motor to be run at higher frequency than it is designed for.

Provided the motor rating parameters are entered into the VFD correctly then there shouldn't be an immediate problem, as the VFD's on-board control algorithms will look after the motor.

What may be found is that with a fan or blower, because the load varies with the rotation speed raised to a higher-than-unity power, the load current at 58Hz may rise beyond the rated full-load-current of the motor. The VFD should take care of it if correctly programmed either by reducing the motor speed to bring the motor within rated operating limits or by tripping out, in which case a larger motor might be the only solution avaliable to achieve the CFM required; check the cabling size and VFD rating to make sure they are compatible. Of course, if the motor is conservatively rated with respect to the fan size, then this issue might not occur. It can't be seen from here, so it's experimentation time with the installed equipment. It is worth a phone call to the fan supplier's technical help-desk to check the fan/motor combination and its capability at the higher frequency.

I agree, should be fine as long as the motor is capable of the expected overload. But you also have to realize, once you take a motor over its design frequency, you have run out of voltage to maintain the proper Volts/Hz ratio necessary to continue to create torque. So above 50Hz, you are in what is called "constant power mode" meaning your motor power remains the same and torque is dropping off with increased speed. As PWSlack said, the load in a fan will increase with speed so you get more load with less torque and that results in a rapid increase in overload risk. That overload condition increases at a logarihmic rate as speed over unity is increased, right up to the point where eventually, the motor no longer produces enough torque to spin its own mass. So just be careful and watch everything.

<advisable to run this motor at 58 hz>

You know your job is best done at 58Hz.

You know it works.

You are worried?

Watch the Amps aand feel the Temp when the Work is going on.

Theoretically 58 HZ will be OK for the Motor's Electro-magnetics.

Bearings/winding mechanics always have large margins.

Wow, hold your horses ,

Assuming that this is not a home made unit, but rather a well designed factory made one, where the manufacture specifies a certain CFM at 1500RPM/50Hz. and if the rated RPM is not obtained under these conditions, but at a higher speed (58Hz), that means that the culprit is the blower, more specifically the blade pitch and not the motor or other circuit component... Moreover, If the rated CFM are met at the 58HZ, there is NO additional load on the motor, and the only extra loss will be motor internal heating due to asynchronous conditions. This should definitely be taken into account. If there are no power reserves at the power supply or the motor, than de rating of the CFM should be considered.

That doesn't mean that I disagree with you that nothing Will go wrong for the moment, It may, or may not. But just to focus on what I believe the real problem is.

BTW, what does MUKULMAHANT means? (curiosity killed the cat...)

Wangito.

Thanks Wangito.

• First things first:Mukul C Mahant is my complete name.
• Mukul is Old Sanskrit for a flower Bud just going to bloom !
• Mahant is a Hindu familyTitle meaning Pious Teacher to society's lower strata-and who looks after their spiritual wellbeing-carries on in the family whether you are that or not.
• Don't blame me-this SURNAMEwas given by somebody 500 years back.

And now the Second part:

WANGITO?

Impressive. And I always thought the old testimony is the leader in saying a lot with just few words. I guess I was wrong...

Wangito is the name of the guy in my avatar. (also Sanskrit if I am not wrong?) who, to my greatest sorrow passed away on August 31st this year, (that is 2 weeks ago) at 12 years of age. The MOST beautiful Chow-Chow ever lived.

Wangito. (Ira G. Curtis...)

thanks for ur replies

The motor with V/F can be run at speed In the ratio of 1:10 below synchronous speed.When u run it above syn speed Ie more than 1500RPM to keep V/fcosntant U may have ti raise the voltage. The other problem if Voltage is not raised is lower Torque.More than electrical Mechanical problems may arise like Earlier Failure of bearings,noise etc.If possible try using a 3000rpm (2P) motor and operating it at lower speed .This will also give you a wide speed range ,choice of Higher speed if required comfortably without problems.

The motor manufacturer needs to say that running at the increased speed will not damage the motor.

Hi, check and see if your fan is turning the proper rotation. I have seen many squirrel type fans installed with the rotation indicator pointing the wrong way. The fan will push some air but not as good as the proper rotation almost 45 to 50% less. A 50 Hz motor should rotate at rated rpm if on a vfd and provide you with the proper cfm, if it was engineered prior, something else might be amiss.

That should NEVER be a design issue on a 3 phase motor! They are all inherently reversing regardless of being driven by drives, so the fans need to work in either direction. If you came across something with that as a problem, it was either one of the worst motor designs I have ever heard of, or it was some sort of customized OEM high temperature motor designed for a specific one-way rotation.

This isn't something anyone should worry about with a standard off-the-shelf 3 phase AC induction motor.

Hi, JRaef, I think you missed the point, the fan could be running in the reverse direction. I have seen fans, centrifugal type, being coupled to a motor and being spun backwards. The motor is not the problem, but the sense of rotation of the fan. I know motors are ambidextrous so are centrifugal fans, they are more efficient when spun the proper way.

The motor won't know or be able to tell what hz is is feed with.

We run some at 15 hz to 40 hz. That same motor we ran up to 180 hz.

At high hz the motor don't have enough torque to start a heavy load.

I say run them.

As long as you've got a thermal protection circuit in the motor you should be fine.