240 Delta Motor - Siemens 1LA4

MAKsys

Member
Location
SE Michigan
Occupation
Controls Engineer
I am dealing with an old mixer - the motor has me a bit puzzled. I'm guessing this motor is a bit more than 25 years old. It is a Siemens 1LA4 223 V3 225M - I haven't been able to locate details in a catalog, but the nameplate lists the voltage as 240 delta, 160 amp, 52 kW. It is connected to a 240v Wye-Delta starter (six leads). I would like to run this from a VFD - and get off the 240v service (switch to 480v).

I'm guessing I can run this motor from a 480v VFD, and set the Volts at 240 - but am a bit concerned on proper sizing and is the drive going to be particularly noisy running at reduced voltage?

From reading other posts on here, there are a number of really smart people here - any advice would be appreciated.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
You would have to connect it in the Delta pattern in the motor connection box because that's what it wants. Without seeing tech data on the motor we don't know if it is set up for the higher voltage, but probably not if it is a 6 lead motor that was designed for Wye-Delta starting.

Yes, you can program a 480V VFD for limiting the motor voltage to 240V at 60Hz and that would make the motor run correctly. Just remember to buy a 480V VFD rated for the 240V motor current (160A), not the HP, so in effect you will be buying a 125HP 480V drive for a 240V 52kW (40HP?**) motor. That alone may be worth looking into leaving the 240V service in place.

There is another down side though; when you have a 480V drive, the DC bus voltage will be twice that of a 240V drive, so the individual pulses going to the motor will be twice as high as it would be on a 240V drive. Problems with motor insulation breakdown, often not an issue on 240V drives and motors, WILL be an issue for you here. If that motor was not built as "inverter duty", and at that age is probably wasn't, then it may not last long doing this. So in addition to the higher cost of the VFD, you have to factor in the cost of your future down time when the motor fails. You could extend its life by adding a dv/dt filter to the drive, or even a sine wave filter, but that's going to FURTHER increase the cost, compared to just leaving it at 240V for the drive and motor, or switching to 480V and buying a new 40HP** 460V motor and a smaller VFD. Something to consider.

** 52kW equates to about 40HP, which means the 160A current rating seems exceptionally high. Is it a high pole count (slow base speed) motor?
 

MAKsys

Member
Location
SE Michigan
Occupation
Controls Engineer
Thanks for the reply.

The mixer is going to be relocated and the customer needs wants to be able to vary motor speed - hence the VFD. I knew I'd need a larger drive, but didn't realize how much bigger! I'm wondering if it would be possible to re-wind the motor for 480v service - or just get a new motor (though, being a flange-mount, german motor, probably rare and/or pricey). Motor speed is 1770 rpm - 4 poles.
 

kwired

Electron manager
Location
NE Nebraska
Has math changed that much? I thought 52 kW would equate to about 69 HP. Have I lost my mind?
Seems right to me, so does about 160 amps for a ~69 HP motor.

A 40 HP @ 480 volts motor would draw 52 amps per NEC tables - maybe some mix up there?
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Thanks for the reply.

The mixer is going to be relocated and the customer needs wants to be able to vary motor speed - hence the VFD. I knew I'd need a larger drive, but didn't realize how much bigger! I'm wondering if it would be possible to re-wind the motor for 480v service - or just get a new motor (though, being a flange-mount, german motor, probably rare and/or pricey). Motor speed is 1770 rpm - 4 poles.
A motor repair show should be able to rewind the machine for 480V, and could also use inverter rated magnet wire. Burning out the old wire will likely reduce the ultimate efficiency of the core, but probably not by much.

When your 6 lead motor is in the 'wye' configuration, it is effectively a 416V machine operating at reduced voltage when connected to the 240V supply. So you could connect in the 'wye' configurate, with the VFD programmed for a motor rating of 416V and 60Hz. The VFD would need to be able to supply 92A, far better than using a 480V VFD to supply a 240V 160A motor.

However the caution about DC rail voltage and damage to the insulation system certainly applies.

-Jon
 

MAKsys

Member
Location
SE Michigan
Occupation
Controls Engineer
Thank you all for the replies. I put in a call to our local motor shop to see what it would take to re-wire the motor (ultimately, I think that is the way to go).
 

MTW

Senior Member
Location
SE Michigan
I would suggest that you get a constant torque drive and oversize it, if they are going to use it on heavy materials. I've had customers twist off 3" drive shafts by filling the mixer completely full, and then trying to start it. Even after they have been told not to put a full load in, while at rest. With a drive at least, you will have a quicker overload response. But some operators cannot be trained.

If you need a 2nd opinion on a rewind price, I have a shop in Redford, MI that I use.
 

kwired

Electron manager
Location
NE Nebraska
Being 25 years old, I would have the bearings replaced if the motor is out to be re-wound.
I would expect motor shop to replace bearings if they are rewinding motor. Doesn't cost much if you have motor disassembled already vs if bearing would fail in short time after it is put back into sevice.
 
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