130s Drive DickDV

Just finished installing a Allen Bradley 130s inverter to control the speed of a tank agitator, checked the motor name plate which said Delta-440v, Star(Wye)-760v. Inverter supply was 440v and output was 440v so went ahead and connected in D. Problem was the drive was reaching 150% full current at 25hz and so could never get upto speed. Then changed the motor to star and unsurprisingly the current was only about 5A peak dropping to 1.7A at speed. My question is why did we have to connect in star when the motor plate states star 760v, and if it is right to connect in star then why does the installation manual not state this? Perhaps DickDV could shed some light on this?

Alex.

Given the motor nameplate data you supplied, I would have hooked it up delta also. You didn't say what the nameplate full-load current is in delta and wye but, if the current exceeded the nameplate delta current at 25Hz, I would have concluded that the motor was overloaded. You didn't say whether the agitator had any load on it when the delta current went so high.

If the motor is unloaded and runs up to full speed in the wye connection, I would suspect that the shaft hp or kw will be much lower than nameplate and the agitator will not work under load as intended.

I'd like to know the motor kw or hp and the nameplate currents in delta and wye before I comment further.

Thanks for the speedy reply DickDV. I'll have to check up the FLA of the motor tomorrow, as I'm at home now. To answer yor other question, no the vessel was empty when this was happenning so the reduction gearbox was the only load. Watch this space for further namplate details.

Ok DickDV I have checked the motor details and the full load current in Wye is 4.54A, 660-690v, and Delta 7.62A, 415v, 4KW. When I ran the motor the current was reaching 12Amps with only the gearbox as the load, the vessel was empty. Do you think the installation was badly designed, posibly useing the wrong type of gearbox? Are there any long term problems running the motor in wye with only 415v supply? I have checked 2 other vessels on the plant that have the same set-up, but these were installed before I joined the company and have been running without problems so far.

Any further information would be greatly appreciated.

Alex

I would say that there is nothing wrong with running this motor in wye with 440V at 50Hz but you will not get the full output power of the motor. If the output is enough to do the work in the agitator, then all will be well.

You could probably increase the available torque from the motor at lower speeds by customizing the V/Hz curve in the drive. If the wye nameplate info states 660VAC at 50Hz and all you have available is 440V, then you could set the V/Hz curve to reach 440V at 33Hz. That would duplicate a curve that reached 660V at 50Hz up to 33Hz and should give you design torque at least from 33Hz down. Above 33Hz, the torque will fall as a function of the inverse of the overspeed from 33Hz but, at no time will it be less than if you had set the curve for 440V at 50Hz.

There definitely seems to be something wrong about the current draw of the motor in the delta configuration. I can't tell what it is but it certainly should not be 12 amps at no load. Oh well, if it does the job you want in wye, just use it that way. Good luck!