2900rpm fan running at 1000rpm

James Nolan

I have a 3 phase 2900rpm fan that is DOL DElta that is connected correctly according to the manufacturers plate but but will only run at approx 1000rpm.
The voltage is right. Ant suggestions

cambruzzi

If voltage is right it could just be a defective motor...

micromind

A bit more info is needed;

1) Is this a 50 HZ system? I bet it is, since a 60 Hz 2 pole motor is around 3450 RPM, and a 4 pole is 1725.

2) Is this a two speed motor? How many leads does it have? What are they labeled?

3) Is this a dual voltage motor? What is the supply voltage?

If you can give us a bit more info, we can probably help.

Rob

James Nolan

Hope this is enought!

J. V.

James, So what are the answers to Robs questions? Rob is very knowledgeable with motors. Please do not waist the time of the professionals that are trying to help.

jbfan

He answered the questions JV.

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Sliver

Here were his answers, I didn't see them right away either...

1) Is this a 50 HZ system? I bet it is, since a 60 Hz 2 pole motor is around 3450 RPM, and a 4 pole is 1725.

Yes its 50hz

2) Is this a two speed motor? How many leads does it have? What are they labeled?

6 terminals;U1,V1,W1 &U2,V2,W2

3) Is this a dual voltage motor? What is the supply voltage?

Single voltage, 400volts between phases

frenchelectrican

For 6 lead { wires } 3Ø motours there are few diffrent verison of connections depending on if it have DY Delta start Wye run or Wye run with two speed format ?

If you set up for DOL Delta connection here the connections.,,

L1 - U1W2

L2- V1,U2

L3- W1,V2

But double check the motor nameplate to verify it and some reason if you are running very low speed then you got one of the connetion not hook up right or have a open delta it will affect the speed and performace.

Merci,Marc

James Nolan

Thanks Marc,
I tried a few variations on the delta and found that the manufacturer had labeled U1 and U2 the wrong way around.Once I got that off it went at 2900 rpm.SO I HAD TWO PHASES TRYING TO ROTATE CLOCKWISE AND ONE ANTICLOCKWISE HENCE THE APPROX. 1000RPM
Moral: Don't always trust the manufacturers quality control.
Thanks:
JAMES

AllanJ

OT: This is very frightening.

What if the motor burned out? Would the manufacturer accept responsibility?

Do we as consumers or electricians need to perform tests before completing the installation of products?

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J. V.

Allan, I totally agree with you. I have wired countless motors and have never found a motor marked wrong from the factory.
I have found many motors marked wrong by the second or third party.
Fortunately we can make certain if we have a way to measure continuity. A six lead motor can be labeled in a flash.

micromind

I've been out of town for a few days, so i didn't get a chance to follow up on this one.

So far, I've seen 3 motors and one generator mis-marked.

One motor was a NEMA frame (leads are marked T1, T2, T3, etc.), and it was mismarked from a rebuild shop.

The two other motors were IEC frames (leads marked U, V, W,etc.) and both were new.

The generator was used, and looked like it had been marked by other than the factory.

Whenever I start a 3 phase motor for the first time, I always measure current. I'm looking to compare actual current with nameplate, and balance. Swapped leads will result in a huge imbalance. Two of the leads will have very high current, while the third one will be about normal. I also measure current around all 3 wires. If this reading is more than 0, it indicates a ground-fault.

In case of a severe imbalance (this would have been my advice to the original poster) would be to measure current in individual motor leads. Each lead should be about the same. If two of them that compose a winding are way higher, swap them and see what happens.

Rob

James Nolan

Thanks for that but because the fan motor was small 1.25kW and as the power goes up with the cube of the speed it was hard to tell the current exactly against the nameplate as it never achieved full speed hence current low.All 3 phase were different at time of measurement, which would correspond to say phase 1 trying to overcome the reverse torque applies by phase 3 and phase 2 was just continuing with the rotation while phase 3 was trying to reverse phase two hence more current.
James
james

mahdiking000

the 3 p fan rpm control by 2 system:
1- takho or magnet sensor
2- current on one by one phase
your fan what system?

James Nolan

Fan motor is synchronous to 50 hz.
The speed readings were made with a laser tachometer.