1725 at 50%

bbseay

Member
Join Date
May 2003
Location
OK.
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54
would it be bad to use a 1725 motor with vfd at 50% indefinitely?

would the life of the motor be shortened?
 
bbseay said:
would it be bad to use a 1725 motor with vfd at 50% indefinitely?

would the life of the motor be shortened?

In a nut shell yes.. Unless you buy an inverter duty motor with auxiallry cooling..Even still why run it at 50%...use a gear box and then the vfd to "fine tune"
 
The quick answer is probably not. But, as in all things, the true answer is 'it depends'. Is it a TEFC motor? Running at 50% speed means a lot less air is drawn over the motor because the fan speed is slower. If the motor is lightly loaded, that may not be much of a factor. If it's operating at close to full load all the time, it's going to run hotter and that's going to shorten its life.

On the other hand, if knowing that it's likely to run hotter means that you do a better job of keeping it clean, you might even get a longer service life out of it.

Running a motor with a VFD gives you the ability to control the acceleration rate. That saves a lot of wear and tear on the drive components compared to across-the-line starting.
 
If the motor is 100hp or smaller, you can run it at half speed fully loaded without concern for overheating--this according to most manufacturer's published data for ODP and TEFC motors.

In fact, under 10hp, you can go as low as one-quarter base speed without concern.

This isn't my data now, it's the manufacturers!
 
DickDV said:
If the motor is 100hp or smaller, you can run it at half speed fully loaded without concern for overheating--this according to most manufacturer's published data for ODP and TEFC motors.

In fact, under 10hp, you can go as low as one-quarter base speed without concern.

This isn't my data now, it's the manufacturers!

Damn you learn something new every day!!!

Thanks

D
 
VFDs

We generally use VFDs for applications where motor speed is changing on a regular basis. We may install a VFD to find what speed a certain conveyor should run at or a chain conveyor may need more or less speed due to design changes in the mill. After everyone is happy with the new speed, we calculate the new chiv size based on the motor RPM at 60hz and reducer ratio to get the new RPM needed to get the desired speed. VFDs are expensive. If you use a standard motor on a VFD at 50% the rotor IR losses are high and a lot of heat is generated. We found the motors to be OK but the bearings were usually cooked resulting in complete and total mechanical failure. The high efficiency motors (very expensive) have better material, (less impurities ) and far less IR losses in the rotor, resulting in a lot less heat. They have no problem.
Bruce:)
 
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