# VFD question



## browningwgm

Hello,

A little background on myself. I'm an active duty HVAC tech serving in USAF. I'm currently deployed to a location in Southwest Asia. I have been asked to look at an issue with a water distribution system. They have 8 45KW (60HP) pumps that are delta wound running 415 VAC 3 ph 50hz. There's 6 power leads going to the motor.

Motor data plate states
400 Delta 50hz
690 Wye 50hz

460 delta 60hz

What I want to know is, can this motor be ran off a VFD? The current setup uses 3 contactors. At startup, the start and shorting contactors pull in. After a couple seconds, the shorting contactor drops out and at the same time the run contactor will pull in. This seems to be a pretty standard start sequence that I've seen on some larger chiller units before.

My goal is to run these pumps off a VFD to avoid constant start/stops that's occuring and wearing out our equipment.

If you need more info, please let me know and I can get it. Any help would be appreciated. Thanks.


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## 5volts

browningwgm said:


> Hello,
> 
> A little background on myself. I'm an active duty HVAC tech serving in USAF. I'm currently deployed to a location in Southwest Asia. I have been asked to look at an issue with a water distribution system. They have 8 45KW (60HP) pumps that are delta wound running 415 VAC 3 ph 50hz. There's 6 power leads going to the motor.
> 
> Motor data plate states
> 400 Delta 50hz
> 690 Wye 50hz
> 
> 460 delta 60hz
> 
> What I want to know is, can this motor be ran off a VFD? The current setup uses 3 contactors. At startup, the start and shorting contactors pull in. After a couple seconds, the shorting contactor drops out and at the same time the run contactor will pull in. This seems to be a pretty standard start sequence that I've seen on some larger chiller units before.
> 
> My goal is to run these pumps off a VFD to avoid constant start/stops that's occuring and wearing out our equipment.
> 
> If you need more info, please let me know and I can get it. Any help would be appreciated. Thanks.


 
In my opinion Wye-delta starting is a old school way to reduce voltage starting and reducing heat in the motor. The Variable Frequency Drive is much more capable of starting the motor without inducing heat in the motor windings. Just wire the motor delta (run). 

By the way welcome to the forum!


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## micromind

These motors can indeed be run with a VFD. 

I don't recall the IEC lead numbers, but if they're numbered to NEMA standards, T1 of the VFD will connect to 1&6, T2 go to 2&4, and T3 go to 3&5. If the motor turns backward, rotation must be changed at the motor, or the load side of the VFD. Changing two leads of the line side will have no effect on the output. 

Rob


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## browningwgm

Thanks all for the info. The motor has 6 lugs, 3 wires coming from the Main contactor and 3 wires coming from the Delta contactor. I'll try and get some more info but it's a German motor and I'm not familiar with their terminology. I'll try and get photos.

I do have some photos of the control schematic.

When you say I need to wire the motor for Delta run, can you explain this further. There's no wiring diagram on the motor that I can find. Once I get photos of the actual motor wiring configuration you may be able to better help me out.


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## John Valdes

Go for it. Hows your power quality? I highly recommend using a line reactor with the VFD. I would think your power quality may not be optimum. (Asia)


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## MDShunk

How old is this installation? Seems like the only stuff I've seen that still has a star-delta starter is quite old.


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## 5volts

browningwgm said:


> When you say I need to wire the motor for Delta run, can you explain this further. There's no wiring diagram on the motor that I can find. Once I get photos of the actual motor wiring configuration you may be able to better help me out.


The load side of the VFD would be wired as suggested in post #3. But double check the motor wiring from the manufacturer.


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## micromind

According to the drawing, the motor is labeled per IEC spec's. U1, U2, V1, V2, W1, W2.

The connections would be; T1 of the VFD would go to U1 and W2. T2 goes to V1 and U2. T3 goes to W1 and V2. 

Rob


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## browningwgm

MDShunk said:


> How old is this installation? Seems like the only stuff I've seen that still has a star-delta starter is quite old.


The equipment's only a few years old and would never have been allowed to be installed in its current state if this were stateside. I'm trying to make a bad situation better.


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## browningwgm

John Valdes said:


> Go for it. Hows your power quality? I highly recommend using a line reactor with the VFD. I would think your power quality may not be optimum. (Asia)


From what I've seen, power quality isn't all that bad.


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## browningwgm

micromind said:


> According to the drawing, the motor is labeled per IEC spec's. U1, U2, V1, V2, W1, W2.
> 
> The connections would be; T1 of the VFD would go to U1 and W2. T2 goes to V1 and U2. T3 goes to W1 and V2.
> 
> Rob


That's what I was thinking but wanted to get some second opinions. Thanks for yours and everyone elses assistance.


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## varmit

*Wye-Delta conversion*

Rob,
A VFD is an easy conversion to this set-up. However, post #3 is incorrect about the motor connection: The motor must be connected in the Delta "run" mode. The drive leads would connect to motor leads U1, V1, & W1.
Motor leads U2, V2 and W2 would connect together - as if the jumper contactor was pulled in at all times.

You could simplify the control logic quite a bit as the drive would only need a start and stop input if wired for 3 wire control. The speed reference, to the drive, I am assuming, would be based on system pressure. 

One thing to look at, that can cause a problem, would be if the pumps pump up to a considerable elevation gain or have a potential to have back pressure. If you encounter reverse flow through a VFD driven pump you can get a "buss overvoltage fault" as the motor can become a generator and feed excess energy back to the drive. The fix, if this problem shows up, is to install a dynamic braking resistor connected to the "brake" terminals at the drive.

A line reactor is always a good idea on the line side of a VFD as the drive high speed switching can cause frequency increases to the distribution system back to the nearest transformer in the circuit.

While Wye-Delta starters are rare in the US, except for 100 HP and larger, they are still quite common on European (IEC) equipment.

I hope that this helps.
Harry


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## browningwgm

varmit said:


> Rob,
> The drive leads would connect to motor leads U1, V1, & W1.
> Motor leads U2, V2 and W2 would connect together - as if the jumper contactor was pulled in at all times.


I'm confused now. I'm going to try and get photos of the actual wiring on the motor today.



varmit said:


> You could simplify the control logic quite a bit as the drive would only need a start and stop input if wired for 3 wire control. The speed reference, to the drive, I am assuming, would be based on system pressure.


Pump speed would be controlled by a pressure transducer. I'll install a DDC controller, tie in the transducer, and output a 0 to 10 VDC signal to the VFD based on system pressure.



varmit said:


> One thing to look at, that can cause a problem, would be if the pumps pump up to a considerable elevation gain or have a potential to have back pressure. If you encounter reverse flow through a VFD driven pump you can get a "buss overvoltage fault" as the motor can become a generator and feed excess energy back to the drive. The fix, if this problem shows up, is to install a dynamic braking resistor connected to the "brake" terminals at the drive.


There isn't a large elevation gain. Two story bldgs are the tallest being pumped to. Each pump has a check valve installed to prevent backflow


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## browningwgm

Here's some photos of the actual motor wiring and diagram.










According to this diagram and since I'm running low voltage 400V 3ph 50hz, I would use the delta option with U1 to W2, V1 to U2 and W1 to V2, just like micromind states. The wye option would be used for 600 VAC 3 ph 50hz or 460 VAC 3 ph 60hz. Am I reading this correctly.

Here's the actual motor wiring.


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## John Valdes

Wye for high voltage and delta for low voltage on a *six lead motor* dual voltage motor.

Delta is only used for run on a single voltage 6 lead motor.


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## PLCMentor.com

I think a word of caution needs to be added about the motor. I think we can safely assume that this motor is not an inverter duty motor. A VFD generates a signal that can be very hard on the motor windings. An inverter duty motor is designed to be able to compensate for that. You may want to contact the manufacturer and try to determine what effect adding a VFD will have on the motor life. 

Russell


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## micromind

Varmit; Post #3 describes a delta connection. Your post describes a wye connection. Please study these connections very carefully before telling someone they're wrong. 

Look very carefully at the motor connection diagram.

The motor must be connected delta, not wye. 

If it is connected wye, it'll turn a centrifugal pump, but not all that fast. It'll develop about 1/3 of its nameplate HP. 

Rob


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## browningwgm

PLCMentor.com said:


> I think a word of caution needs to be added about the motor. I think we can safely assume that this motor is not an inverter duty motor. A VFD generates a signal that can be very hard on the motor windings. An inverter duty motor is designed to be able to compensate for that. You may want to contact the manufacturer and try to determine what effect adding a VFD will have on the motor life.
> 
> Russell


Here's the data plate. I know, I was upset also. I asked someone to get me the info off the motor and this is what they brought me. They now know better. Is there anything on there that lets you know if it's inverter duty rated? Thanks.


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## PLCMentor.com

No spreken... In fact I dont even know how to spell that. I dont see anything that indicates it is inverter duty. In fact I would assume that it is not. I would suggest contacting the manufacturer and describing how you intend to use it. They will probably take the safe out and say it's not designed for that, but you might get some good info. You also might talk with the drives rep/manufacturer and see if there are any reasonably priced filters that you can intstal at the motor. 

Ha! I just got what you said! You mean someone just popped the plate off the motor! I'd be careful about asking for information on the cable type.

Russell


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## lukejenson

Even tho it says KSB on the nameplate, it looks like a lenze nameplate to me.

does the motor looks anything like the ones on the following page?

http://www.ctiautomation.net/Lenze-AC-Motors.htm


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## yindavies

*VFD help*

Go for an ABB acs800 75KW. They dont do a 55kw anymore. They pack the 75KW into the 55 frame size. I have just been quoted an unbelievable price for one. 

At 75kw the line reactor comes with it.

They will also get massive energy savings if you are controlling centrifugal pumps. ABB have patented DTC which gives very accurate control if you require it.

I have just installed schneider 75kw as a freebee. Line reactor is separate.Its a hell of a lump. Not powered it up yet though i will let you know how easy it is to configure.

:thumbsup::thumbsup::thumbsup::thumbsup::thumbsup:


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## Lone Crapshooter

The VFD would be a good idea however a regular motor will not last on a VFD . A VFD rated motor is designed to tolerate the spiked and high yoltages that a VFD puts out. It is not uncommon for a 480 volt drive to put out 800 + volts. Anouther thing is the distance between the VFD and the motor If it is 100+ feet the wire insulation between the drive and motor become a issue. It is not a plug and play type situation.
LC


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## InControl

lukejenson said:


> Even tho it says KSB on the nameplate, it looks like a lenze nameplate to me.


Its the European standard for nameplates. They all look the same.


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## yindavies

I agree about the old motors not being invertor rated. Can you purchase new high efficiency motors. If you run these pumps on pressure control as stated the payback is huge. 

KSB are a pumps manufacturer. They will tell you if the motor is rated for the job.

I would only be concerned if the motor is over 100m from the drive. You can fit a du/dvt filter if longer.


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## acdrive

browningwgm said:


> Hello,
> 
> A little background on myself. I'm an active duty HVAC tech serving in USAF. I'm currently deployed to a location in Southwest Asia. I have been asked to look at an issue with a water distribution system. They have 8 45KW (60HP) pumps that are delta wound running 415 VAC 3 ph 50hz. There's 6 power leads going to the motor.
> 
> Motor data plate states
> 400 Delta 50hz
> 690 Wye 50hz
> 
> 460 delta 60hz
> 
> What I want to know is, can this motor be ran off a VFD? The current setup uses 3 contactors. At startup, the start and shorting contactors pull in. After a couple seconds, the shorting contactor drops out and at the same time the run contactor will pull in. This seems to be a pretty standard start sequence that I've seen on some larger chiller units before.
> 
> My goal is to run these pumps off a VFD to avoid constant start/stops that's occuring and wearing out our equipment.
> 
> If you need more info, please let me know and I can get it. Any help would be appreciated. Thanks.


run off? sorry. I don't understand.

Motor soft starter may be a choice


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## yindavies

Hi. I am not sure what the shorting contacting is doing. But because you have 6 leads going to the motor I will assume you are using a star/delta starting method. 

You can run most 3 phase motors with a VFD but if they are not invertor rated they could fail after a period with insulation breakdown or bearing failure. When ever possible I will fit a new motor with a non drive end insulated bearing. All depends on the application and wether you can afford the motor failure. Another thing is cable lengths and harmonics. Dont want to put you off but you need to be aware of these if you put allot of VFD,s on a network. These are small motors and I will assume cable lengths of less than 100m so you should be ok. Pay particular attention to earthing the motor and VFD.

I would not look at a soft start unless the customer demands one. When you have a VFD installed it is so flexible. You can run half speed, pressure control, level control basically its up to you how you control the water system. I would like to know what it is though as I may be able to offer more advise.

Basically disconnect the shorting and run contactor and connect the out going start contactor cables directly to the power VFD input and then VFD output directly to the motor. Connect the motor in delta at the motor. Now when start contactor energises it will put juice onto the VFD. You can either configure the VFD to run on start up or use a separate run relay. Like I said not sure what your application is. But using a VFD you can put a very slow ramp rate to protect equipment if so desired.

Try to use the VFD start interlock and connect it to an early break contact on the motor local isolator. This is good practise. Stops should not have changed as you have not altered the original start stop circuit.

Hope this helps.


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## scaledwithparameters

varmit said:


> Rob,
> A VFD is an easy conversion to this set-up. However, post #3 is incorrect about the motor connection: The motor must be connected in the Delta "run" mode. The drive leads would connect to motor leads U1, V1, & W1.
> Motor leads U2, V2 and W2 would connect together - as if the jumper contactor was pulled in at all times.
> 
> You could simplify the control logic quite a bit as the drive would only need a start and stop input if wired for 3 wire control. The speed reference, to the drive, I am assuming, would be based on system pressure.
> 
> One thing to look at, that can cause a problem, would be if the pumps pump up to a considerable elevation gain or have a potential to have back pressure. If you encounter reverse flow through a VFD driven pump you can get a "buss overvoltage fault" as the motor can become a generator and feed excess energy back to the drive. The fix, if this problem shows up, is to install a dynamic braking resistor connected to the "brake" terminals at the drive.
> 
> A line reactor is always a good idea on the line side of a VFD as the drive high speed switching can cause frequency increases to the distribution system back to the nearest transformer in the circuit.
> 
> While Wye-Delta starters are rare in the US, except for 100 HP and larger, they are still quite common on European (IEC) equipment.
> 
> I hope that this helps.
> Harry



This can also be resolved by (and should be) by a backwater valve (check-valve) only allowing flow in one direction...


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