I can confirm what Mike said about the older VFDs (roughly, pre-1990) leaving the output terminals hot even when there was no motor attached. I've got an old 20-HP Allen-Bradley 1333 Series A that couldn't care less if the motor is there or not. On the other hand, there's lots of things that VFD can't do that are commonplace features in more recent units.
If you run multiple motors off a single VFD, be careful to include overloads in each of the motor circuits. Whatever your position is on multiple-motors-per-VFD, failing to protect each individual motor is a recipe for disaster. For most of the retrofitting being discussed in this thread, the overloads are not a big problem: Assuming that you'll be using the existing contactors as the switch element between the VFD and an individual motor, just reuse the heaters that are already attached to the contactors. If the retrofit includes a voltage change (e.g. 440 to 240, etc.) the heater elements will need to be changed out.
I really can't speak to the question of whether switching multiple motors in and out of a VFDs output circuit is destructive to the VFD. I've never designed a system that used this idea. I suspect that the issue may be more of reliability and time-to-fail than an immediate melt-down of the VFD. I agree with Mark Rand's comment about reflected voltage, but there are also switching transients to be considered: possibly their cumulative effect shortens the life of the output section? Also, the drive's output is designed to initially flux the motor at very low voltage. If you start the motor via a contactor where the VFD is already producing 60Hz at full voltage, surely the start-up "surge" current passing through the output section is much higher?
If we neglect the reliability issue, then it seems clear that the cost basis is less for the case where a single VFD is powering multiple motors, especially since in this thread you already have the contactors and overload heaters you need. You would have to give up those features that are "personalized" to the motor or process, such as acceleration, deceleration, etc. but if the VFD is only servicing the small motors then this probably doesn't matter much.
Fractional horsepower VFDs have fallen so dramatically in price over the last decade that, for me, multi-motor setups are not worth the worry.
I hate doing maintenance. I'd rather build it once and have it run forever. Modern VFDs can really "baby" your motors, and to me, that alone is worth the price of admission.
Your mileage may vary!
I'm doing my best to follow all of this. Mike, I don't see timing problems with this arrangement, but maybe you were referring to systems like this in general, rather than this specific plan. What is a PB station? I like that carriage dial indicator on your lathe. Did you make the mount? What is the other indicator at the tailstock for? Pete, on my schematic the run/stop signal enables all three VFDs. It is only asserted when then spindle runs, so the speed change motor is interlocked. Jay, I will take you up on your kind offer to show me what you have done. I'm trolling ebay for VFDs...
I was describing systems like this in general, and in more particular a fairly minimalist approach to the problem that I had designed for my own HLV-H. I deliberately left all the existing contacts and functionality in place, relying on timing adjustments (and one relay addition to ensure adequate delay) to control the run/stop function in the VFD after all the contactors and cam switches had made or broken their contacts and stopped bouncing around. From your description, you were going to employ a more drastic redesign/rewiring to achieve the same ends, and it sounds as though it would work fine as well. I was trying to make it bullet proof so I wouldn't have to remember not to throw certain switches at certain times. I eventually abandoned the project as not the best use of what little time I had during that period, but I heartily encourage you to follow through with your approach and get the satisfaction of seeing it all work! [img]tongue.gif[/img]
A PB station is a Push Button station - the red/green button box under the lip of the coolant tray to the right of the carriage in the photo above.
The Hardinge H-HD1 carriage dial indicator is more fully described at http://aafradio.org/garajmahal/Hardinge_H-HD1.html , including dimensions if you wish to make your own.
I'm afraid the other indicator is just parked there to get it out of the way - it's the "other" Hardinge HLV-H indicator mount that has a micrometer head allowing adjustment to tenths. It's a pain to use, however - it mounts on the bed between the headstock and the carriage, restricting X axis travel in some setups. It also has an annoying habit of becoming a swarf "dam" as the swarf accumulates. I've used mine only a few times to get the accuracy it provides, but the H-HD1 stays on the lathe pretty much permanently.
I am new to this forum and stumbled upon this post, which directly applies to what I am trying to do.
I have a late 50's HLV-F, which is a narrow bed version, but it has the power variable speed setup(not the manual crank like the older -B).
I also have the extra complexity of the machine is setup for 440V.
My plan before reading this post was a setup like Dave (LowEnergyParticle) described.
Dave, I was wondering if you had a picture of your setup?
I want ALL of the levers and buttons to work like stock from the outside, but I was just going to pretty much gut the control box and start over. After reading a few posts on this forum and talking to some local Hardinge people, I am a little concerned that this will be considered heresy. Should I be worried about removing all of the original contacters and heaters?
I have two 440 VFD's, one for the main spindler motor and one for the motor that drives the variable speed system. My lathe no longer has a coolant pump. I purchased a 2KV single phase transformer that am mounting inside the base of the lathe that will feed the VFD's and brake coil.
Any help would be appreciated.
I recently completed converting two Hardinge tools to VFD power yet maintaining the original control features. One is a TL, the predecessor of the HLV, and the other is a UM tool room mill. The latter incorporated a single phase transformer to boost to 440V with the VFD converting to 3 phase.
In both cases, I essentially wired the VFD in the original wiring system right after the main power contactor. To enable the use of the control handles for high-off-low, I made a small cam and installed it on the drum switch shaft, in a manner that when the switch is fully turned in either direction a microswitch activates the VFD through its control circuit. An important feature of this approach is that the micro switch is positioned such that all the drum switch contacts are closed before the cam activates the VFD.
Although the conventional wisdom is that no switches should be downstream of the VFD, my setup has the fwd-off-rev and the high-off-low switches after the VFD. Neither gets switched with the VFD on so I don't have a problem.
I don't use the high-low lever as a rule, rather keep it in high and use the VFD to vary the speed.
The obvious downside to my set up is that I must remember to not switch quickly from high to low or from fwd to reverse without allowing the machine to stop. Being a one-person home shop, this is no problem for me.
The only external evidence of the VFD is a speed control knob which remotes to the VFD.
I did it this way not so much to remain close to the OEM wiring, but to simplify the installation. In the six months I've used the machines, the setup has worked flawlessly.
Just to add another to the list
This is how I've converted my UK 440v 3ph HLV-H to single phase.
I used a Siemens MM150 (2hp) 440v 3ph inverter running from a 1KVA 240-415v step-up auto-transformer
In order to keep the original Low/Stop/High control lever without fear of blowing the VFD, I have completely rewired the circuit so that the VFD's output is only changed when the motor is stopped. To do this, I've used the pair of interlinked contactors that were previously used to enable the speed adjust jack motor and a simple relay circuit.
The coolant pump has its own 240v VFD (the dual voltage pump motor was rewired to 240v)
The speed jack was to be controlled by another 240v VFD, unfortunately the jack motor on my HLV is single voltage (440v) so I've had to use a couple of contactors to control it instead.
I'm happy with the way it works.
YouTube - Hardinge HLV H motor control
Thanks for the link to Airlink transformers, looks like they've got just the one that I need
I happily DOL switch the motors on my J&S 1400 grinder after the output of my VFD. but the VFD is rated at 23KVA and 650V, so isn't stressed by the abuse that I give it. The plan is to wire it in so all of the three phase machines are fed from it (Grinder, HLV, Beaver mill, J&S drill). If it blows up, I've lost £10
If it goes bang, it'll be a big one