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When it comes to motor controls, jogging is a method that uses short bursts of power in order to move a motor or a load into a needed or desired position. NEMA defines jogging as “the quickly repeated closure of a circuit to start a motor from rest for the purpose of accomplishing small movements of the driven machine.”
There are multiple circuits and methods for achieving a proper jog in a motor control circuit. In all of these methods the object is to interrupt the holding contact from the start stop buttons to prevent the sealing of the hold circuit to the motor starter coil.
In this episode of Basic Motor Controls: Jogging Circuit at #accesstopower, we go over three different circuits and methods for achieving a proper jogging circuit. Follow along as we demonstrate how each of these circuits work.
Circuit #1 is accomplished with a 2 position selector switch which is used to break the holding contact to the starter coil. With the contacts from the selector switch open, the start button is then used as a momentary jog button. The selector switch contacts must then be returned to the closed position for the start stop circuit to work properly once again.
Circuit #2 demonstrates a jogging circuit using a double acting push button. This button is used to simultaneously open the holding circuit by opening a normally closed circuit and, at the same time, closing a normally open circuit to send power to the coil. This leaves the start button to be used as a start button only and the separate double acting push button is used for the jog circuit exclusively.
Finally in circuit #3 we use an 8 pin ice cube relay to control the start of the motor. This is accomplished by using the two normally open contacts in the relay. The first NO contact is used as a holding contact for the relay itself, while the second NO contact is used to energize the motor starter coil. A NO jog push button is used in parallel to the second relay NO contact to energize the motor starter coil directly. If the relay is off, the motor can be jogged by the jog push button. When the relay is energized the motor starts and runs normally.
There are many other ways to accomplish a jogging circuit, but every single method will involve the breaking of the holding contact in order to achieve the momentary burst of power needed to jog the starter.
Check out the video for a tutorial on all 3 of these jogging circuits.