Mitsubishi Inverter fault diagnosis

[Kevin McCartneyParticipant @kevinmccartney]

Hi

Wondering if anyone can help diagnose a problem with my inverter. It is a Mitsubishi E500 and has worked flawlessly for 10 years or so. I have it connected to a large 4 pin socket so that I can swap it between my lathe and mill.

It now only works very intermittently. When I power it on fans start as they always have with 0.00Hz on the display. When I lift the lever to start either machine the motor buzzes loudly the hertz figure increases but the motor doesn't start. If left buzzing it will "trip" and show OL on the display. This behaviour is replicated when connected to either the lathe or mill which makes me think I can rule out the machine motors as being faulty. Nothing has been disturbed or changed recently.

There are two links below to short clips of the motor noise and the inverter display.

Any assistance would be appreciated, thank you.

Kevin

[Kevin McCartneyParticipant @kevinmccartney]

[SillyOldDufferModerator @sillyoldduffer]

Page 183 of the manual says:

The running frequency has fallen to 0 by stall prevention

activated. (OL while stall prevention is being activated.)

 

As the motors aren't starting I suspect a cable fault or loose connection that's failing to deliver one of the three phases.

 

The motor not starting on two phases seems consistent with the VFD detecting a stall, and refusing to power the motor (0.0Hz), Unless both motors have jammed! – Unlikely.

 

Check the output connections on the VFD – all three phase wires must be connected firmly to their terminals.

 

Then check the switch-over socket. All three females must be a tight fit to a plug, also ensure all 3 phase cables are connected to their female and the terminal screws are tight.

 

If it's a dangling socket, the terminal connections could be stressed every time the motors are swapped. If all good inside the socket, it's possible one of the 3 cables has fractured somewhere inside the insulation and gone intermittent. Usually happens near the point of maximum flexing near plugs, sockets and bulkheads. If flexing is likely in the set-up, probably best to replace the whole cable between VFD and socket.

 

Testing continuity with an analogue multimeter can save a lot of time, especially with intermittent breaks – watch for the needle flicking, whilst an assistant brutally flexes the cable from end to end.

 

Dave

 

 

 

 

[Kevin McCartneyParticipant @kevinmccartney]

Dave

Thanks for taking the time to reply. I have checked all terminal connections and they're tight. The switch over socket is wall mounted. I have rattled, pulled and twisted the cable between the VFD and socket but the symptoms are the same. I haven't tried the multimeter yet but will next weekend.

Since your reply another fault code has appeared on the E500 – E.LF but only when connected to the lathe! This is an open circuit on phase U.V.W load side.

I'm wondering if I have two gremlins – a faulty motor on the lathe and an intermittent fault in the switch box (on/off switch or speed potentiometer) for the VFD?

Kevin

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