8) This describes the essential skills and knowledge and their level, required for this unit. Evidence shall show that knowledge has been acquired of safe working practices and rewinding direct current machines rated for low voltage. All knowledge and skills detailed in this unit should be contextualised to current industry practices and technologies. KS01-EG154A Direct current motor winding techniques Evidence shall show an understanding of direct current motor winding techniques to an extent indicated by the following aspects: T1 Principles and construction encompassing: Direct-current machine types Construction of direct-current machine Types of armature windings Parallel circuits in armature windings Value of generated e.m.f. T2 Direct current armature windings encompassing: Terms used in armature winding Lap and wave windings Progressive and retrogressive windings. T3 Simplex lap windings encompassing: Simplex lap armature winding Commutator pitch Number and position of brushes Characteristics of simplex lap windings Equalising connections for armature windings Applications for lap windings. T4 Simplex wave windings encompassing: Simplex wave armature winding Commutator pitch Number and position of brushes Dummy coils Characteristics of simplex wave windings Applications of wave windings Comparison of lap and wave windings Armature winding calculations. T5 Commutation and interpoles encompassing: Principles of commutation Conditions for sparkless commutation Methods used to reduce sparking Resistance commutation e.m.f. commutation Interpoles or commutating poles Advantages of interpoles. T6 Testing techniques encompassing: Continuity Insulation testing Use of ‘growler’ Magnetic field testing T7 Critical details and measurements when stripping a stator of a DC machine. Types of windings. Wave winding. Lap winding with equalisers Winding layout. T8 Procedures and precautions required when inspecting and/or re-using a commutator Removal of armature leads on TIG welded commutator. Dimensioned to be checked. TIG Welded and soft soldered commutators. Coil position and commutator segment relationship. Commutator wear ring. T9 Preparation for rewinding. Checking the condition of a: Stripped core. Commutator. Removing of old winding. Core loss test. Hot spots in armature core. Testing commutator before use. T10 Selection of appropriate insulation. Reason for selecting a particular insulation. Dielectric strength. Temperature rating. Manufactures recommendations. Standards. Insulation properties, method of application and specific uses for: B stage insulation VPI insulation Insulations used on the slot portion and overhang. T11 Calculations and insulation specifications. Preparation of coils and equalisers. Manufactures specifications. Calculation of a half coil length and the amount of copper required. Preparation of copper prior to insulating coils and equalisers on armatures; Commutators. TIG welded. Soft soldered. Identification of insulation specifications. |