Force Cooling in Motors

Dear all,
I need to run 2.2 KW induction motor at 10 Hz frequency or 290 rpm speed. The base speed is 1450 rpm or 50 Hz frequency. I am using OMRON V1000 variable frequency drive for this motor.
I have enabled Electronic thermal overload by setting its parameter L01 = 2 (Blower Cooling) and attach 8 inch fan in place of motor fan cover to cool motor forcefully.
At 10 Hz, motor is taking 4 ampere, so i realized that it is necessary to forcefully cool the motor by installing small panel fan in place of motor fan cover.
It is currently running fine.
Is there any way to reduce the current, so that i can run motor without force cooling????
VFD is currently providing 90 Volts at

I'm not familliar with the omron drive but to run at 10 Hz I would recommend flux vector mode either open loop, or better, closed loop.

Much of the current you are seeing is the magnetising current of the motor and I think that you will need force ventillation at 10Hz.

Nick

probably u need to use gearbox

At 20% of nominal frequency and with self-cooling only, an asyncronous motor can deliver approx 60% of the nominal torque.

A 2.2 kW motor at 400V has approximately 4.8 A nominal current. So I am guessing you absolutely need forced cooling to run this motor at 10 Hz.

Another solution is to select an over-dimensioned motor.

OP running the inverter with load below 25 hz

others possibility STAR or DELTA wiring

osmanmom said:

others possibility STAR or DELTA wiring

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If the OP is currently running the motor in delta at 20% frequency, and it draws 83% of nominal current, then it is not a solution to run the motor in star. The available torque will not be enough.
edit: Running in star, is principally the same as reducing the voltage from the VFD. The motor current will decrease but so will the torque.

OP need to check again what he have done.

What does he have to check ?
The motor is running fine at the moment at 10Hz, and with forced cooling, drawing approx 83% of the current (and thus the load torque is also approx 83%).
The question seems clear enough; is there is a way to reduce the current so that there will be no need for forced cooling.

yes you right

Like said, use forced cooling. one thing though..

ssana168 said:

by installing small panel fan

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I read this as you are hacking the existing cover to apply a fan yourself?
There exist purposely made covers with fans for that.

Increase the voltage. (experts can chime in since I am not one on motors)

http://www.plctalk.net/qanda/showthread.php?t=91839&highlight=supercharging

Unfortunately, there is a ton of bad information in this thread. First, 83% amps is far from 83% torque especially in this small motor. Magnetizing amps is probably around half of that so the actual shaft torque would be less than 40% of nameplate.
Second, 10hz is one-fifth of nameplate 50hz. Many such small motors are capable of 5/1 turndown at full load torque so it is quite likely that this motor will not exceed its insulation class temperature limit at only 40% load torque with no additional cooling at all.
Third, there is no reason to say that a 50hz motor running at 10hz would require sensorless or flux vector control to manage its speed and torque. As long as nameplate slip is tolerable for speed error, V/Hz control would be good enough down to around 4hz.
Fourth, increasing the volts at low speeds by modifying the V/Hz curve has to be done with moderation and extreme care or the motor will saturate and the torque will actually go down as the amps go up.
Not wanting to be completely negative, the suggestion of using a gearbox to shift the motor speed up is a good idea. Or, you could trade out the motor with a six or eight pole version and achieve the same thing without the gearbox.

Is there any way to reduce the current, so that i can run motor without force cooling???

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?

1. Reduce the torque requirement of the load.
2. Ensure the drive is properly tuned to the motor.
3. Add some form of mechanical advantage, such as belt or gear reduction, or higher pole count in the motor.

In truth, as Dick mentioned, it should not be a problem for a decent quality motor, as most motors manufactured today are capable of 6:1 or better Constant Torque Speed Range w/o additional cooling.

Thanks to all,
The heat sink of motor is heating in the range that one can easily grip the heat sink from his hands for a long time. I have not measured the degree centigrade but agree with the dick and bond statements that it can work at 10 Hz speed without the need of external cooling.