NEMA Inverter-Duty Motor Nameplate Data 1

[dpc]

If a NEMA motor is inverter-duty, does NEMA require this to be stated on the motor nameplate? I'm looking at a photo of a nameplate of 50 hp motor that is supposed to be Inverter Duty, but there is nothing on the nameplate that I can see that would support this.

TIA,

Dave

 

[CJCPE]

NEMA MG1 Condensed PDF can be downloaded at NEMA.org. I believe that will show the motor should have something on the nameplate indicating inverter duty. I can't look at it myself right now.

 

[DickDV]

The terms "inverter duty", "inverter ready", and "inverter rated" are undefined and, as such, are fair game for any marketer or snake oil salesman to use as they see fit.

You will need to read the specs for the motor carefully to be sure you are getting what you think you are getting.

The only truly reliable inverter rating I know of is NEMA and IEEE's MG1 Part31 endorsement. This is real and can be trusted. Basically, this spec is a 1600V pulsed power insulation test along with a higher temp spec for bearing grease. There may be other details in it but that's the most useful part.

Note that MG1 Part31 does not help you as far as choosing the right type of motor for your application.

 

[dpc]

I didn't see anything in the condensed version of MG-1 regarding putting "inverter-duty" on nameplate if motor meets MG-1 Part 31.

I was referring to a motor that meets MG-1 Part 31 requirements. I agree your comments, Dick.

Just trying to determine if it is possible to determine if a motor meets MG-1 Part 31 requirements by looking at the nameplate.

 

[ozmosis]

Found this comment in an internal document from Siemens Inverter Duty Motors:
"NEMA MG1, Parts 30 and 31 outline motor capabilities when used with VFD’s for motors rated 600 volts or less. Part 30 requires that standard motors utilize an insulation system able to endure repeated voltage peaks of up to 1000 volts with rise times of 2 or more microseconds. Part 31 defines an inverter duty motor as having an insulation system able to withstand peaks of 3.1 times rated voltage with rise times of 0.1 or more microsecond."
The Siemens motors stating "inverter duty" would be referring to their specific part number, e.g RGZESDI. So, my feeling is that description of an "inverter duty" motor will refer to the part number on the nameplate rather than any specific reference to NEMA on the nameplate.

 

[dpc]

Thanks all. A re-check with motor manufacturer revealed that previous information given to me was not quite accurate. Motor is not "Inverter Duty" in accordance with NEMA MG1. Motor manuf claims that all their motors have winding insulation in "inverter duty", but it is a standard motor, not Inverter Duty.

I have seen "Inverter Duty" on nameplates, but it doesn't appear to be a NEMA requirement or restriction.

 

[petronila]

Hello DPC,

The Inverter duty windings are different from the standard due to a wide factors:1.The magnet wire is coated with high dielectric strength film and capable to resist the fast rise time pulses.2.Due to the small Wire sizes tend to enhance nonuniform stress distribution they are wuindded with Larger Wire sizes. Example: prefer a 15 AWG than Two Wires 18 AWG .3. Some manufacturers add Phase and ground Protection using stronger dielectric materials or applying sleeving over the first turn at the line end of motor.4. Be sure about the NEMA Design and prefer the A or B than the C or D, because the rotor looses are higher and will heat up more in this NEMA C or D design motors.5. The Insulating material have a higher temperature rating. 6 .The Inverter Duty Motors winding are Treated with resins applied with VPI in order to eliminate the voids.

You could find in some ID motors Insulated bearings and if they are operating at very low speed they will have a Forced air ventilation.

Regards

Petronila

 

[powerjunx]

Dick is right. The term "inverter duty" or the keyword inverter was usually used by OEM sales or application engineer to catch up clients.
I encounter one particular motor distributor, they have plenty of blank nameplates when the customer(unwitty client) ask for inverter duty motor they'll just punch the work on it, though the HP and other rating is indeed real except for "inverter duty" eventually unit is sold. This sounds absurd!

 

[CJCPE]

Here is some additional information that may be of interest:
From: NEMA Application Guide for AC Adjustable Speed Drive Systems

4.2 MOTOR TYPES
4.2.1 General
Performance requirements for various types of induction motors for use on standard sinewave power supplies are identified in NEMA MG1. Some of these types of motors are suitable for use in variable speed applications, dependent on the type of application. Performance requirements are also identified for motors for specific use in variable speed applications….

4.2.6 Definite-Purpose Inverter-Fed
NEMA has recognized the elevated stresses imposed on induction motors by adjustable frequency controls and has developed a performance standard for motors that are specifically identified as “inverter duty” or “inverter rated.” Part 31 of NEMA MG1 addresses issues of particular concern to adjustable frequency control-fed motors such as basis of rating over a speed range, thermal aging of insulation for operation at different loads and speeds, minimum breakaway and breakdown torque requirements, overload and overspeed capabilities, voltage spikes, and vibration, among others. Of unique pertinence to such definite-purpose motors is their ability to better withstand the repetitive voltage spikes that are characteristic of modern, fast switching devices used in adjustable frequency controls….

NEMA Application Guide for AC Adjustable Speed Drive Systems (free download)

 

[petronila]

dpc,

NEMA No require the Inverter duty condition be stated on the motor nameplate, but Some manufacturers like U.S.E.M name plated the Inverter Duty Condition. We was rewind one off this 550 HP-4160 Volts-1200 RPM. In The same name plate have two kind of information divided in two parts, One for Bearings,Frame,Type, HP, RPM, enclosure,phases, max ambient,ID#,INSULCLASS,RPM,SF,HZ,VOLTS and
NEMA EFF,Amps ,PF and Code.

The second part refers to NEMA MG-1 PART 31 and for the 550 HP And is wrotte:
-----------------------------------------------------------
NEMA MG1
PART 31 INVERTER DUTY

TORQUE HZ RANGE MAX RPM AMPS
2430 LB-FT 6-60 120-1200 73.5

1.0 SF OVER TEMP PROT 2.

Made in USA U.S ELECTRICAL MOTORS
-----------------------------------------------------------

I have seen this Too in Marathon and Baldor name plate Inverter Duty motors.

Regards

Petronila

 

[DickDV]

You only got all that nice information because the motor was large, in fact, larger than any NEMA frame. NEMA quits at 449T which gets you a 300hp motor max.

On smaller motors, you will often see motors described as "Inverter Duty" or "Inverter Rated" or Inverter Ready" without any mention or compliance with MG1 P31. I've even seen some manufacturers put Inverter Ready on all their three phase Insulation Class F motors.

As I said earlier, you have to know what you are buying if it doesn't say MG1 P31.

 

[place1234]

NEMA does not specify all these detail information to be put on the nameplate for inverter duty.
DickDV is right, it's all manufacturer's interest to put detail info on the nameplate, normally medium and large size motors. Some manufacturers like "Reliance Motor", they put constant torque, power, very detailed on the nameplate.

 

[petronila]

Some small motors have too Inverter duty name plate.

NEMA No require the Inverter duty condition be stated on the motor nameplate

For it, is not mandatorie state on name plate the inverter duty features.

If some manufacturers like U.S.E.M, Baldor, Reliance and Marathon are labelling the Inverter Duty name plate with THE SPEED RANGE, TORQUE, FRECUENCY RANGE and Current data, they are giving to the end user a very usefull information and a guarantee about the INVERTER DUTY RATING.
This practice is not exclusive for large machines and cover too samll one.
I think, With the increase use of VFD in a very close future, all motors manufacturers are going to state on name plate the Inverter duty features and Maybe in further NEMA Disscusions the INVERTER DUTY or INVERTER RATED name plate will be stated mandatorie.

Regards

Petronila