Can a motor rated for 460VAC 3-Phase 50Hz be used with 400VAC 3-Phase 60Hz Power 8

[colombo7]

Motor Data:
7.5 kW 230/460V 50 Hz.(Delta or Y Configuration)

Does the above mean if Plant supply 460VAC (more than likely 480VAC) is connected to the motor using a DELTA connection that it is running at 230VAC and if connected in a "Y" configuration motor is being supplied 400VAC?

Can this motor be used with incoming power (Plant power) set at 400VAC at 60 HZ using a VFD?

Thanks.

 

[jraef]

Are you sure you have that right?

400V 60Hz is only used in a couple of small countries, like Montserrat, Trinidad and Tobago (although it was used here in the US back in the 70s for IBM mainframes back when those were a thing). 460V 50hz is not used anywhere that I'm aware of. If your motor says that, it would not be a Delta/Wye connection for 230/460V because the voltage difference for D/Y is 1.732:1, not 2:1. You have miscommunicated something or are being given incorrect information somewhere.




" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[colombo7]

Jraef,

You are correct. My mistake. It was 7.5 kW / 230/400VAC (and not 460VAC) / Delta/Y at 50Hz.

If I were to interpret the above...this tells me that I can supply the motor with either 3-Phase 230VAC or 400VAC at 50 Hz. Is that correct?

Which wiring configuration (Delta or Y) to use? What dictates which configuration to use?

If line voltage is 3 Phase 400VAC at 60Hz (not 50Hz), Can I wire up a VFD to 400VAC input but run the motor at 230VAC at 50Hz Max? (i.e. limit VFD Power output and Freq Output to the motor?)

Thanks.

 

[edison123]

Regardless of frequency, a dual voltage motor is connected in delta for lower voltage and in Wye for higher voltage.

Muthu

http://www.edison.co.in

 

[colombo7]

edison123,

Thanks, that clarifies the delta/Y connections.

Still looking for answer to the following.

230/460VAC at 50Hz (Motor rating)

What would the equivalent low voltage (for a DELTA Connection) be at 400VAC 60Hz line voltage?

Is it 200VAC. How do I figure that? ideally, I want the motor to behave exactly like it would at 230VAC (with a line input of 480VAC)in DELTA configuration at 50HZ, but with 400VAC and 60Hz using a VFD.

Thanks.

 

[edison123]

Again regardless of frequency, a 400 V wye connection becomes a 230 V delta connection.


Muthu

http://www.edison.co.in

 

[colombo7]

Edison123,

Pardon my ignorance. In the earlier post you said Delta is used for lower voltage and later you commented that "WYE" is used for lower voltage, both regardless of frequency. I get the frequency part.

In essence, you are also saying that 460VAC's lower voltage is 230VAC and 400VAC's lower voltage is ALSO 230VAC?. Unless I misunderstood what you were trying to convey.

There is so much conflicting information. I am trying to find the correct answer. Perhaps I might not be asking the question properly.

 

[waross]

Please go back and read the name plate again.
230/460 is a common 60 Hz, 9 lead series-parallel connection. Ratio 1:2
230/400 is a common 50 Hz, 6 lead wye-delta connection. Ratio 1:1.73

230/460 50 Hz does not compute.
230/460 wye-delta does not compute.
Now if this is actually a 400 Volt, 50 Hz wye connected motor it may be operated on 400V x (60Hz/50Hz) = 480 Volts, 60 Hz.
The motor will run 20% faster but will have the same torque as at 400 V, 50 Hz.
You may configure the VFD for a motor of 480 Volts at 60 Hz, or for a motor of 400 Volts at 50 Hz.
Then dial the speed that you need.
But first, please, reread the nameplate.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Edison123 didn't post conflicting information.

For wye vs delta connections, the voltage ratio is always wye = 1.73 x delta.
For wye vs delta connections, delta is always the lower voltage and wye is always the higher voltage.

You can always set a VFD to produce an output voltage up to the line voltage being supplied. 400VAC supplied means the VFD can produce up to 400VAC on the output. 480VAC supplied means the VFD can produce up to 480VAC on the output. This is regardless of frequency. I've setup a VFD connected to 480VAC to produce 460VAC at 6.7Hz before.

 

[waross]

I apologize Columbo7. I missed your correction to 230/400 Volts.
However in my defense I note that after the correction you again posted the wrong (460V) voltage value.
Remember, as the voltage drops by a ratio of 1.73:1 the current increases by a ratio of 1:1.73.
Further to Lionel's post, you could set the motor up as delta at 230 Volts but the VFD will be more expensive than if you use a wye connection at 400 Volts.
At 400 Volts and 50 Hertz, the Volts per Hertz ratio is 8:1 This is important and should be maintained.
A 400 Volt, 50 Hz motor may be used on 60 Hz at any voltage up to 60Hz x 8V/Hz = 480 Volts, subject to load constraints.
If the V/Hz ratio is too high, the motor may go into saturation and quickly overheat.
If the V/Hz ratio is too low, the maximum safe torque will be less than optimum.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[colombo7]

edison123,

My apologies about conflicting information. I misread your second post. You were correct in both.

Waross,

Unfortunately I do not have the nameplate or picture of it at the moment and won't be getting it from the customer for another month or so. You said...."Now if this is actually a 400 Volt, 50 Hz wye connected motor it may be operated on 400V x (60Hz/50Hz) = 480 Volts, 60 Hz."

It is. From the information that was given to me, it states;

7.5Kw
230/400VAC
D/Y
50Hz
Freq. Converter operation (S9) in DELTA connection up to 100Hz
7.5kW: 230VAC 3000 RPM at 50Hz
15kW: 460VAC 6000 RPM at 100Hz (How is this possible? In Delta configuration, shouldn't this be 230VAC? Or is it saying it can be supplied with 460VAC but motor will only see 230VAC?)

Going back to your statement;

"Now if this is actually a 400 Volt, 50 Hz wye connected motor it may be operated on 400V x (60Hz/50Hz) = 480 Volts, 60 Hz."

Does this mean I can operate this motor with a line voltage of 400VAC 60Hz (at VFD Input), but the motor will be connected in a Delta configuration where it will only see 230VAC at it's connections?

Thanks again for everyone's help.

 

[LionelHutz]

Motors follow really nice ratios when you use a VFD.

The motor always wants a constant V/Hz ratio to maintain a constant rated torque, so get the V/Hz first.
230/50 = 4.6 V/Hz

Now,
At 25 Hz, you'd want to apply 25 Hz x 4.6 V/Hz = 115 V
At 75 Hz, you'd want to apply 75 Hz x 4.6 V/Hz = 345 V
At 100 Hz, you'd want to apply 100 Hz x 4.6 V/Hz = 460 V

Since the rated torque remains the same, ratio the frequencies to get the rpm and HP at the different frequencies, so get those ratios.
3000/50 = 60 rpm/Hz
and
7.5/50 = 0.15 HP/Hz

This means:
At 25 Hz,
rpm = 25 Hz x 60 rpm/Hz = 1500 rpm
HP = 25Hz x 0.15 HP/Hz = 3.75 HP

At 75 Hz,
rpm = 75 Hz x 60 rpm/Hz = 4500 rpm
HP = 75Hz x 0.15 HP/Hz = 11.25 HP

At 100 Hz,
rpm = 100 Hz x 60 rpm/Hz = 6000 rpm
HP = 100Hz x 0.15 HP/Hz = 15 HP

Keep in mind that the above rpm's are the synchronous speed of the motor. It will always slip a bit. It may run at 50 rpm below the synchronous speed when at full load.

The short form reason why this works - To get a constant torque requires a constant magnetic flux. The flux is produced by current. Since the inductance of the coils varies directly with frequency you need more voltage to keep the current constant as you increase frequency.

 

[colombo7]

LionelHutz,

Thank you so much for that detailed explanation. I am still a bit confused about the Delta & Wye configuration as it applies to incoming line voltage. Taking the following motor spec in to consideration;

230/400VAC
D/Y
50Hz

Does this mean I need 230VAC line power if I want to run this motor using the DELTA connection and 400VAC incoming line power to connect it using the Wye configuration? I was under the assumption if I had incoming power at 400VAC I can still use that to run the above motor configured in a DELTA configuration and the motor would see 230VAC as its supply voltage.

 

[edison123]

"I was under the assumption if I had incoming power at 400VAC I can still use that to run the above motor configured in a DELTA configuration and the motor would see 230VAC as its supply voltage."

You are wrong. As the nameplate and others have clearly stated here, if your source is 400 V, you connect the winding leads in wye and if your source is 230 V, you connect the leads in delta. It's not that complicated.


Muthu

http://www.edison.co.in

 

[waross]

Well said, Lionel.
Consider two separate motors.
#1> 230 Volts @ 50Hz, Volts per Hz ratio = 230/50 = 4.6
#2> 400 Volts @ 50 Hz, Volts per Hz ratio = 400/50 = 8
Whichever motor you consider depends on whether you use a delta or wye connection.

With a delta connection and 100 Hz supplied by the VFD the motor is safe to apply 100Hz x V/Hz ratio 4.6 = 460 Volts.
The motor will still accept rated amps and will deliver rated torque, but at 100 Hz the motor will run at 6000 RPM.
The same torque and double the speed equals twice the HP.

With a wye connection you may apply 480 Volts @ 60 Hz directly to the motor.

With a VFD, you may wire the motor in delta and supply the VFD with 460 Volts. The VFD (properly configured) will supply the motor with 230 Volts at 50 Hz. With an input voltage of 460 Volts or 480 Volts, the VFD is also capable of supplying 460 volts at 100 Hz.

What are you going to use the motor for?
What speed range do you need?
What HP do you really need?
Can you work with a fixed speed of 3600 RPM?
If you can use 3600 RPM 480 Volts then you may not need a VFD.

("I was under the assumption if I had incoming power at 400VAC I can still use that to run the above motor configured in a DELTA configuration and the motor would see 230VAC as its supply voltage.") I understand that this is with a VFD supplied with 400 Volts, and outputting 230 Volts to the motor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[colombo7]

edison123,

With all due respect, I know I wasn't correct, hence the request for additional clarification.

After all, you replied..."regardless of frequency, a 400 V wye connection becomes a 230 V delta connection."

What does this even mean? How does a 400V Wye becomes a 230V Delta?

Perhaps may be if you had worded the above to say...if line voltage is 400VAC, then a Wye connection must be used and for a line voltage of 230VAC, a Delta connection must be used. Then I wouldn't have had to ask what might seem like a dumb question to you.

Cheers.

 

[edison123]

colombo

With all due respect, you got more than what you paid for here. Your mistaken understanding of posts is your problem.

Muthu

http://www.edison.co.in

 

[colombo7]

Waross,

Thanks for the explanation. You are getting close to what I am trying to learn and understand.

Consider two separate motors.
#1> 230 Volts @ 50Hz, Volts per Hz ratio = 230/50 = 4.6
#2> 400 Volts @ 50 Hz, Volts per Hz ratio = 400/50 = 8
Whichever motor you consider depends on whether you use a delta or wye connection.

With a delta connection and 100 Hz supplied by the VFD the motor is safe to apply 100Hz x V/Hz ratio 4.6 = 460 Volts.
The motor will still accept rated amps and will deliver rated torque, but at 100 Hz the motor will run at 6000 RPM.
The same torque and double the speed equals twice the HP.

So this implies that I must supply the motor #1 configured in a DELTA configuration with 460VAC at 100 Hz, and as long
I maintain the V/f ratio of 4.6 and it will have the same torque as if it was running at 3000RPM at 230VAC/50Hz?

So in theory, if this was a pump pumping 100gallons a minute at 3000RPM, it would now be pumping 200gallons a minute provided the impeller can withstand the increased RPM. Is that assumption correct or am I way off in my thinking?

 

[waross]

Well yes but:

So in theory, if this was a pump pumping 100gallons a minute at 3000RPM, it would now be pumping 200gallons a minute provided the impeller can withstand the increased RPM. Is that assumption correct or am I way off in my thinking?

The load on the motor would now be 4 times what it was when it was pumping 100 GPM.
I would estimate the life of the motor to be under 5 minutes if the over-load protection didn't take it off line.
I am sure that Keith will agree that some would give it much less than 5 minutes. grin.
Really columbo7; If you want to know about motors, get a good book. An easy to understand short course is the Cowern Papers by Edward Cowern PE.
Cowern Papers
Also, as an industrial engineer, look at some manufacturers pump charts.
Many times you will see the same pump specs running at 1800 RPM and running at 3600 RPM.
You will quickly see a four to one ratio in motor size. When you compare a pump at 1800 to the same pump running at 3600 RPM the motor on the 3600 RPM pump will be four times the HP.

If you have a specific problem or application, give us the details up front instead of leading us around with guessing games.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[colombo7]

Waross,

Thanks for the reply.

If you have a specific problem or application, give us the details up front instead of leading us around with guessing games.

I do not have a specific problem per say (at least not yet), nor am I trying to lead anyone around with guessing games. Just trying to understand the operation of a specific system. I am not an electrical engineer so my questions may not be in line with what is common knowledge for you and your peers. All I am trying to do is trying to understand System X, that was running at a facility having 400VAC 50Hz power, to get it to run the same way at a Facility having 400VAC 60Hz.

For the time being, all the information that I have about this is a motor that is used in a Water pumping application. This is all the information that I have about the said motor and how it was controlled.

7.5Kw 230/400VAC D/Y 50Hz
Freq. Converter operation (S9) in DELTA connection up to 100Hz
7.5kW: 230VAC 3000 RPM at 50Hz
15kW: 460VAC 6000 RPM at 100Hz

So in one of your replies you stated.....

With a delta connection and 100 Hz supplied by the VFD the motor is safe to apply 100Hz x V/Hz ratio 4.6 = 460 Volts.
The motor will still accept rated amps and will deliver rated torque, but at 100 Hz the motor will run at 6000 RPM.
The same torque and double the speed equals twice the HP.

In your last reply you stated....

The load on the motor would now be 4 times what it was when it was pumping 100 GPM.
I would estimate the life of the motor to be under 5 minutes if the over-load protection didn't take it off line.
I am sure that Keith will agree that some would give it much less than 5 minutes. grin.

Please know that I am not trying to nit-pick nor find fault but rather trying to understand this. I am confused as to why would an OEM even bring up S9 mode operation for this motor at 460VAC 100Hz, if the said motor would die off after 5 minutes of operation?

I am simply trying to understand what the specified characteristics for this motor means in layman's terms. Thanks again for all your help and pointers. I am getting some of it, but still failing to see the Forrest from the trees.

Best regards.