. For nominal
speed:
5) Calculate
the electrical power absorbed.
6) Calculate
the intensity of the current absorbed by the stator if the power factor is
0.83.
We now supply
the motor with a 230 V line.
7) What is
the coupling of the stator?
8) Calculate
the effective value of the current intensity in the line.
9) Calculate
the effective value of the current intensity in a winding.
Answers: 1 /
star 2 / 750rpm 3 / 720rpm 4 / 1260Nm 5 / 98958W 6 / 172A 7 / triangle 8 / 298A
9 / 172A.
An
asynchronous star-coupled motor carries the following indications 220V / 380V:
No load: Io =
5.2 A Po = 390 W
On load: I =
7.5 A P = 4070 W
The
resistance between two phases of the stator was measured hot R = 2.2 W.
Assuming that
the mechanical and magnetic losses are equal, calculate the motor efficiency if
the frequency
rotation is
1430 rpm.
Answers: 0.83
An
asynchronous motor is such that:
When empty,
its frequency of rotation is close to synchronism.
In load, its
mechanical characteristic is practically straight.
In nominal
operation, the following have been determined: Pa = 3.4 kW; Ș = 86.5%; n ’=
1440 rpm
Calculate the
synchronism frequency and the number of poles.
1) Calculate
the moment of the useful torque.
2) Give the
equation of the mechanical characteristic in its useful part.
3) In reduced
load operation, the slip is 2.67%.
4) Give the
frequency of rotation.
5) Determine
the useful torque and the useful power.
6) The
resistive torque of the driven machine takes the value of 22 Nm. Calculate the
slip.
Answers: 1 /
1500rpm 4 poles 2 / 19.5Nm 3 / Cu = -0.325 n ’+ 487.58 4 / 1460rpm 5 / 13Nm
1432rpm 6/5,
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