PM-949V - need 3 HP motor specs

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mikey553

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I am setting up the VFD to drive the 3 phase motor on my mill. For that I need to know the motor full load amps (FLA). Unfortunately my motor nameplate is not stamped correctly. It shows 6.2A for 220V. 3 HP motor should have higher FLA. Matt assured me that I have a 3 HP motor, just the nameplate is misstamped. Variable speed heads for 949 mills always come with 3 HP motors. Amps data stamped apparently came from a higher voltage motor.

Anybody has a similar 3 HP motor? Would you mind telling me what your FLA is for 220V supply? Your help will be greatly appreciated.

By the way, this motor is of open design. It sucks the air from above the motor, routes it around motor coils and blows it out of belt housing vents. This may explain how they could build such a light weight but powerful motor. It weighs only 52.6 lb complete with pulleys. Need to remember to put some fine mesh wire cloth over the motor top to protect the motor.
Since I took the mill apart for moving I weighted all major components. If anybody needs the weight data, let me know.

DSCN1802.JPG


DSCN1800.JPG
 
I would set the VFD up according to the motor nameplate and allow a 150% overload setting which is fairly typical. Many VFDs you set the kW setting and not the amps. Below is a newer 949 motor which species 8 amps for 3 Hp, but it is a constant Hp dual speed motor. You rarely use anything near the full Hp rating of a mill motor in a hobbyist setting, so using the 6.2A with the higher overload should work OK and not but your motor at risk. I doubt that the nameplate is wrong, but even if the motor was 100% efficient, 3Hp works out to something like 7 amps. Often, it seems like Asian motors are a bit optimistic as to Hp relative to the motor frame size.

Motor Name Plate.JPG
 
Amps * volts = watts

Watts / Volts = Amps

750 watts apx is 1 HP. Most guys figure 800 watts per real horsepower with various losses due to heat parasitic load etc.

3 X 800 = 2400 Watts (PEAK AT ON A FULLY LOADED MOTOR)

2400/220=10.91 amps

However, you likely have between 230 and 240 actual voltage. So instead figure
2400/240=10.0 amps

****** ALERT KEEP READING ******

All of that would be well and good if we were talking about a single phase motor, but we are not. We are talking about a 3 phase motor, and you have amps per phase. The amps per phase for a 3 phase motor of the same size will be much less than the amps per phase for the same size single phase motor. Look at the table on this page: https://www.engineeringtoolbox.com/ampere-phase-d_449.html

Scrolls down to where it shows a 10.4 amp load on single phase 240, and then look over to the 3 phase amps per phase rating on the same line.

6.1 amps. Amazing. Very close to what your motor plate says. Add in the factors I mentioned and you are probably dead on.
 
[QUOTE="Anybody has a similar 3 HP motor? Would you mind telling me what your FLA is for 220V supply? Your help will be greatly appreciated.

By the way, this motor is of open design. It sucks the air from above the motor, routes it around motor coils and blows it out of belt housing vents. This may explain how they could build such a light weight but powerful motor. It weighs only 52.6 lb complete with pulleys. Need to remember to put some fine mesh wire cloth over the motor top to protect the motor.
Since I took the mill apart for moving I weighted all major components. If anybody needs the weight data, let me know.[/QUOTE]


Here's the plate from my 935, also 3hp:

https://flic.kr/p/SYJ8PC

Based upon a printout of my VFD parameter decisions, I set the FLA to 8.5A during VFD setup.

This shows the casing for my 3hp motor... it does look different:

https://flic.kr/p/21yvvpu

I forget the name of that casing style but there is one. I also recall I was able to track down the motor manufacturer's web site to seek out additional info on winding insulation but I do not seem to be able to put my hands on that link... I probably no longer have it but it would be, IMO, worthwhile to take a look. Good luck.
 
A typical brand name 3 HP 3 phase motor has FLA of 7.8-8.8A. This came from the actual industrial motors I have seen. This is not from a book, web site or from my imagination. 3 HP on American nameplate means the mechanical power on the motor shaft end, available to the user. It is not the VA power motor pulls from the grid.

I agree the Chinese motor manufacturers are a bit optimistic about many things, horsepower included. Mksj, I can barely see from your picture, but it looks like your motor is 2 poles, 3 HP and weighs 30 kg. My nameplate shows 4 poles, 3 HP and 24 kg. Being 4 poles my motor should be bigger than yours with the same horsepower.
Anybody has a motor similar to mine?
 
Thank you Clock work for your reply. 8.5 A is right on the money for 3 HP motor. Your motor is most likely of TEFC (totally enclosed fan cooled) design. Still the question stands - do I have a 3 HP motor or not? Also what is the correct FLA for my motor?
 
Actually I've often found cheaper Chinese motors are rated at stall.
 
The motor shown is for a PM 949 (pictures from are from the owner of the mill) it is both a 2 and 4 pole motor rated at constant Hp on either winding. It lists 8.5A on 2 pole and 8.0 on 4 pole, the nameplate states a motor weight of 30Kg. It is a TENV, so fairly substantial. I also have a Taiwanese 3Hp VFD motor on my knee mill which is a TEBC, the nameplate is 8.0A at 220V. As I stated, I would set the VFD to the motor nameplate amperage and dial up the overload, I seriously doubt that the nameplate would be in error, but whatever. Please also note that some motors may be rated at 2Hp for continuous duty and 3Hp for shorter time frames, which may be the case here.
 
Horsepower or FLA is all about how efficiently you can cool the motor. My motor being of open frame type can be cooled better than an enclosed frame motor. The cooling air can directly flow over the coils. This could be why this light motor can still develop 3 HP and not overheat. After all Matt guaranteed the motor is 3 HP. I even remember the email from the manufacturer sent to me by Matt, where they said the nameplate was misstamped.

If you ever heard about hermetic refrigeration motors, it is amazing how much power can they pack in a small frame. For example a 200 HP hermetic motor would weigh about 150 lb - way less than a regular motor of such power. This is because such motors are refrigerant cooled, which is a very effective way of removing the heat.
 
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