VFD motor connections
Due to visibility and space restrictions, I want to wire a pigtail up to my motor assembly before installing it into my 10EE. The wiring tag has a diagram on it that I am not familiar with which is pictured below. Since this motor is designed to be run with an inverter, is this last diagram the one I want to follow. Also, the other picture shows wiring leads for a thermostat circuit. Since I haven't picked out a VFD yet, I was wondering if most control units will have a connection for these two leads. Sorry, but it won't let me into the attachment box until posting this. The pictures will be in the post below.
VFD motor connections
The first diagram is simply showing the motor's schematic in NEMA form.
You would still select the voltage in the same old way: input to T1, T2 and T3; bond T4, T5 and T6 together and insulate; connect T7 to T1, T8 to T2 and T9 to T3.
The diagram also shows the internal protection, one for each winding, and all in series.
These should be taken as series elements to be placed in series with the protective input to your VFD, assuming such a connection is available, or in series with the "three wire control station", such that if the motor overheats the VFD is commanded to shut itself down.
Most, if not all VFDs either have direct connections for a thermostat circuit, or one of the "multi-function" inputs can be programmed to accept the thermostat input. The thermostat circuit could be part of a series E-stop chain.
The Hitachi SJ200 has connections for the thermo switch, which would then trigger an overheat fault code. If connected in series with the control wiring, you would not know the overheat fault, just that the machine would not start, then after a few minutes it would start. That could drive you Nuts is
Now that I'm looking for a vfd, I need some suggestions from those of you who have done a 10EE conversion. I would like to keep my original Forward-Stop-Reverse switch, my original speed control knob, the original start and stop buttons to power up the unit and if possible the electrical block switch in the spindle lock. In an earlier post, "the real Leigh" responded and it sounded as if he was able to maintain these original functions. Perhaps he will respond to this and give me some more details about his vfd choice and any of its good or bad points. Also, "WILLI06907" stated that he used a sj300 but had better results with a Square D. I would appreciated hearing some of his recommendations on units he has had experience with. I'm kind of "electronically challenged" so I'm eager to have anyones input into what choices are available. One other function that I would like to have is braking. Thanks
I've got a Hitachi VFD in my EE, and all the features that you desire, plus I also added an apron mounted mounted start-stop lever. The headstock lever is primarily used as directional control. Like you, I'm electrically challenged, and my friends wired it up for me.
The braking resistors are an external add-on.
I see where some people have mentioned having encoders on their motors. I have the extra keyed extension on my motor tail end. What is the advantage and the purpose of this type of setup?
"What is the advantage and the purpose of this type of setup?"
Full closed loop control, which is what the encoder provides, allows control of the motor's torque all the way down to stall.
Simulated closed loop, which is what the sensorless vector drive attempts to provide by using a system of complex equations, allows control of the motor down close to stall, but not down to stall.
On some dc motor retrofits, an encoder was mandatory to detect field loss, otherwise the drive could not provide field weakening.
An encoder within the system is a good thing, but it is not required for many applications.
At a minimum, you want a "sensorless vector" drive. Any name-brand one of those will give the low-end torque you need, with appropriate tuning. In addition, any name-brand one can be programmed to use your existing For/Stop/Rev switch, speed knob, and spindle lock interlock. You can easily add the back gear and electrical cabinet interlocks if you wish. You might need to add a relay to power the interlock solenoids, as the vfd may not be able to pass enough power on its own through its auxiliary contacts.
Originally Posted by docwilson
You may wish to keep the original start and stop buttons in concert with the original contactor for the power-up function. Just be sure the contactor is on the input side of the VFD, not the output. On my '67 modular, I'd use the manual safety switch on the front cabinet door to power up the vfd, and would consider using the contactor pushbuttons to simply enable and disable the drive. On the other hand, none of my other vfd-powered machines have that feature, and I get along fine. The VFD might not accept momentary contact switches for the "enable" application, in which case I'd either have to change the switches, or add a small latching relay or programmable relay to provide maintained contacts on the vfd "enable" input.
If you're going to run on single phase, take a look at a Speedstar vfd. They offer a 5-hp single-phase sensorless vector vfd. (I have no horse in that race.) Otherwise, for a 5-hp motor, you'd need a 7.5-hp 3-phase vfd on single-phase, and you'd need to make sure it does not have phase loss detection, or make sure that feature can be disabled. I was looking at a Hitachi unit the other day, and it had phase loss detection that could not be disabled, or at least there was no parameter for that in the manual.
Hitachi units can all be used on single phase input. You size the drive at twice the motor horsepower. A 5 HP motor requires a 10 HP drive.
Originally Posted by rklopp
I was wondering about how much extra it costs to install an encoder type unit and whether or not anyone thinks it would be worth the extra expenditure. As to my input, I was planning on trying to use my 7.5 hp RPC. I remember reading something in another thread that it was important that the RPC have a balanced output. I'm not sure if mine is balanced or not. The voltage measurements across the terminals on the output side are as follows:
L1 and L2 to Gr= 120v
L3 to Gr= 240v
L1 to L2= 240v
L1 and L2 to L3= 266v and 277v respectively
Using single phase input sounds like a simple alternative also. I'm guessing from the above voltage readings that my RPC is not very ballanced.
"L3 to Gr= 240v
"L1 to L2= 240v
"L1 and L2 to L3= 266v and 277v respectively
"I'm guessing from the above voltage readings that my RPC is not very ballanced."
L1-L3 is 10.8 percent high.
L2-L3 is 15.4 percent high.
Assuming those to be unloaded measurements, you've got to get them down to less than 10 percent high. Remove more capacitance from the L2-L3 section than from the L1-L3 section.
Apply the load and remeasure.
Now, you've got to have them less than 10 percent low. Anything above 216 but less than 264 is OK at this point. But, my guess is both will be below 240.
(As the idler becomes larger, the capability to maintain +/- 10 percent, or even +/- 5 percent improves [ * ] ).
"Using single phase input sounds like a simple alternative also."
The Polyspede VFDs, all of which are single-phase input, only, is a very good option if you're not doing too many conversions in the same premises as these are premium-priced drives.
As with the previous poster, I have no horse in the single-phase, only, drive race.
[ * ] The ability of a real utility to maintain the phase-to-phase voltages is a function of its being a true three-phase source, of course, but also because it is an almost infinite source of such power.
A typical 750 MW generation plant has a HP rating in excess of 1,000,000 HP.
Compared to an RPC's 5 or 10 (or whatever) HP behind its manufactured phase, a utility may have 1,000,000 or many more HP behind its B phase.
A large utility may have an average load of 10,000 MW, and that is about 13,333,333 HP.
But, like the three major "systems" within the United States, the "Western System" (which my department within my employer in an earlier professional lifetime designed and operated), the "Texas System" and the "Eastern System" may have several, if not many such 10,000 MW utilities all interconnected together, for service continuity and security reasons.
no wonder Peter is a power electronics expert...
...he used to work for a power utility. Or something related to that.
I did my five-year internship for the California PE exam at this nation's largest municipal electric utility.
However, I did not take the exam, due to a mid-career change to large mainframe computer operating systems, which occupied the entire remainder of my professional career, and which does not require licensing, not withstanding the misguided efforts of certain industry groups to "elevate" their own status, to the obvious exclusion of others, by mandating State licensing of computer software professionals.
If I remember correctly, a while back someone mentioned the use of a isolation transformer to balance the output of a RPC. If this is an option, it sounds like it might be easier way for someone like me to get balanced output. I'm not sure that I'm up to figuring out what capacitors to use and am a little intimidated when it comes to electronics.
The Phase-A-Matic RPC which I use had a similar problem. removed the top box which housed the Caps. and cut one lead on the last cap, taped the ends of the wires and remounted the box. Now voltage is with 5%, just what was needed.
"The New York Power Authority?"
Los Angeles Department of Water & Power (LADWP, AKA DEWAP).
It WAS the largest municipal during the time I was employed by them.
Perhaps not now, but they are undoubtedly the highest in power density, as the service area is strictly limited to the 450 or so square mile area of the City of Los Angeles.
It is no wonder that most of the Department's transmission system is 230,000, 500,000 or 1,000,000 volts.
I don't think a transformer will balance an unbalanced RPC. The vectors between the three legs should still be the same relative size.
My home-built RPC ran at 220V three-phase, and I was afraid of cooking my 208V 10EE, so I picked up a massive three-phase buck-boost transformer and now I have 208V differentially between all three legs. It changed the size of all the differential vectors similarly, and did not affect their relative sizes.
But I think Peter will have the absolute last word on this...