DC electromagnet strong excitation fast pull-in circuit one a

In order to increase the attraction speed of DC electromagnet , strong excitation method can be adopted. The so-called strong excitation means
adding a higher excitation voltage to the coil when starting, usually 3 to 4 times the rated voltage. After starting is completed, the coil will switch to the rated excitation.
It should be noted that the strong excitation time (i.e. delay time) should be adjusted according to the actual situation, but it should not be too long, otherwise the electromagnet coil
will heat up or even burn out.
    The circuit is shown in Figure 6-31. This circuit uses a short-circuited resistor method to generate strong excitation . In the figure, KM is the control contactor
contact (the same below). The shortcoming of the circuit in Figure 6-31 (a) is that when the electromagnet YA is operating normally, the time relay
KT is also always working. If it is a relay or contactor (because they have normally closed auxiliary contacts), the circuit
wiring can be as shown in Figure 6-31 (b) . This can avoid the time relay KT - to participate in the work directly. In the figure, KMi is the control relay contact.