The various starting methods are best described with the aid of circuit diagrams showing how a motor is connected to the electricity supply. The following drawings show only the stop, start and power switching for clarity, they do not show the motor or starter protection systems or safety systems or control or alarm or indication systems.
Later in this article control cable capacitance is discussed together with the use of pilot contactors to minimise the effects of that cable capacitance; however in the following drawings pilot contactors are not shown again this is for clarity and to allow an easier understanding of the circuits.
All the drawings show the motor connections for clockwise rotation or for reversing motors clockwise rotation for the forward direction.
The drawings for the various starting methods for single direction motors each have a main contactor this is deliberate. Where additional contactors are required for the particular starting method these are additional to the main contactor.
By using a main contactor in each of the starting methods for single direction motors it is relatively simple to introduce a second contactor in parallel with the main contactor with the phase connections altered in line with the drawings shown in the section 02.09.14.00 entitled motor windings and terminals, for bi-directional motors. However to maintain the correct connections for reversing star delta starting and to minimise the current peak when changing from star to delta an additional contactor is required to be placed in the delta circuit.
The drawings for single speed motors, both single and bi-directional, can again be easily adapted for multispeed motors with either single or dual tapped windings or multi-winding motors or combinations of the two.