Run 400v motor @ 480v?

[milemaker13]

Installing a dust collector with 30 hp motor. Tag says 200/400 volts. Our facility has 480v(492v generally).
What is my best option here? Transformer? New/ rewound motor? Run as is?

The starter and such that came with this second hand dust collector seem to suggest it was run at 480 in the past. What will happen (how quickly) if we decide to run it as is at 480 volts?

 

[jumper]

Similar thread you can read while you wait for responses.

http://forums.mikeholt.com/showthread.php?t=116389

 

[growler]

Installing a dust collector with 30 hp motor. Tag says 200/400 volts. Our facility has 480v(492v generally).
What is my best option here? Transformer? New/ rewound motor? Run as is?

The starter and such that came with this second hand dust collector seem to suggest it was run at 480 in the past. What will happen (how quickly) if we decide to run it as is at 480 volts?

If it's an old motor I would probably run it as long as it will last at 480V and then have it rewound (480V) or purchase a 480V motor.

If you know who owned it before you could call and ask if they ran it at 480V.

 

[milemaker13]

Thank you. It was similar except our motor is 400v/ 60 Hz . I suspect the original owners ran a shop full of European machinery and ordered the dust collector at their shop voltage of 400.
That thread talked about volt/ Hz ratio, and by jumping up both volts and Hz that ratio stayed the same. My ratio will change as the Hz will not change.
It basically said it would be ok, if you can handle a bit more rpm. But more rpm on a fan(dust collector) would increase hp required, which in turn could over load the motor.
So I'm still asking the same question: can I run a 400v/60hz motor at 492v/60hz with out immediate damage?

 

[LarrywdH]

Are you sure it's rated at 60hz?
Most 400v motors are for Europe and are 50hz.

 

[Jraef]

I'll reiterate what I said in the other thread for emphasis.

Electrically, the motor will work fine. The ratio of Voltage and Frequency is exactly the same (400/50 = 8.0, 480/60 = 8.0), so the motor will work at 480V 60Hz and provide it's full rated torque at nameplate FLA without issue. But the problem is with the load. Most likely your dust collection blower is a centrifugal type. So the bigger issue is the fact that as a 400V motor, it was designed to run at 50Hz, not 60Hz. That motor was selected based on the mechanical shaft power it was capable of delivering at 50Hz, in this case 30HP (or more likely, 22kW). When that fan spins at 60Hz, the HP the FAN REQUIRES will go up by the cube of the speed change, so 173% of what the fan required at 50Hz. We don't know what the fan actually REQUIRED, only that the motor was picked to be equal to or greater than that value. But let's say it was a conservative engineer who allowed for a 20% "fudge factor". That would put the fan requirement at 24HP at 50Hz. At 60Hz then, that same fan will require almost 42HP, but the motor will only deliver 36HP. It will overload.

So you have two choices:
1) If there is a belt drive you can change the sheave ratio so that the fan itself turns at the same speed it would have at 50Hz, i.e. 20% slower than the 60Hz speed.
Or
2) If there are dampers, you can choke off the air flow of the fan and watch the motor current until you make sure the motor current is at or below FLA.

PS: Crossed in the ether: I now see that you have a unicorn motor rated 400V 60Hz. Assuming that is correct, then somehow increasing the voltage to 492V would be the opposite of what you need to do, you would need to LOWER your voltage to 400V 60Hz, just as the motor says it requires. I now think your better option will be to add a VFD to this motor and give it exactly what it is designed for. You can feed a VFD with 480V and program it to output 400V at 60Hz.

But seriously, triple check the actual motor nameplate. 400V 60Hz is a real oddball combination.

 

[winnie]

Just to be clear:

If this is _actually_ a 400V 60Hz motor, then running it at 492V is a significant increase in V/Hz ratio which can cause real problems if it pushes the motor into saturation.

We as a group believe that you actually have a 400V 50Hz motor because this is a very common value. In which case Jraef's comments apply.

You have said several times that you have a 400V 60Hz motor, but we would ask you to carefully confirm this before we make any further comments.

-Jon

 

[milemaker13]

Yes, it is 400v/ 60Hz fo sho.

 

[Besoeker]

/

Thank you. It was similar except our motor is 400v/ 60 Hz . I suspect the original owners ran a shop full of European machinery and ordered the dust collector at their shop voltage of 400.
That thread talked about volt/ Hz ratio, and by jumping up both volts and Hz that ratio stayed the same. My ratio will change as the Hz will not change.
It basically said it would be ok, if you can handle a bit more rpm. But more rpm on a fan(dust collector) would increase hp required, which in turn could over load the motor.
So I'm still asking the same question: can I run a 400v/60hz motor at 492v/60hz with out immediate damage?

I don't know.
A couple of things to think about.
How critical to production is that piece of plant?
How would down time costs compare with a new motor?

 

[Besoeker]

1) If there is a belt drive you can change the sheave ratio so that the fan itself turns at the same speed it would have at 50Hz,

If it was rated at 50Hz which we are told it isn.t.

 

[milemaker13]

Ok, we're looking at a new motor to run 480.

But, I know this place... the new motor is a $2k oops. I think a VFD would cost at least that much of not more. What is worst case when they say to just run it as is? Will all of the smoke come out?

Ridiculous, I know... Welcome to my world. :happysad:

 

[winnie]

Again, 400V 60Hz is a strange beastie. Is there any chance that it was a rewind job rather than 400V 60Hz from the factory?

Some background: an induction motor (I am guessing this is what you have) draws both 'magnetizing current' and 'running current'. Of course the actual current drawn is a composite of these two, so what you see in th composite is a single current with a power factor angle. The greater the magnetizing current or the lower the running current, then the lower the power factor.

Increasing the motor V/Hz will tend to _increase_ the magnetizing current but _decrease_ the running current.

What you are concerned bout is the increase in magnetizing current because if you increase it too much you will let the smoke out of your motor. The issue here is 'saturation'. The motor steel carries magnetic flux and increases the inductance of the motor windings, which reduces the magnetizing current. Once the steel is asked to carry too much flux the inductance of the motor windings drops precipitously and the magnetizing current jumps.

So the question is: how close to saturation is the motor as designed at 400V. If the motor were designed conservatively, then it would probably tolerate the 480V. If it is close to the edge you will let the magic smoke out after a few minutes.

IMHO with a 20% overvoltage you will not see an instantaneous failure, but rather an overheating failure after short period of time. So it might be reasonable to _test_ unloaded operation at 480V and measure what the current is. If the magnetizing current comes low enough then just use the machine at 480V. (I can't give you a precise value of 'low enough', but anything less than rated FLA of the motor would make further exploration reasonable).

If you need 400V, then you have options:

1) A 'buck-boost' transformer taking 492V down to about 410V will cost about $800 (see page 9 (labeled 87) of https://www.hammondpowersolutions.com/files/HPS_Catalog_BuckBoost_Section2.pdf ) figure the part number and look up the price.

2) A VFD would cost about $2K but would offer potential energy saving benefits. First a VFD can take a 480V input and give you a 400V at 60Hz output. Second you can use it to vary the frequency and thus speed of the motor. A dust collector is moving air, and during times of low load you may be throttling the air flow. You save significant energy if you can open a throttle and then get the reduced air flow with reduced motor speed. If you can drop power consumption by 20% for 50% of time (assuming continuous run) then you pay for the inverter in a single year from the energy savings.

3) A motor repair shop can rewind the motor for 480V operation

4) Depending on how the motor is wired, you might be able to change it over to 200V operation in the terminal box, and then operate from an available 208V supply (if you have such in your facility).

5) You can replace the motor with one rated for 480V 60Hz.

-Jon

 

[ptonsparky]

Options:
1. New motor $2100.
2. VFD $1600 plus parts
3. Connect and run what you have. Wait for smoke to be released. Have #1 on hand.

 

[ptonsparky]

I’m not sure if our local rewind shop would go to the effort of rewinding a 30 hp motor from 400 to 480. I would tend to think there would be very little if any savings.

Where is our motor guy(s) on this?

 

[mike_kilroy]

Thank you. It was similar except our motor is 400v/ 60 Hz . I suspect the original owners ran a shop full of European machinery and ordered the dust collector at their shop voltage of 400.
That thread talked about volt/ Hz ratio, and by jumping up both volts and Hz that ratio stayed the same. My ratio will change as the Hz will not change.
It basically said it would be ok, if you can handle a bit more rpm. But more rpm on a fan(dust collector) would increase hp required, which in turn could over load the motor.
So I'm still asking the same question: can I run a 400v/60hz motor at 492v/60hz with out immediate damage?

No. Simple and concise answer.

Sent from my SM-G900V using Tapatalk

 

[mike_kilroy]

Again, 400V 60Hz is a strange beastie. Is there any chance that it was a rewind job rather than 400V 60Hz from the factory?

Some background: an induction motor (I am guessing this is what you have) draws both 'magnetizing current' and 'running current'. Of course the actual current drawn is a composite of these two, so what you see in th composite is a single current with a power factor angle. The greater the magnetizing current or the lower the running current, then the lower the power factor.

Increasing the motor V/Hz will tend to _increase_ the magnetizing current but _decrease_ the running current.

What you are concerned bout is the increase in magnetizing current because if you increase it too much you will let the smoke out of your motor. The issue here is 'saturation'. The motor steel carries magnetic flux and increases the inductance of the motor windings, which reduces the magnetizing current. Once the steel is asked to carry too much flux the inductance of the motor windings drops precipitously and the magnetizing current jumps.

So the question is: how close to saturation is the motor as designed at 400V. If the motor were designed conservatively, then it would probably tolerate the 480V. If it is close to the edge you will let the magic smoke out after a few minutes.

IMHO with a 20% overvoltage you will not see an instantaneous failure, but rather an overheating failure after short period of time. So it might be reasonable to _test_ unloaded operation at 480V and measure what the current is. If the magnetizing current comes low enough then just use the machine at 480V. (I can't give you a precise value of 'low enough', but anything less than rated FLA of the motor would make further exploration reasonable).

If you need 400V, then you have options:

1) A 'buck-boost' transformer taking 492V down to about 410V will cost about $800 (see page 9 (labeled 87) of https://www.hammondpowersolutions.com/files/HPS_Catalog_BuckBoost_Section2.pdf ) figure the part number and look up the price.

2) A VFD would cost about $2K but would offer potential energy saving benefits. First a VFD can take a 480V input and give you a 400V at 60Hz output. Second you can use it to vary the frequency and thus speed of the motor. A dust collector is moving air, and during times of low load you may be throttling the air flow. You save significant energy if you can open a throttle and then get the reduced air flow with reduced motor speed. If you can drop power consumption by 20% for 50% of time (assuming continuous run) then you pay for the inverter in a single year from the energy savings.

3) A motor repair shop can rewind the motor for 480V operation

4) Depending on how the motor is wired, you might be able to change it over to 200V operation in the terminal box, and then operate from an available 208V supply (if you have such in your facility).

5) You can replace the motor with one rated for 480V 60Hz.

-Jon

Perfect! Complete answer.

Sent from my SM-G900V using Tapatalk

 

[JFletcher]

Installing a dust collector with 30 hp motor. Tag says 200/400 volts. Our facility has 480v(492v generally).
What is my best option here? Transformer? New/ rewound motor? Run as is?

The starter and such that came with this second hand dust collector seem to suggest it was run at 480 in the past. What will happen (how quickly) if we decide to run it as is at 480 volts?

One not mentioned possibility is adjusting the xfmr taps to lower your incoming voltage; you may want to look into that anyway if you're running 492V under normal operations.