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Six-Terminal Motor with VFD Connection

08/06/2009 4:04 AM

i have six terminal three phase motor 4kw .from terminal we can connect it in star or delta mode . but if i am using VFD three phase input 440 volt applied to vfd input then in output from the vfd the motor will be connected in star or delta mode ?

also in vfd range up to 5 h.p vfd input single phase supply 220 volt and o/p from the VFD 220 volt three phase ,then motor will be connected in star or delta ?

plz reply for my query .

atul

india

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#1

Re: six terminal motor with VFD connection

08/06/2009 4:22 AM

<...output from the vfd the motor will be connected in star or delta mode....>

Delta if there are six terminals on the VFD. Otherwise, star.

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#6
In reply to #1

Re: six terminal motor with VFD connection

08/07/2009 2:45 AM

"in delta mode it is 440 volt. motor in star it is 220 volt 50 hz motor" if i understand correct you are saying in delta connection the supply is 440v and in star connection it is 220v on the motor rating plate?

This is impossible and should be other way: delta = 220v and star = 440v.

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#2

Re: six terminal motor with VFD connection

08/06/2009 6:44 AM

What does the rating plate of the motor indicates?

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#3
In reply to #2

Re: six terminal motor with VFD connection

08/06/2009 6:57 AM

sir

it is showing 440 volt 50 hz motor

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#4
In reply to #3

Re: six terminal motor with VFD connection

08/06/2009 7:03 AM

No connection detail for the 440v on the nameplate? What brand of motor?

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#5
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Re: six terminal motor with VFD connection

08/07/2009 2:13 AM

in delta mode it is 440 volt. motor in star it is 220 volt 50 hz motor .

from D.T ,i have three phase 440 volt which is applied to motor terminal and connected the motor in star or delta .there is no internal star or delta connection .

it is stark motor (indian made ) .

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#7
In reply to #5

Re: six terminal motor with VFD connection

08/07/2009 4:36 AM

Have you got this the right way round, or have I miss interpreted it? The motor is delta for 440V and start for 220V?? Doesn't sound right.

On the name plate, most times, there will be the motor voltage and a symbol ie. 440Δ for delta, or 415/240 (for here in Oz) which means the motor is wired in delta for 240V or star for 415V.

Anyway with your application you need to wire it as a 440v supply as that is the VFD's output voltage

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#8
In reply to #7

Re: six terminal motor with VFD connection

08/07/2009 4:39 AM

And furthermore, with a single phase 240v? input VFD the output is 240v? three phase, so you would normally wire as delta.

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#9
In reply to #8

Re: six terminal motor with VFD connection

08/07/2009 6:07 AM

i am agree from your tips .thanks , it is connected in delta mode if three phase supply is 220 volt and if supply is 440 volt in three phase then it will connect in star mode .

i am confused if i am using single phase supply(220 volt ) applied to vfd input and from vfd o/p is 220 volt three phase then motor will connect in star or delta .

if i am using three phase input 440 volt applied to vfd input and o/p from the vfd 440 volt then motor will be connected in star or delta .

in case of vfd both option is present .but in both option torque will be same from the vfd o/p ?.

which one is best vfd for my application .if ACC TIME is 1.5 sec and DEC time is 1.5 sec and min and max freq is 10.5 hz to 33hz .

plz reply .

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#12
In reply to #9

Re: six terminal motor with VFD connection

08/07/2009 7:36 PM

Atulsaxena,

The ratio of voltages between delta and star connection should be sqrt(3). I am assuming you use the colloquial denomination "440 - line-to-line (phase-to-phase) and 220 - line-to ground/earth". The correct pairs are 220/380V respectively 254/440V.

A motor that is designed for running in delta connection is meant to have applied at the one winding the higher voltage (in this case 440 V). If you apply the lower voltage (220V) at the same frequency, the drawn current will be lower, as well as the developed torque. So you cannot load up the motor up to its rated power, but for testing you will not damage the motor windings.

If the motor is designed for star connection, the voltage applied to the winding is the lower one (220V - phase to ground) and if you connect it to the higher voltage (440V) (at the same frequency), it will overheat and finally blow the overcurrent protection of your circuit.

You cannot apply 220V ( single phase) at the VFD input and get a 3-phase output, unless you are using a rotary converter.

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#10

Re: Six-Terminal Motor with VFD Connection

08/07/2009 6:10 AM

4kW motor should be about 8 to 9 amps full load current, no load current should be about 4 to 5 amps.

VFD output is 400V at rated Hz (50?) so the motor should be connected for 400V, look on nameplate to see if this is delta or star connection (normally delta).

If no motor nameplate, connect in STAR and run to full speed at no load (on mains or 400V VFD) and check motor current by the VFD readout or current clamp. If its very low, like 1 amp or something, you then know the connection should be DELTA as the no load current is far too low showing reduced fluxing current as you are applying 400V to the 660V connection.

If you have a 220V VFD then you should connect motor for this connection IF its available. If your motor is 400V Delta / 660V STAR then you cannot do this.

In this case you can programme the VFD for 220V at 29Hz (on 50 Hz winding) and this will give constant torque to this speed on the 8-9amp winding. Thereafter, you will have constant power only at the reduced level limited by your voltage i.e. 1/√3 of 4kW = 2.3kW. If this is enough for your application - OK.

Hope this helps!

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#11

Re: Six-Terminal Motor with VFD Connection

08/07/2009 7:45 AM

"which one is best vfd for my application .if ACC TIME is 1.5 sec and DEC time is 1.5 sec and min and max freq is 10.5 hz to 33hz ".

Not trying to be nasty, but I think you should get help from somebody with the necessary experience on vsd's and motors.

If you want to decelerate a load with a motor driven by a vsd in 1,5 seconds chances are that the drive will trip as a result of a over voltage on the DC buss of the vsd. For this you require a resistor connected to the DC circuit. Is your vsd equipped with this function (to connect a resistor)?

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#13

Re: Six-Terminal Motor with VFD Connection

08/17/2009 9:06 AM

A six terminal motors wire as delta-star purposely for a reduced voltage automation starting comprising with two magnetic starters (y-delta) and a timer plus OL. If we conside the six-terminal leads out motor in conjunction with manufacturer's nameplate rating @240/415V, meaning initially it starts at wye @240V then at few seconds to delta so called reduced voltage y-delta starting. Thus theoretically, V(wye)phase voltage = 240Vx sq. root of 3= 415V(delta).

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