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Hitachi SJ-P1 VFD: Overcurrent at low frequencies. Fine at higher

R

rbmgf7

Aluminum
Joined
Oct 18, 2017
I'm about to tie up this Tree retrofit but have been having a heck of a time with the VFD. I'm still relatively noobish with VFDs but I've set up small, simpler ones without issue.

In the meantime, I've disconnected the spindle belt to just run the motor. I have the limits from 10 to 140Hz. Anything above 70Hz runs fine; pulls about 11amps once running and runs smooth. But when I go below 70Hz, it surges/hunts then throws and overcurrent alarm. Pulls around 50amps before it trips.

Can't seem to find anything nor figure anything out.
 
johansen said:
Read the manual amd go through each configuration in the vfd and set them accordingly.
Click to expand...

Figure that would've been implied.

I've done both. Configured the VFD to the motor specs as well as let the VFD auto tune.
 
What did you set up for "motor rated speed" and "motor rated voltage"?

It kinda sounds like there is something funky there, as if the V/Hz is getting too far out of whack.
 
JST said:
What did you set up for "motor rated speed" and "motor rated voltage"?

It kinda sounds like there is something funky there, as if the V/Hz is getting too far out of whack.
Click to expand...

200V
Speed is rated for 8k but I'm running it at 6k (being a wimp).

Rest of the info: 3p, 4p, 2.2kw cont (3.7 peak for 15m), 11A cont (15 peak).

I've reset the drive with no change. I've followed the troubleshooting suggestions to correct the problem but no change.

It's the original Fanuc motor that came in the Journeyman 325s. Might have a way to test the motor (I think we have a megger at work I can borrow).
 
I had a very similar problem a while back with a 5 HP motor. It was occasionally having trouble starting and always pulling way more amps than it should've been at low frequency settings. Very jerky at lower frequencies. My drive is not SLV so a few tweaks to the V/Hz curve at the low end solved my problem. If your drive is SLV I'm sure you've already run auto-tune, which should correct any of those issues... So maybe yours is something else. Good idea to check out the motor completely.
 
You should post the name plate of the motor and the Hitachi P1 model you are using and if you are using it on single phase input or 3 phase or RPC. The Hitachi P1 series require significant derating for single phase input and also under ND mode with an overload of 150% for 1 minute. So the minimum P1 model would probably be the P1-00228-LFUF (17.5A in ND), the next model down is rated at 11.0A which may be marginal or inadequate for the motor.

Hitachi P1 manual seems a bit worse then the previous ones, so I would check some of the motor parameters and adjustment parameters. I am assuming that the base speed of the motor is 50 Hz (1500 RPM), I would run it in Sensorless Vector mode, and any changes to the motor parameters or resetting the VFD cancels the auto-tuning so I always run that last. The WJ200 required you to select the auto-tune data for the motor, but the P1 seems to automatically load it. As far as the motor rating and load, I am not aware of how to adjust the VFD for a 15 minute overload at 3.7kW

IM: Induction motor
General
motor items
Motor Capacity[ Hb102] (kW) = 2.2
Motor Number of motor poles[Hb103] = 4
Motor Base Frequency[Hb104] = 50
Motor Maximum Frequency [Hb105] = 200Hz would be 6000 RPM
Motor Base Voltage [Hb106] = 200V
Current[Hb108] = 11A

Control mode [AA121] 08 Sensorless Vector control otherwise try 00 V/f control constant torque or may require torque boost and tweaking in V/f mode

Stability Constant [HA110] To adjust the control for reducing the hunting of motors
Output voltage gain [Hb180] Decrease it if the motor is hunting. A lower setting decreases the output voltage.

Auto tunning
Revolving tuning [HA-01]=02

See page 12-9-11
Unsteady revolutions at low speeds: The control system has a speed response that is too low. Make an adjustment by incrementing the response adjustment [HA115] by 5% each time.

Running Sensorless Vector mode [AA121} = 08
Speed response adjust [HA115] range 0-1000% to increase responsiveness by increasing %
 
rbmgf7 said:
.....................
It's the original Fanuc motor that came in the Journeyman 325s. Might have a way to test the motor (I think we have a megger at work I can borrow).
Click to expand...

I am not familiar with that unit. However, some spindle motors are peculiar, made in some cases to take what appear to be considerable overloads. The way that is done is to design the motor as a low voltage high current motor, good for more than the actual power in terms of current capability at rated conditions. It is somewhat like using a 5 HP motor for a 2 HP load, with the plan of maintaining power at 2 HP down in the range where the motor would have lost power (power being proportional to torque x rpm, and so dropping at low speed unless current, which is torque, increases).

It still does lose power vs 5 HP, but it stays above 2 HP to a lower frequency/rpm. But it does so by drawing more current. Since it is a 5 HP motor, it can draw 5 HP worth of current while producing 2 HP at lower speeds (and lower voltages).

The special designs are made to accept the high current. The high end is normally not an issue, since a 50 Hz 120V motor is a 100 Hz 240V motor, and a 200Hz 480V motor, and those motors are made to spin fast.

If you are using that type of motor, it may have "nominal specs" that are for the usage, and not necessarily for its capability, and will only work well with a matching drive. Because your motor is good to 8k rpm, I suspect that type is what it is.

If it is indeed a "special" motor, you may need a different, higher current VFD.

You might try the VFD with a known standard motor of the rated power/current, and see if it operates OK. I'm betting it will.

You still may be able to use it, but you will need to have solid knowledge of the real motor specs to make sure.
 
mksj said:
You should post the name plate of the motor and the Hitachi P1 model you are using and if you are using it on single phase input or 3 phase or RPC. The Hitachi P1 series require significant derating for single phase input and also under ND mode with an overload of 150% for 1 minute. So the minimum P1 model would probably be the P1-00228-LFUF (17.5A in ND), the next model down is rated at 11.0A which may be marginal or inadequate for the motor.

Hitachi P1 manual seems a bit worse then the previous ones, so I would check some of the motor parameters and adjustment parameters. I am assuming that the base speed of the motor is 50 Hz (1500 RPM), I would run it in Sensorless Vector mode, and any changes to the motor parameters or resetting the VFD cancels the auto-tuning so I always run that last. The WJ200 required you to select the auto-tune data for the motor, but the P1 seems to automatically load it. As far as the motor rating and load, I am not aware of how to adjust the VFD for a 15 minute overload at 3.7kW

IM: Induction motor
General
motor items
Motor Capacity[ Hb102] (kW) = 2.2
Motor Number of motor poles[Hb103] = 4
Motor Base Frequency[Hb104] = 50
Motor Maximum Frequency [Hb105] = 200Hz would be 6000 RPM
Motor Base Voltage [Hb106] = 200V
Current[Hb108] = 11A

Control mode [AA121] 08 Sensorless Vector control otherwise try 00 V/f control constant torque or may require torque boost and tweaking in V/f mode

Stability Constant [HA110] To adjust the control for reducing the hunting of motors
Output voltage gain [Hb180] Decrease it if the motor is hunting. A lower setting decreases the output voltage.

Auto tunning
Revolving tuning [HA-01]=02

See page 12-9-11
Unsteady revolutions at low speeds: The control system has a speed response that is too low. Make an adjustment by incrementing the response adjustment [HA115] by 5% each time.

Running Sensorless Vector mode [AA121} = 08
Speed response adjust [HA115] range 0-1000% to increase responsiveness by increasing %
Click to expand...

Drive model is P1-00460-LFUF. Here's the link from where I purchased: VFD P1-00460-LFUF, AC Motor Drive

Can't get a clear pic of the motor plate since it's inside the frame and plate is against a wall. Here's what I have:

General Numeric (by Fanuc) A06B-1002-B600 #2000. There's no other pertinent information on the plate that is required by the VFD

I haven't messed around too much with the other settings besides accel and decel times but it doesn't make a difference. I'm having troubles getting the motor to stop on it's own. I don't have a RB hooked up yet (I have the one that came with the mill) so I'm trying to use the VFD to brake over a long period of time but always get OC alarms after a couple seconds.

I'll adjust some of the settings you recommend as well as what JST is recommending. I wish I had a spare motor as I'm sure the VFD is fine too.
 
I had this same issue with a installing a vfd to replace and old one on a variable speed clausing.

One parameter that made the difference was the base hz setting. I mistakenly thought the parameter wanted to know the input hz, when in reality it wanted to know what the motor was rated for. Initial setting was 60hz and the motor acted just like you described, almost to the T. After many hours of frustration, I realized the issue and changed to the motor nameplate rating which was 200hz.

The lathe was ready to run after that.
 
MotoX said:
I had this same issue with a installing a vfd to replace and old one on a variable speed clausing.

One parameter that made the difference was the base hz setting. I mistakenly thought the parameter wanted to know the input hz, when in reality it wanted to know what the motor was rated for. Initial setting was 60hz and the motor acted just like you described, almost to the T. After many hours of frustration, I realized the issue and changed to the motor nameplate rating which was 200hz.

The lathe was ready to run after that.
Click to expand...


This is what I was asking about.

The problem you have is basically that you have "a motor", and none of the basic information on what it is rated at. At least if I understand correctly, you have a motor with zero nameplate info. A special purpose motor for which you have no specifications.

Similar sort of problem as machining mystery metal, only it's a motor. I won't say it cannot be done, but it may take "inspired guesswork".

If this motor is what you have to use, the place to start is to determine what you KNOW about that motor, or can find out.

It may be a lot easier and more productive to obtain a motor that you can get specs for, preferably one that has a normal nameplate.

Looking on-line, I see that these motors are apparently quite expensive. I could find zero for specs. You can maybe sell that one and get another more suitable motor, while coming out ahead.

And, given that it is clearly a special purpose motor, that may be your best approach to the problem.

a06b-1002-b600 - Google Search
 
You can figure out the volts per hz saturation curve by running the motor at some nominal rpm amd varying the voltage, by programming in a different base voltage or frequency into thr vfd.

I do not believe the motor is a 200v 50hz motor.

Try 200v 100hz amd try again.
 
I figure if I can't get the settings just right, I can default to replacing the motor.

Spotted this one from the Amazon (sorry, image is fuzzy). Seem like a suitable replacement? Claims it can also be inverter duty. Figure I need to wire an independent fan for cooling at slower speeds. Another issue is I'm running a reduction on the current setup so I'll have to essentially "flip" the pulleys to keep my spindle speeds. I loosely say flip but I'll have to install a larger pulley on the motor due to physical constraints (Z axis motor assembly is sandwiched in between the motor and spindle. Funky design). I figure I'll at least need a 3:5 ratio if I want a 6000 max spindle?

Annotation 2021-04-20 131407.jpg
 
johansen said:
You can figure out the volts per hz saturation curve by running the motor at some nominal rpm amd varying the voltage, by programming in a different base voltage or frequency into thr vfd.

I do not believe the motor is a 200v 50hz motor.

Try 200v 100hz amd try again.
Click to expand...

Wait wait wait. We have something. Hot diggity. Works great and doesn't OC. It also stops too. Woo Hoo.

Thank you much!
 
OK I just started watching and the Hot diggity attracted my attention what happened? I have the same motor in my Tree and am about to install an encoder on it because I have no low end torque. I have never found any info for the wires, other than power. Does the motor have an encoder? For some reason I thought it did...long ago, but never got any wiring data or colors...nothin' I'm using a Unidrive sp 2203 for the VFD so it's possible I have some parameter(s) incorrect.
Please don't stop the thread now...9-)
 
I have no idea what you are saying.

Yes you have to go through all the parameters and figure them out. For example dc injection braking and the ac regeration parameters have to be set right to get good hand off between the two in order to stop the spindle as quickly as possible.

The boost volts have to be set right to get the most low end torque without overcurrent or overheating the motor.

Running the motor unloaded with a wattmeter on the line side of the spindle drive will help you figure out if the motor is saturated. My 5hp 76 pound inverter rated 1750rpm motor only draws 200watts at 200v60hz but it draws 300 watts at 240v 60hz no load loses
 
lavrgs said:
OK I just started watching and the Hot diggity attracted my attention what happened? I have the same motor in my Tree and am about to install an encoder on it because I have no low end torque. I have never found any info for the wires, other than power. Does the motor have an encoder? For some reason I thought it did...long ago, but never got any wiring data or colors...nothin' I'm using a Unidrive sp 2203 for the VFD so it's possible I have some parameter(s) incorrect.
Please don't stop the thread now...9-)
Click to expand...

Mine has an encoder built in. Haven't looked at it yet.

There are wiring manuals around on the internet. Here's a link: Dynomotion/Kflop/Kanalog > Tree325 Retrofit Started - Page 11

Has the wiring for the pulse encoder to the Yaskawa VFD.

I'm not saying my VFD troubleshooting is resolved but it's a step in the right direction.
 
Thats probably way to low an RPM (350) for that motor and drive. That's a ten to one drop from rated speed. That effectively means 10 times the current for the same torque and that's only if it's a vfd rated motor (doubtful). If it's a variable speed drive you're better off using that. Also, be carefull about how much you over-speed the motor the motor. 1) it may not be balanced well enough for that, 2) if you don't have a braking resistor it's going to over-voltage the drive (regenerative feedback) every time you drop the speed (including telling it to stop)
 
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