# Mitsubishi Vfd - Wiring



## bigmojo (Dec 11, 2015)

Wiring up the Mit 720 VFD and have a question re: start/stop function via momentary buttons.  Based on the info below, combined with the fact that i am using source logic rather than sink logic, am i right in thinking that i would disconnect the short from S1 to SC and use S1 as the STOP, and therefore wire as follows:


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## mksj (Dec 12, 2015)

The schematic looks correct for 3 wire momentary, but there may be a problem. Using the JOG terminal by itself, sets the frequency and JOG acceleration/deceleration. STF and STR are needed to turn on the rotation. My concern with the 3 wire and JOG as drawn, is that what happens after you release the JOG button. Since there is no STOP interrupt (s1 holding is on), then the motor would resume its speed to the STF/STR set point because S1 has not been interrupted. Releasing the JOG button/command does not issue a STOP/interrupt command by my read of  the manual, which is very hard to follow with referrals to pages all over the place.  When S1 is active, the STF or STR is held on once you release the momentary direction switch. *Now the manual states that when JOG input is active (RL must be programmed to this function), the stop signal is deactivated. So in theory your schematic may work, just add a momentary stop switch. *

So the schematic you have drawn for 3 wire would need an E-STOP and a separate momentary stop switch for the Forward Reverse stop after that.

If there is a problem in the JOG not shutting off and to run a JOG command and not have it connected to the sustain S1, it may need to be inactivated when jogging. To do this you would need a JOG switch with a NC and a NO contact block. The output from your E-Stop goes to the input of both switch blocks (parallel). The NC output contact then connects to the NC momentary stop switch. The other NO JOG switch output connects to RL and the direction switch, followed by the diodes as drawn. Under normal operation the JOG circuit is disconnected. When you press the JOG button it disconnects S1 (holding) and RL and STR or STF is operated without holding. This assumes the switches are break before you make (no switch overlap, i.e. STR/STF is disconnected before S1 is reconnected). On VFDs, sometimes you just need to wire them up and play with the program parameter controls. This is easy enough to test out with switches before everything is mounted and finalized, so try your schematic first, and if needed just add another contact block to your jog switch. 

I have done 3 wire control with latching relays and an interlock system, but this should be doable without that. Lots of different ways to do this, but it is one reason I like to build new design systems and test them before posting.

I feel like I am on stump the chump.

Hope this works for you.
Mark


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## bigmojo (Dec 12, 2015)

Mark, sorry for rehashing what should be a closed issue.  I figured i would try to make this as difficult as possible. ;-)

As always - Thank You for the direction and explanation.


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