Jogging and inching:Inching Controls

Inching Controls

As stated previously, jogging and inching are very similar in that both are accomplished by providing short jabs of power to a motor to help position certain pieces of machinery. Inching, however, is accomplished by providing a reduced amount of power to the motor. Transformers can be used to reduce the amount of volt- age applied to the motor during inching, or reactors or resistors can be connected in series with the motor to reduce the current supplied by the power line. In the circuit shown in Figure 30 – 7, resistors are connected in series with the motor during inching. Notice that inching control requires the use of a separate contactor because the power supplied to the motor must be sepa- rate from full line voltage.

Review Questions

1. Explain the difference between inching and jogging.

2. What is the main purpose of jogging?

3. Refer to the circuit shown in Figure 30 – 8. In this circuit, the jog button has been connected incorrectly. The normally closed section has been connected in parallel with the run push button, and the normally open section has been connected in series with the holding contacts. Explain how this circuit operates.

4. Refer to the circuit shown in Figure 30 – 9. In this circuit, the jog push button has again been connected incorrectly. The normally closed section

of the button has been connected in series with the normally open run push button, and the normally open section of the jog button is connecting in parallel with the holding contacts. Explain how this circuit operates.