Question

compare between universal motor(AC series motor) and capacitor start motor

Wit! cont the 5. Compare your results from procedures 2, 3 and 4 with the results from procedures 2, 3 and 4 of Experiment 33. What conclusions can you make about the main winding currents? a. b. What conclusions can you make about the auxiliary winding currents? c. What conclusions can you make about the starting current for each type of motor? Curreut aud Curreut unike rsar motor has high Star ting arting Capacitar Start mohr has less tar Lleinc... C Start Motor matic Capacitor Start Motor he 5Compare these results with those found for the split-phase motor (Experi- ment 33). JU

Answer 1

(A) and (B):

Universal motors:

• When universal motor fed with AC supply, it still produces unidirectional torque.
• Because, armature winding and field winding are connected in series, they are in same phase. Hence, as polarity of AC changes periodically, the direction of current in armature and field winding reverses at the same time.
• Thus, direction of magnetic field and the direction of armature current reverses in such a way that the direction of force experienced by armature conductors remains same.

capacitor-start motor:

• I_M is the current in the main winding which is lagging the auxiliary current I_Aby 90 degrees
• to improve on the single coil design is by using an auxiliary coil in series with a motor starting capacitor.
• The auxiliary coilis used to create an initial rotating magnetic field.
• In order to create a rotating magnetic field, the current flowing through the main winding must be out of phase in respect to the current flowing through the auxiliary winding.
• The role of the starting capacitor is to lag the current in the auxiliary winding, bringing these two currents out of phase.
  
  Read more http://www.capacitorguide.com/motor-starting-capacitor/

(c) capacitor-start motor:

• it is their lower starting-torque that results in lower starting current. Because of the lower starting current,
• they are generally used for most single-phase applications between 3-and-10 horsepower due to their lower starting current.
• Common applications include: larger single-phase compressors, pumps, grinders, conveyors, and larger single-phase air-conditioning compressors.

Universal motors:

• Universal motors have series wound rotor circuitry similar to that of DC motors. They have high starting-torque and high-starting current. The name universal derives from the motor's capability of operating on either AC or DC power sources.
• Due to the inductive reactance of these windings the AC starting current will always be less than the DC starting current. Consequently, the starting torque on AC power will be lower than the starting torque on DC power.