what is VS coupling or VSD coupling ? thanks

[munzir]

what is VS coupling or VSD coupling ?

There's a 3 phase AC motor and connected with it there are four(4) wires out of the assembly where for 2 wires control supply of clutch is provided via card & 2 wires for tacho for which control supply is from the same card .......

the card has single phase AC input 220 Vac ........... there's a 10K pot when the pot is off the shaft is stationary and as we rotate the pot the shaft increases its speed (also when the pot is off there are no voltages on the clutch via card and as it rotates dc voltages out of the card increases upto 95 Vdc) and when we bring it back the motor & hence the speed of the shaft decreases to almost zero .......

the 3 phase motor is about 2.2KW

For what purpose tacho is used in this design & process ?

the resistance that i measure at the motor terminal for clutch is 23 ohms & for tacho is 63 ohms but the problem is that the motor & hence the shaft is not stopping neither the speed of the motor & hence of the shaft is not slowing down (though i fully off the pot i.e. take it to the zero position of the pot) ...... and it accelerates to its full speed as i just rotate the pot a point or little more ......

what might be the problem & how to resolve the issue ?

thanks

 

[kak111]

If the hardware configuration is as shown in figure,
and no hydraulic oil is used in coupling.
I would guess that this device is
Eddy Current Variable Speed Drive (Eddy Current Drive).

An eddy current drive consists of a fixed speed motor and an eddy current clutch. The clutch contains a fixed speed rotor
and an adjustable speed rotor separated by a small air gap. A direct current in a field coil produces a magnetic field that
determines the torque transmitted from the input rotor to the output rotor. The controller provides closed loop speed regulation
by varying clutch current, only allowing the clutch to transmit enough torque to operate at the desired speed.
Speed feedback is typically provided via an integral AC tachometer.

Eddy current drives are a type of slip controlled drive. Slip controlled drives are generally less efficient than other types of drives.
The motor develops the torque required by the load and operates at full speed. The output shaft transmits the same torque to
the load, but turns at a slower speed. Since power is proportional to torque multiplied by speed, the input power is proportional
to motor speed times operating torque while the output power is output speed times operating torque.



Tacho is for speed feedback of output shaft.
Think it simlified that way pot.meter gives set value to controller and
tacho gives inverted set value.
When these two values are balanced, set value is achieved in output shaft speed.



KAK

 

[kak111]

This article describes the basic eddy-current drive.
Principles and control

**broken link removed**





So the problem is
when set-pot.meter is zero output shaft is not stopped.
when set-pot.meter is moved a bit from zero position, output shaft runs max. rpm
When pot.meter is out of circuit output rpm is zero...
When the control wires to eddy drive is taken out output rpm is zero...
When pot.meter is zero and the control wires to eddy drive is connected again output rpm is not zero...
Is that right ?? ....
Is any load connected to output shaft when you do these tests.

Once again : tell me manufacturer and type of drive and controller.

KAK

 

[munzir]

This article describes the basic eddy-current drive.
Principles and control

**broken link removed**


View attachment 68186


So the problem is
when set-pot.meter is zero output shaft is not stopped.
when set-pot.meter is moved a bit from zero position, output shaft runs max. rpm
When pot.meter is out of circuit output rpm is zero...
When the control wires to eddy drive is taken out output rpm is zero...
When pot.meter is zero and the control wires to eddy drive is connected again output rpm is not zero...
Is that right ?? ....
Is any load connected to output shaft when you do these tests.

Once again : tell me manufacturer and type of drive and controller.

KAK

yes you're right ....... whether loaded or unloaded same behavior & same fault ......
Is the clutch connected to the field winding ?
Is it a DC drive ? Or can it we say a DC drive ?

This drive is connected with the rewinding machine (that is used to rewind the packaging film) .......

When i swapped in 3KW same drive whose resistance (of the wires where clutch is connected) is about 29 ohms & for the wires where tachometer is connected is about 177 ohms ..... then the motor & hence the speed of the shaft is controlled and it works fine .......

What are the symptoms if tachometer is gone bad ? How to test the tachometer ?
Is tachometer connected to the stator winding ?
What are the symptoms if clutch is gone bad ? How to test clutch ?

thanks

 

[kak111]

Is the clutch connected to the field winding ?
Is it a DC drive ? Or can it we say a DC drive ?

Keep in mind that I have not seen this device, and I do not know the type of equipment in question
I assume that this is an eddy current drive.

Read post #2 once more....

An eddy current drive consists of two main parts
- 1. a fixed speed motor. ( usually 3-phase induction motor )
- 2. an eddy current clutch.

The clutch contains a fixed speed rotor , ( input shaft rotated by motor )
and an adjustable speed rotor separated by a small air gap , ( output shaft for load )

A direct current in a field coil produces a magnetic field that
determines the torque transmitted from the input rotor to the output rotor.

Eddy current drives are a type of slip controlled drive. ( or better to call slip controlled clutch )

What are the symptoms if tachometer is gone bad ?

in post #2 you see picture of feedback principle via tachometer.

if tacho fails then
-when set value from pot.meter is zero output is zero
-when set value has small positive signal, output shaft runs full speed,
because there is no negative feedback to compensate set-value.

How to test the tachometer ?

Tachometer is normal ac- or dc-generator.
You can rotate tacho with (eg.) drilling machine and measure output voltage.
This output should be linear function to rpm.
In tachos nameplate is given output voltage value / 1000rpm.
If tacho is dc-type , check rotor brushes.

Is tachometer connected to the stator winding ?

Tacho runs with output rotor. ( output shaft )

What are the symptoms if clutch is gone bad ?

If current coil is broken, output is zero.
If current coil is partially grounded, full output is not achieved or control fuse trips.
Input or output rotors mechanical failure usually cause a mechanical locking from input to output or to frame.

How to test clutch ?

Run with given control current or voltage value , measure torque and rpm.
Compare measured values to values given in manufacturers data.

 

[munzir]

thanks a lot for your precious platinum reply

How to set up this ? " You can rotate tacho with (eg.) drilling machine and measure output voltage. "

Is it mean that as output voltage increases rpm increases & as output voltage decreases the rpm also decreases ? " This output should be linear function to rpm. "

Is the ratio of output voltage & rpm given in the nameplate of the tacho ? "In tachos nameplate is given output voltage value / 1000rpm. "

thanks very much again

 

[phatcreators]

How to measure & check out the rotor brushes ? For this purpose measure the resistance with DMM and what should be the perfect value ranges ???

 

[kak111]

How to set up this ? " You can rotate tacho with (eg.) drilling machine

This is if tacho is separate component.
If tacho is integrated to output rotor, rotate shaft with hand and measure output.
Linear output function is the case when rpm doubles, voltage doubles too...etc...

Usually the ratio of output voltage & rpm is given in nameplate.


How to measure & check brushes ?

IF DC-TACHO IS USED
Take the brushes out from tachometer and inspect the condition visually.
the shape and length will vary by type.
Clean and check that brush can move freely in its holder.

Similarly, the winding resistance varies by type
Check rotor collector , check that every coil windings have same resistance

ROTOR BRUSHES
-look above...

 

[munzir]

Measure output from where ? from the card ??? where the wires of Tacho are connected to the card ........

and voltages should be increased when increasing the rotation & speed of the shaft ????

 

[dineshdeshmuk]

1) Can we use a frequency inverter to control this eddy current drive ? Instead of a VS coupling .........

AC to DC OR AC to AC frequency inverter .....

2) Can we use a frequency inverter to control this eddy current drive ? Instead of using control unit (as drawn in post # 2 & diagram 1) .........

AC to DC OR AC to AC frequency inverter .....

Help me

 

[phatcreators]

Check rotor collector , check that every coil windings have same resistance ....

What is rotor collector ? How can we check it ?

just check out the resistance of the tachometer' winding with DMM and they should be same ........

How much tolerance is acceptable ?

 

[kak111]

Measure output from where ? from the card ??? where the wires of Tacho are connected to the card ........

You can measure at any point where is a direct electrical connection to tacho terminals .
If the symptoms are such as described,
and if you have a DC-Tacho
the first thing to do is : inspect and clean the brushes and the tacho collector.

1) Can we use a frequency inverter to control this eddy current drive ? Instead of a VS coupling .........

Not direct, additional speed and torque control system is needed too.
Original Eddy current clutch in machine keeps stable controlled torque on output shaft.
Drive motor in Eddy drive runs fixed speed and eddy clutch keep torque and speed in set-value.
Remember that Eddy current drive is slip controlled drive.

2) Can we use a frequency inverter to control this eddy current drive ?

No , eddy current clutch is DC-current controlled device.
Motor speed is not controlled.

What is rotor collector

If this drive has stationary field coils, there is no brushes or slip rings.
Look picture in post #3.

But if drive is brushed type , there is brushes or slip rings in rotor.
Look pict. below...