Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in

Motor/VFD Question 2

Status
Not open for further replies.
MagneticFlux

MagneticFlux

Electrical
Mar 30, 2004
32
0
0
US
Greetings all,

I would like some opinions/suggestions on an issue being experienced with a VFD and motor.

Motor Specs:
Volts 460
F.L. Amps 239
S. F Amps 275
RPM 1200
Hertz 60
HP 200
Duty CONTINUOUS
TYPE TD
Frame 447T
Serv. F. 1.15
Phase 3
Design B
Code G
Insul Class F
Eff 100% 96.2
Connection 6 Lead Star-Delta
Link
Drive Specs:
Product: Allen Bradley 23C-D460A103NNMANN
Description: PowerFlex 400, Fan & Pump Packaged Drive

Version Voltage Code 480 VAC, 3 PH
Output Current 460 Amps
Human Interface Module Fixed Keypad
Enclosure IP20 / Type 1
Version RS485
Frame Size H

Setup:
Motor is driving a P type fan via direct coupling
Motor connection = DELTA (connection has been verified twice)
Drive tuned and configured for 200HP motor, all settings default with exception to motor nameplate data, voltage input and auto-tune data.
Motor Data = (matches above info)
Voltage Input = 480 Volt
Auto-tune = calculated by VFD based on above info
Motor Control Mode = V/Hz
Application Mode = None, no PID inputs, being controlled via HMI

ISSUE: (Note that I am not performing the install/setup, I got involved because someone asked me to look into this).

The motor will not come up to full speed before O/C limit is reached. With frequency set-point at 60Hz: as the motor ramps up to speed (ramp time = 30 seconds), at +18HZ an over current alarm is indicated on HMI. Longer ramp times have no effect. The VFD will ramp up to ~18Hz and go into 'current trim mode' as this is highest frequency achievable before current output peaks at ~275 amps(SF amps). Adjusting the frequency beyond 18 Hz triggers O/C alarm.

Motor manufacturer recommends leaving the motor connected in delta and starting ATL to determine if this is a drive or motor issue. This was thought I had as well but Size 5 starters are not laying around like they used to be 20 years ago so, for the time being, that option is off the table. My thoughts are centered on drive parameter settings but the settings are as basic as they need to be for nominal operation. Any thoughts?
 
Replies continue below

Recommended for you

Sort by date Sort by votes
Doesn't look like you did anything wrong. It's a single voltage motor according to that drawing (assuming that's the correct drawing for that motor), so delta is the only connection choice you have.

Did you megger the motor and leads? Note that you must disconnect the leads from the VFD first.

What's the distance from drive to motor? Could (remote possibility) be cable capacitance charging current is exceeding the capacity of the transistors.

If anything were wrong with the drive itself, you would be getting a Fault immediately. It will not Current Limit into a bad transistor.


" We are all here on earth to help others; what on earth the others are here for I don't know.
" -- W. H. Auden
 
Upvote 0 Downvote
Thanks all for responding, all good advice.

Answers / clarifications to your responses:

@jraef: Connection diagram is correct. Yes, motor was not only checked but replaced (had new spare on hand). Distance between drive and motor = ~250', line and load reactors installed within 6' of the drive. VFD was replaced (with new one) after new motor was installed and did not remedy the problem.

@iop95: I am looking into this. The V/Hz curve for a default Fan/Pump setup (current configuration, none adjustable parameters) is drastically different from the "default custom" (adjustable via parameters) curve. You may be on to something.

@waross: Do you mean a flipped coil or external connect? Motor(s) are new, not rewound. External connections have been confirmed to match nameplate and attached connection diagram.

@edison123: If the motor, while connected STAR, was to run at base speed drawing nominal current, what would that suggest as the problem?
 
Upvote 0 Downvote
Well I once saw a motor with a bad bearing on the brake. The race had failed and the bearing balls bunched up and jammed the shaft.
You could see the problem by looking at the bearing closely.
The millwrights went around in circles for hours trying to release the brake. Direct current to the control solenoid, remove the solenoid and put air pressure directly to the brake.
For hours, the answer to the suggestion that the bearing had failed was:
"There can't be anything wrong with the bearing. It's brand new."
I would connect a 12 Volt battery to T1 and T2 and go around the end coils with a compass.
Then connect the battery to T2 and T3 and repeat.
Then connect the battery to T3 and T1 and repeat.
You should see a repeating pattern of magnetic polarity.
But then why waste the time? It's brand new.
Another option is to disconnect the fan and run the motor unloaded. See if it comes up to speed with balanced fairly low currents.
The fan may have a mechanical problem or it may be intended for a belt drive.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
Upvote 0 Downvote
About a year ago, I was called by a ship building company that had two brand new motors that were tripping on overcurrent during starting. I found the delta leads were not properly connected. Instead of A1B2, B1C2 and C1A2, both motors had A1A2, B1C2 and C1B2. A proper re-connection on-board solved the problem in 15 minutes. The shipbuilder was fuming over the german OEM's mistake. Something for you to think about.

If you connect in wye (for test purposes), then better to decouple the load since the torque is not going to be great.

Muthu
 
Upvote 0 Downvote
@waross: Bro, I would NEVER consider someones advice as a waste of time while trying to resolve a problem [bigears]. Regardless of the motors condition (new vs rewound), I have all ready suggested that it be uncoupled and ran. That was done, results; motor ran up to base speed, current about 25% of name plate (or at least that whats I am being told). In regard to the power transmission, I agree with your thinking that it may be undersized for direct coupling. There are setups currently on-site that are utilizing 200HP motors to drive fans that are half the size AND at higher speeds (1800RPM motor driving fan at ~2000RPM). I mentioned this while on-site and got the 'deer in the head lights' stare. I then recommend that the fan manufacturer review and verify the HP requirements; no feed back yet. If I provide specs on the fan, could you approximate the needed HP?

@edison123: The motor will run on DELTA when uncoupled from the load. We considered running it on STAR while coupled to load but our concerns then focused on HP/Torque. This being a fan (load increasing with RPM) I don't think it would come up to speed.

I am going to suggest that the low end torque parameters be adjusted per iop95's post. If that fails, I will follow up with reconnecting the motor in STAR and attempt to run under load. I will advise on the results.
 
Upvote 0 Downvote
If you can run it up to speed, unloaded, in delta, make sure that the currents are well balanced.
I suggest that you post what information you can about the fan here.
Manufacturer and model number may allow us to locate specs for the fan.
I would also suggest posting in the "HVAC/R engineering" forum under a heading such as "I need help checking fan sizing."
Them instead of posting the info, post a request that the fan gurus look in on this forum. I believe that you can post a link to this thread.
Sorry about the attitude, it was uncalled for.
My rancor was not directed at you, but at those who will not follow trouble shooting steps because of an assumption.
Not always but too many times, the assumption has turned out to be false.


Bill
--------------------
"Why not the best?"
Jimmy Carter
 
Upvote 0 Downvote
First, set the VFD panel to display current or load.

Manually start the motor with the VFD and then MANUALLY, slowly, over a minute or two speed up the motor with the VFD panel. If the fan is too big you'll see it probably loading-up or rather overloading somewhere before running speed. Because the fan load goes up non-linearly it will be easy to see the problem if it's fan/load.

Keith Cress
kcress -
 
Upvote 0 Downvote
Another assumption that we are all making is that the voltage is correct. Has anyone verified that the VFD is getting a solid 480 Volts?

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
Upvote 0 Downvote
Something that occurred to me was what you meant by "P type fan", so I googled it. Is this a variable pitch vaneaxial fan then? If so, are you starting it with the vanes turned in to where there is no flow, or turned all the way out for maximum flow? If turned out, the motor may be unable to accelerate it, because in that type of fan the load may be excessive from the outset. You may need to accelerate it with the vanes closed until you have overcome the inertia of the fan itself, then open the vanes up and trim the speed after it is running.


" We are all here on earth to help others; what on earth the others are here for I don't know.
" -- W. H. Auden
 
Upvote 0 Downvote
I have some time scheduled this weekend to visit the site and attempt to resolve this problem.

@waross: I will monitor the phase currents and advise. I have asked multiple times for the fan manufacture name and model; no response. I will try and locate this information myself this weekend. The incoming voltage to the drive is steady and constant @ 480VAC both loaded and unloaded.

@itsmoked: I suggested this as well but was unable to make a determination at the time. I believe we will see noticeable results after changing the torque curve.

@jraef: 'P Type Fan' = Centrifugal fan type P-wheel - Straight backward blades. High efficiency, self cleaning, changing in pressure have little influence on air volume. Ref.
@iop95: The VFD is configured operate in 'Fan/Pump Mode'. Having read your comments, I believe we should see some improvement in changing this to 'Custom V/Hz' with a value of 9 or 10 set for P60. I am posting a link to the manual(s) if anyone would like to review the default settings and make any suggestions.
Ref manual: Prog manual:
The limited information on the fan that I have so far is:
1) Fan wheel diameter = ~96", weight = 1,200 lbs
2) I hope to have more for you all on Monday

Note: This fan is part of a baghouse ( ) type filtering system, the system is new. The manufacturer has been unable to get this fan up to speed.
 
Upvote 0 Downvote
P60, P61 and P62 must be set in voltage not V/Hz ratio.
I suggest to try these settings: P63=25Hz, P60=25V, P61=10V and P62=210V
I can't find a function to mask current alarm for few seconds (or at stat-up) to avoid current limit alarm.

This motor have nominal torque about 1200Nm; if supose fan load at nominal speed is 90% of motor torque, mean about 1100Nm; I think is correct to supose fan torque as Mf ~ k(speed)^2, so at 18Hz, fan need about 100Nm torque only.
If motor trip: or inertial load is too much (reduce accelerating time) or sometingh is wrong in V/Hz relation; may you check output voltage when motor trip?
With high aproxiamtion, J fan is about 200kgm^2, so need to keep acclerating time (0 - 60Hz, if is a single ramp) above 30 seconds.
 
Upvote 0 Downvote
FAN DATA:
20170917_073300_hag8fv.jpg


Fan Diameter: 72 inches
Fan Width: 19 inches
P Type, Forward Pitch

Measurements are the actual fan

MOTOR DATA:
20170917_095053_e0ag8p.jpg



DRIVE DATA:
20170917_094938_bssz34.jpg
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Sujj33
  • Locked
  • Question
VFD, Motor, Vibration
Replies
3
Views
18
electricpete
electricpete
MitchusMaximus
  • Locked
  • Question
General VFD Enclosure Cooling Question
Replies
19
Views
20
Heaviside1925
Heaviside1925
Pratik jain
  • Locked
  • Question
Replacing DC motor with induction motor & vfd
Replies
5
Views
16
Gr8blu
Gr8blu
fab1961
  • Locked
  • Question
VFD driving a two-phase motor 1
Replies
8
Views
11
jraef
jraef
edison123
  • Locked
  • Question
Suitable VFD for MV wound rotor motors 3
Replies
12
Views
24
PersonalProfile
PersonalProfile
Back
Top