One way to do it is to connect a 'braking resistor' to the drive which, when the VFD is configured to know it is there, will help it slow down faster. The manual will (usually) have a list of suitable sized resistors in it somewhere, along with the settings you need to change.

The braking resistors are typically low resistance, high wattage, ceramic units (mine took a 100ohm 300W resistor).

Vic, my inverter has a 'ramp up/down' setting which determines how fast the spindle gets up to speed, and slows down. It's not braking as such, just the time taken to go from selected speed to zero. Yours would appear to be on page 5-3 of the manual, called decel time (1-10 and 1-12) The default appears to be 1 sec, so it may have been altered. Chapter 4.4 shows how to alter the parameters. Without the unit in front of me, I can't help you on changing the settings, but if you work through the guide 4.4 you should be able to get to Group 1 (Basic parameter), then item 10 (decel) and set the value to 10 (=1second)

There is a section on braking resistors, but you may find that decel solves your problem. If all else fails, you could try a factory reset to get accel and decel to be 1 sec

Rgds,

John

Vic, just think of us who 50+ years ago were turning wood, no fancy VFD drives then!!

Apart from being able to set the speed carefully (and low) when roughing, I cannot see the need for a VFD. Perhaps Jason has a view?

Hi Vic,

Just to try and enlighten you on what your vfd is doing for you and help you to get the best from it. The supply is AC and is rectified to give a high voltage DC supply from which 3 phases can be created at any frequency you need for the speed you demand. The problem with trying to slow down quickly is the output stage of the inverter acts as an input back to the DC supply which will push the voltage higher, if the drive detects this it will try and dump this to an external resistor if fitted but if not fitted it will shut the drive down to protect itself. It looks as though your drive has a parameter 1-15 that can be set to slow the drive as rapidly as possible depending on the load, it may be worth trying this out as if you choose a fixed slowdown ramp it will have to be for the worst case scenario which will be the heaviest or fastest job you do. The great thing about VFDs is that they can be made to slow faster than a simple motor drive which unless a mechanical brake is fitted will always coast to a stop. With a resistor fitted to absorb the energy from the machine some quite savage rates of braking can be achieved. If the nose of the lathe takes screw on faceplates and chucks this may try to unscrew the faceplate when braking (just a possibility)

Mike

That lathe does have a threaded spindle so active braking might not be a good idea.

Russell.

Hi ega, I do not have first hand experience of the teco mincon drive but I had a little browse of a manual on line and as David mentions above it would appear they use the DC injection braking system, this might explain your difficulty in finding what to do with the braking resistor as this type of braking would not use a resistor. There are a few parameters to set to give the braking effect required for your application. DC injection can give a very powerful effect and is sometimes used as safety brake on things like drilling machines where an almost instant stop can be achieved. Used as an emergency stop for operator protection puts quite a high mechanical stress on the machine but a much milder effect can also be used.

Mike

I had a quick look at the online manual for the Delta VFD-S unit. Page 5-3 shows that the default setting for parameter 1-10 (the deceleration time) is 10 secs. which is quite a long time when you just want to stop the motor. Changing this parameter to to a lower value (2, say) should improve your perception of the slowdown time. If the time you choose is too low then the VFD will "trip out" with an overload error and you will have to reset it before you can continue. Fitting a braking resister will allow you to choose a lower value without tripping out, but you must choose a resister that matches your VFD power rating. My guess is that a 2 sec decel time will probably work OK.

Page 5.3 in the online manual states quite clearly Factory Default for Acceleration and Deceleration is 10.0 seconds, yes Ten secs

I think KWILL's interpretation is the correct one.

Les.

If you look in the manual at Section 5.3, Group 8 (special parameters), there are settings for DC brake (aka DC injection). This doesn't require the braking resistor to be fitted and can give a useful improvement on decel times. You end up dumping the kinetic energy into the rotor but that really won't be an issue for an application like this with so little inertia. After all, the rotor "winding" of an induction motor sees a fair bit of current / dissipation under normal load anyway – it's how they work.

Have a go at playing with the settings. You won't damage anything if you've set the name plate parameters already and it can give quite a useful improvement. This setting is an additional function on top of the normal decel.

The limitation on decel is the DC bus voltage rising if the regen energy exceeds the losses in the system. Without a braking resistor circuit, the VFD can only inhibit its operation to protect itself if you try to decel too quickly.

Murray