Meddings Pillar Drill, VFD and referb

The VFD works fine when the motor is not connected. As soon as i connect it and power on the VFD it immediately trips the fuse.

i have checked to motor winding etc and all is fine, plus the motor was working fine before i /bought it, connected to 3 phase supply.

looking at the wiring under the motor over, where the supply enters, it looks like its setup in a star config.

any thoughts?

Edited By petro1head on 06/12/2019 13:13:03

Are you working on 240 or 415 volts?

Can you clarify what you mean by 'connected' and 'connect' in the first sentence. (ie it worked when connected, but not when you?)

Ian P

240V

I have aditied the first post and added Not

Also what do you mean by ‘trips the fuse’. Fuses ‘blow’. MCBs trip and can be reset. Is this the mains supply or just the local plug-top fuse? Does the VFD run without the motor connected? Are you switching on the supply to the VFD with it programmed to start the motor at switch-on ( not a good idea)? Are you using the machine switch, not the VFD start button?

Sorry, yes trip the MCB

VFD works fine without the motor connected

The motor is connetcted directly to the VFD, no switch, so I just power the VFD on

This is the VFD I am using VFD

A photo of the motor plate & connection box wiring layout would help someone determine or at least point to any obvious errors.

Make/model of VFD ?

By "VFD working fine" do you mean it just powers up or have you tested it for output.

Have you set up the VFD to match the motor specs ?

regards

Too much inrush current for the MCB? Set the VFD for soft start.

Can you confirm if it is a fuse rupturing or an mcb tripping, also state size and type.

The rating of the fuse or mcb could be too low for the load or the motor may have an line to earth fault.

If supply is 240v to the VFD you will as a rule be getting 220v 3 phase output so your motor needs to be connected in Delta form for the lower voltage to function at rated power.

Emgee

See previous post for VFD Make/Model

Not tested for output

Setup, hmm good question. Just using using default settings. Oh god I can hear you swearing at me now

Edited By petro1head on 06/12/2019 13:44:53

MCB

Well done, sorted.  Now wired in Delta config and working thanks

Edited By petro1head on 06/12/2019 14:01:30

Although all cable ID's are shrouded I agree looks like connected for 400v working, remove links and fit top to bottom as pictured.

What rating and type is the mcb ?

Emgee

See above

To be honest a bit confused by Star vs Delta

Is that motor dual voltage ? Cannot see lower voltage on the plate. Correct me if I am wrong.

Just 410

Oh. Check your speeds as it will only probably run at 2/3 speed on 230v and will probably stall if any load is applied.

Extract from Inverter drive website. The motor must now be considered as a 230V x 29Hz motor as far as data entry into the Inverter Drive is concerned. The Full Load Current will be that stated on the nameplate for 400V.

If the maximum speed is set to 50Hz or more, the Motor may possibly reach these speeds, but it will become progressively "Under-Fluxed" (Torque will reduce). However, this will only be evident if the Motor is fully loaded. If it is, the Motor will look for more current to meet the load. A correctly set Inverter will provide protection against over-Current by reducing the speed automatically to bring the load current under the maximum set.

It is important to note that when the Inverter output voltage does not match the Motor rated voltage, the drive should match or exceed the Motor full load current (not kW).

The link to your inverter is blocked by my malware software so could not check it out. You will need to really study your VFD settings to get much use out of that motor.

I hope this has not put the cat amongst the pigeons.

regards

Edited By Oldiron on 06/12/2019 14:31:16

Indeed it has, but the pigeons are mobbing the cat.

The speed of an induction motor is determined mainly by the applied frequency, and to a much smaller extent by the load. The speed is unaffected by the motor being connected in star or delta. However, if you apply 240V to a motor in star, and designed to run at 415V, then the phase currents will be lower. In theory the currents will be lower by the square root of 3. To a first approximation the torque of an induction motor is proportional to phase current. Power is torque times angular velocity. So for a motor connected in star, but running at 240V instead of 415V, the angular velocity will be the same, but the torque, and hence power, will be reduced by a factor of root 3.

Summary: The motor should run fine on 240V, but the available torque and power will be reduced.

Andrew

Try this link which is now public in my Google Drive VFD Manual

Star or delta connection should not have a bearing on the fault you were getting, but I see evidence of burning to the right of the connector block. I don't think that you can safely assume that this fault is fixed.