The VFD on my lathe has burnt out. I have found two good replacements; they are essentially identical except that one has a EMC filter and the other will accept a braking resistor. Are either of those necessary?
I see that as a setting. What does ramping down actually do? The VFD recommends a setting of 5 seconds.In general, a braking resistor is needed in situations where there is an overhauling load for a significant portion of the drive's duty cycle. An overhauling load is basically an aiding load as opposed to the normal situation in which the load is opposing the drive. An example of an overhauling load would be a heavily loaded conveyor going downhill on a steep slope. In that kind of situation, the load is driving the motor which means the motor becomes a generator that is dumping energy back into the VFD. A braking resistor would be needed to dissipate that energy, converting it into heat. This isn't a situation that would be encountered in woodturning other than a few seconds when ramping down a very heavy inertial load (very large diameter and very heavy, more than 100 pounds). If you are concerned, the easiest solution would be to increase the deceleration ramp time.
What difference do you see in stopping with a bowl, with and without the resistor? Is it 15 second compared to 5 seconds, or 120 seconds compared to 5 seconds?Here is some Google help; https://www.manufacturingtomorrow.c...-how-should-i-select-a-braking-resistor/15756
EMC Filtering For industrial Applications - Roxburgh EMC
EMC (Electromagnetic Compatibility) filters are used to ensure that electrical and electronic equipment does not generate, or is not affected by, electromagnetic disturbance.www.dem-uk.com
You will like the braking resistor if you turn large bowls. My Oneway has a switch to turn the resistor circuit on and off. The only reason I've heard of EMC filters in a hobby shop is hearing static in the shop radio. I don't think they are expensive accessories.
If I am turning a huge blank like 18"-22" diameter, and forget to set the braking to slow, it will trip the VFD when I hit the stop button. That is when I'm checking progress of the outside roughing and the interior has not been touched. I have to press a reset button for the lathe to run again. If I was to guess on the time difference, I'd say 10 seconds vs 30 seconds.What difference do you see in stopping with a bowl, with and without the resistor? Is it 15 second compared to 5 seconds, or 120 seconds compared to 5 seconds?
The EMC filter is probably unnecessary; apparently they are required by the EU.
When the VFD receives the stop command it decelerates or ramps the motor down to zero speed and then shuts itself down. If you have an emergency stop that disconnects power or you just loose power, then it would coast to a stop and probably take more then 5 seconds to come to a stop.I see that as a setting. What does ramping down actually do? The VFD recommends a setting of 5 seconds.
So it stops faster if you ramp down the power than if you simply stop the power? That is counter intuitive, but I'll take your word for it.When the VFD receives the stop command it decelerates or ramps the motor down to zero speed and then shuts itself down. If you have an emergency stop that disconnects power or you just loose power, then it would coast to a stop and probably take more then 5 seconds to come to a stop.
Refer back to Bill B's reply! The brake resistor is needed only if you have an overhauling load or try to stop in too short a time and on a lathe as long as you go with the 5 second deceleration recommended you should not need a brake resistor. I have been using VFD's on wood lathes for 30 years and I have never had a need for or had a brake resistor.So it stops faster if you ramp down the power than if you simply stop the power? That is counter intuitive, but I'll take your word for it.
Do that eliminate the need for a brake resistor?
What difference do you see in stopping with a bowl, with and without the resistor? Is it 15 second compared to 5 seconds, or 120 seconds compared to 5 seconds?
The EMC filter is probably unnecessary; apparently they are required by the EU.
So it stops faster if you ramp down the power than if you simply stop the power? That is counter intuitive, but I'll take your word for it.
Do that eliminate the need for a brake resistor?
Thank you. My old VFD came with a resistor, and since it was a cheap one, I assumed they were necessary. Someone on line said that the cheap ones might come with a resistor but the terminals aren't connected to anything. I checked mine, and sure enough, the terminals aren't connected to anything.The casual observer wouldn't see any difference in stopping with or without the resistor. The difference is that the stored mechanical energy has to go somewhere when stopping the lathe. If the VFD uses a braking resistor then that's where the energy gets dissipated as heat. If there isn't a braking resistor then the energy is dissipated in the motor windings and VFD electronics as heat. For a woodturning lathe, unless the VFD manufacturer says you must have a braking resistor, then in all likelihood, you don't need it. The exception would be if you are turning massive tree trunks and stopping frequently. Even then it would be better to just cut power and let the lathe free-wheel to a stop. Otherwise, you would need to make sure that the chuck/faceplate doesn't unscrew during braking. Many years ago, I was quick enough to catch a heavy spinning chunk of wood before it hit the floor. This primal instinct to catch falling things isn't always a good idea, especially if they are heavy and spinning. Now, I just hit the emergency stop button if there is any possibility of the chuck unscrewing when stopping.
In the US, the FCC is the regulatory agency that sets what is known as Part 15 requirements for conducted and radiated interference. Theoretically, this would apply to lathes with variable frequency drives. There are some exceptions for industrial equipment and it is bending the rules a bit to apply it to consumers, but the ultimate responsibility for insuring that the lathe isn't causing harmful interference lies with the end user.
Actually, this is perfectly intuitive ... that is, if you know how an AC variable frequency drive works. Think about your bench grinder. When you shut off power, it slowly coasts to a stop. My bench grinder takes 1 minute 45 seconds to wind down. The speed of the VFD-controlled three-phase motor on your lathe is controlled by the frequency, not by power. This means that the motor speed is in lockstep with the frequency that is applied to it. So, if the VFD ramp-down time is 5 seconds from full speed to complete stop, this means that the frequency of the current to the motor is ramping down from 60 Hz at the rate of 12 Hz/sec.
Why on earth would they wire them in if they are just for show?
Very, very true. I have a deep 6" scar across my thigh to remind me. I've never been curious enough about physiology to want to see the inside of my leg like I did that day.Many years ago, I was quick enough to catch a heavy spinning chunk of wood before it hit the floor. This primal instinct to catch falling things isn't always a good idea, especially if they are heavy and spinning.
That is a good thing best to leave it alone unless you want to increase the deceleration time. The VFD is protecting itself and likely preventing the possibility of the chuck unscrewing.On my General lathe when I'm turning something more than 50 pounds it will trip the VFD overload when I hit the off switch. Always thought I would re-program the VFD but never have. I just slow the speed a little before hitting the off switch. Don't turn that much over 50 pounds anyhow.
On my General lathe when I'm turning something more than 50 pounds it will trip the VFD overload when I hit the off switch. Always thought I would re-program the VFD but never have. I just slow the speed a little before hitting the off switch. Don't turn that much over 50 pounds anyhow.
Personally, I would just reuse the old one, since your lathe manufacturer thought one would be of benefit, and not change the parameters. Braking resistors are simple devices that shouldn't wear out, AFAIK. If necessary, they can be had online for $30 or so.