connection and operation of dual volt and dual hz rated motor on an inverter

[jim gage]

I am currently trying to find out if I should connect a motor in delta or wye.
The motor name plate states 400v 50 hz 48.5 amp and 480v 48.5 amp 60 hz
it is powered by a Berges inverter. This is a radial rock saw and they had lost 3 motors before I was called.
I would like to make sure I get this right to avoid another problem.

 

[jim gage]

I am unable to contact the motor manufacturer in Italy and all research I find tells me to connect the low voltage name plate rating in delta and the high volt name plate rating in wye but my customer says they are sure it arrived on site originally in delta and this has me cautious due to their run of failure of this motor.

 

[winnie]

In general for IEC motors the low voltage connection is delta and the high voltage connection is wye. But these are for two different voltages at the same frequency.

What you have is a motor with different rated voltages for different frequencies, and both of the ratings you give have the same V/Hz ratio. This means that both ratings are for the same connection, probably wye.

The motor is probably also rated for 230V 50Hz delta.

Jon

 

[jim gage]

Thanks Jon but it only stats 400v 50hz
And 480 v 60 hz on the name plate. Where would the 230 v rating be from if not on the motor name plate?

 

[jim gage]

The six motor leads are brought into the control cabinet and landed on the Berges U,V,W output terminal in pairs and in the motor they are wired in delta without the use of the terminal jumpers in the motor.

 

[ActionDave]

I am unable to contact the motor manufacturer in Italy and all research I find tells me to connect the low voltage name plate rating in delta and the high volt name plate rating in wye but my customer says they are sure it arrived on site originally in delta and this has me cautious due to their run of failure of this motor.

That would be true if the motor were a typical 230/460V dual voltage motor, however on some motors the 460V is the low voltage rating. Here is a quote from Jraef from another thread with a similar topic that explains it well...

What happens is that (especially with EU suppliers like this), the motor is designed as 690/400V 50Hz, but since 400V 50Hz is the same V/Hz ratio as 480V 60Hz, it is useable at 480V 60Hz, but only in the Delta (Low Voltage) configuration and since 828V is not valid anywhere (the Wye votlage), they don't bother to put it on the nameplate and confuse people.

Weg does the same thing on their larger motors, because in a lot of places, 690V 50Hz is getting more common for things that have long motor leads, like in mining applications.

Sounds like a possibility for your motor. If you hook it up in wye and run it unloaded and the amps are abnormally low then that would confirm that the delta connection is correct for 480V.

Italian IEC stuff is the worst. Good luck.

 

[jim gage]

Thank you
I hope I here from someone at Saccardo motor because I would feel more comfortable hearing the proper connection from the the manufacturer.

I will not be holding my breath waiting for their reply from my past experience with Italian suppliers.
I guess it is the name plate rating of 400 v 50 hz and 480 v 60 hz that has me so hesitant to let them run it.
I have done amp checks and test ran it and found that the Berges inverter was set to operate at 0 to 100 hz in its parameters and if the speed pot was below 45 hz the motor would run at over amps.
I reset the parameters at 50 hz minimum and 100 hz max and found the current was 43 amps at 480 volts and around 10.4 amps at 100 hz. This was with the saw blade in no load condition. Under load passing through stone there was little to no difference in current at both speeds.??

 

[jim gage]

I forgot to mention the above test was connected in delta.

 

[ActionDave]

460V 60Hz is the same ratio as 400V 50Hz

 

[jim gage]

Another problem I noticed with this motor is that the Berges inverter has no overload parameters available and there is no OL protection in the cabinet. They have overhauled this saw when they first purchased it and they also disconnected the internal 2 wire p leads fom the motor.
My next question is should I install an OL assembly on the inverter output to the motor or would reconnecting the thermal motor device to the inverter control along with installing the motor over temp parameters be sufficient?

 

[winnie]

Thanks Jon but it only stats 400v 50hz
And 480 v 60 hz on the name plate. Where would the 230 v rating be from if not on the motor name plate?

My apologies, I should have just stopped when I said 'both ratings are for the same connection'.

Motors will have their ratings for their standard connection. That is the only thing that the manufacturer _explicitly states_. But there are always different ways that you can connect and use the motor if you are willing to go 'off label'.

If, hypothetically, this were a motor that was 400V 50Hz wye, it would also be a 480V 60Hz wye motor. And also 'off label' it would be a 230V 50Hz delta motor.

But quoted above is a way that this might be a 400V 50Hz delta motor, which is also a 480V 60Hz delta motor, with an 'off label' 828V 60Hz wye connection (note that going to _higher_ than rated voltage is problematic because of voltage limits)

In any case, for _any_ motor the wye connection will be higher voltage than the delta connection.

-Jon

 

[Jraef]

Saccardo makes specialty spindle motors for the quarry industry, as in marble quarries, not crushed rock quarries. I've run into their motors a couple of times, they are actually quite good.

If they told you that it needs to be connected in Star (Wye) for the higher voltage, you should believe them. Just because someone had been using it in Delta for years does not mean they were not wrong...

Here is a picture of an older Saccardo motor I have, the nameplate shows the connections. This one happened to be 550V, but it shows that the motor needed to be connected in Star. On the other one that I worked on, it was the same for 460V.

 

[Jraef]

Also...
A Berges inverter drive was a brand-label deal from a US based company called TB Woods. TB Woods no longer exists, they were bought up by a Finnish company called Vacon, who was then bought up by a Danish company called Danfoss. The old TB Woods drives were still supported for a while by Vacon, but since the Danfoss merger, they are long gone. IIRC, the TB Woods drives did have motor overload protection built-in but it was funky, requiring two program settings; one for the motor FLA and one for the trip time. But because it was like that, it was NOT UL listed as such, so you had to use an external OL relay. Prior to 2005 VFD mfrs could get away with that, but starting then, UL changed the rules on the listing of VFDs, requiring I²t motor thermal protection, just like an OL relay. You might want to consider upgrading to a more modern drive now.

 

[jim gage]

Thanks Jraef
This is helpful.
I am going to add bi-metal overload protection on the load side of the drive. I am also going to connect it in wye and run some amp and volt test Hz tests.
Should know more after that but a nice new Allen Bradley for this
Saw is going to be my first recommendation due to the amount of production this thing is loosing during downtime.
On the topic of the thermal leads, what is your opinion on putting it in series with the start stop circuit on the drive?
That would function for stop if over heated correct?
Thanks Again

 

[Jraef]

Yes, putting the OL aux contact in series with the Stop button will serve to shut it down on an overload.

Just so you know what happens when you connect a motor in Delta when it was supposed to be Wye.
The effective voltage across the windings will be (in this case) 173% higher than the motor is designed for. The motor will still spin at the desired speed because speed is based on frequency, not voltage, but you will have been over saturating the windings continuously. That over saturation becomes heat in the motor, but because of the way that drive is programmed, it likely would not respond to that correctly and allow it to continue running. That would ex[lain why you lost 3 motors running it this way.

UNLESS...

There is a "trick" used when running a motor at ABOVE its base speed using a VFD, wherein you WIRE the motor at the lower voltage and APPLY the higher voltage, BUT you program the VFD as if it is the LOWER voltage again. That way, when you get to the full rated frequency and you want to make it go faster with the VFD, you can continue to do so, because the VFD thinks it is the lower voltage, and the motor is happy, up unitl (in this case) 173% speed or roughly 100Hz. So it MIGHT be that someone originally intended for this saw to be run like that, but later on, someone didn't understand that and reprogrammed the drive for the higher voltage, which then started killing the motors.