Inverter VFD problem

I suppose it's just thermal management. You can get rid of the trips by turning down the deleceration parameter so it slows down more slowly. Rapid decel pushes up the DC link volts to a level that is too high and so the drives trips on OV.DC.

Does the fan go off? Might be a dodgy thermal sensor on the heatsink.

Rob.

lemelman wrote:

Thanks Rob, The fan does go off, eventually, but it can take a long time. It doesn't seem to have any untoward effects other than make an unwanted noise, but it surely indicates a fault somewhere. Do you have any further details on where to find the sensor 'cos I don't have any documentation?

Hiya, Sorry not, I don't nkow Siemens stuff, I used to design stuff for Control Techniques.

Be careful when you're messing with said thermocouple/thermistor because it can be tied to the hot side, and if you get it wrong at worst you'll blow it up and at worst you end up killing yourself.

Power electronics stuff is done differently to a lot of stuff, be warned.

Rob.

Who said anything about Siemens inverters?

Oh yeah it was a Mitsubishi....same applies.

Rob.

The cooling fan operation is set by Parameter #244. When that's set to 0, the fan should run all the time that Mains power is connected. If it's set to 1, the fan should only run when either:-

1. The motor is running (ie Inverter Run Command is invoked) OR
2. If the invereter is over temperature when the motor is stopped.

My 1.5kW Mitsubishi FR-E500-1.5K-EC Inverter, on a 6.5" centre lathe (#244 =3D 1), seems only to run the fan when the motor is on, so it's never been hot enough to invoke senario 2. Rob could be correct about your Thermal Sensor OR your unit could be performing as per design. Just because it doesn't feel hot doesn't mean to say that the heat- sink isn't at a temperature where the unit is set to operate the fan.

Of course, if #244 is set to 0, then you definitely have a problem.

Regards Andy

That's good advice. The heatsink can somewhat mislead. In my experience extruded alumninium heatsinks have a far better thermal conductivity than pressure cast alloy ones. If it's a cast heatsink then it might be substantially hotter under the IGBT/Rectifier pack. Most thermal models look at trends, or rather the rate of change of the temperature, such that the management software can say, 'hold on guys, they're pulling a a lot of current, turn the fans on'.

To be honest some thermal models are cleverer than others. On the drive I worked on, the thermal sensor was in the IGBT pack, and there was non in the rectifier pack. This was a 20hp/15kW drive and the semiconductor tech in those days was'nt man enough to get a 20hp solution in to a single pack.

What I had to do was to look at the magetising current in the inverter, because that would still create losses in the IGBT stack, but bugger all in the rectifier. You get high mag current when you're running the motor no load. Once you start asking the motor to begin supplying Torque, obviously the torque producing current part begins to climb which will then start to put up losses in the rectifier and so on. We all sorts of frig factors in there but it did work. We had to do it this way because one day I decided to abuse the driver by running at

12kHz and full load current...it did'nt take long for it to blow up because the management software had'nt been designed then.

Anyway I digress....sorry. Thought you might be interested.

Rob.

Talking of Mitsubishi inverters, are they likely to have an 'auto reset on power off' option? I've got a little one (Frequol, no idea of the model number) running a lathe coolant pump. It tends to trip if turned off & on again too quickly, which can happen inadvertently with my setup. It's buried at the back of the lathe, totally inaccessible at present so I have no coolant, it would be very handy to be able to set it for auto reset when I do get access. I've never been aware of this as an option before, but the Siemens I've put on my milling machine has it as default as well as a connection for an external reset button.

TimL

Tim,

I'm pretty certain you can do this. I've put a frequol manual up on my FTP site for you

Good luck

Bob

Bob, many thanks for that, I'll study it later.

Cheers Tim

As I mentioned in my first post, when initially installed the fan operated only when the motor was running. I haven't changed any parameters since then. Now, for the first few minutes or so after switching on, the fan runs only when the motor runs, but after using the lathe lightly it runs for quite a while (4 or minutes at least) when the motor is off. Towards the end of the 4/5 minutes, the fan switches off and on intermittently, sometimes staying off for several seconds before starting again. 10 of

15 minutes later, as long as I don't start the motor, the fan stops. As also mentioned, I can detect no rise in temperature anywhere on the case.