The work fulfillment order

1. To construct a scheme for the working characteristics removal (fig. 3.1 for laboratory work № 3). To startup the motor at the disconnected kit (switch "Switching of phases" must be in position "О").

After the motor acceleration to excite a generator to U =220 V, induction motor must be load , setting Rload at the circuit of armature of generator a current about 6А, and the readings of kit К-50 put in the table 6.1. Frequency of rotation is defined by the stroboscope method (laboratory work 3.2).

Table 6.1 - Investigations results of the unbalanced operations modes of induction motors

Type of induction motor	Winding connection	Working regime	Phases						n2
			IA	РА	IB	PB	IC	PC
			А	W	А	W	А	W	rpm
Short-circuited rotor		Symmetrical Syngle-phase
		Symmetrical Open delta
Phase rotor		Symmetrical Cutting of the phase wire

2. To move induction motor into single-phase mode, by opening knife-switch "Р" (fig. 6.1, а). Supporting the previous load, to put the readings of kit К-50 into the table 6.1, define rotor rotation frequency.

3. Winding of induction motor must be connected in delta. To carry out experiment in accordance with item 1.

4. To investigate the of the induction motor work with stator winding in the opened delta connection, for what a knife-switch of "Р" must be broken (fig. 6.1, b). Supporting the previous load, to put the readings of the kit К-50 in the table 6.1, to define frequency of rotor rotation.

5. To construct a scheme and perform the motor having a phase rotor startup (fig. 6.4). To perform induction motor load at symmetric resistance in the rotor winding (winding of rotor is short-circuited), to put the readings of the kit K-50 in the table 6.1; to define n₂.

6. To perform the phase cutting of rotor winding, measure currents in stator and to define n₂. To perform analogy measurements for the several values of motor load.

7. To perform the startup of the motor with open phase during different values of the staring rheostat, different velocity of the rheostat leading out. Obtain the steady motor operation if frequency of rotation is halved (point "b" in figure 6.5).

Control questions

1. Why is a starting torque in single-phase mode equal to zero?

2. How will power of the motor change during working a single-phase network if moment of resistance is mauntained?

3. Why does a motor continue to rotate during the linear wire cutting of the linear ware during motion?

4. Why is current beating arisen in stator during unbalanced resistances in the rotor circuit?

5. In what cases while the phase of rotor cutting of motor can develop frequency of rotation, equal to the 50% compared with rated frequency of rotation?