Power up 3HP Motors using VFD inverter - What speed had you try

Jul 22, 2010
just a question .. i got a 3HP brook motors .

just windering .. what kinda Speed had you guys try on it ..

i have a VFD to adjust the motor speed.

i try 50-60hz .. and it seem fast to me .. i wonder if any guys gone up to like 100 - 200hz or is it safe .

my motors is a 4pole 3 hp . .
the tag said 1420 rmp . 50hz .

i wonder what your speed ?
Depending the electrical system in your country 50Hz or 60Hz will give you the rated RPM of the motor. A VFD will allow you to speed up or slow down the motor, but there is a tradeoff in torque. The further you go from the motor rating the less torque it will generate.

I've never gone over 120Hz on my setup just because I figure that multiplying the rated RPM by 2 is probably fast enough....

I've run mine at 80-100 Hz, and it was FAST. However, after eventually figuring out what deker posted about loosing torque at those high rpms, I set my high frequency on the VFD to match my motor. There wasn't really any need for me to go that fast in the first place.

If you have a belt driven system like I do, you can use different size sheaves to reach higher belt speed with less torque loss while keeping your motor at it's optimum rpm.

Have anyone run it above 150hz - 200hz and if it safe ?

I don't know if it's safe or not, but I wouldn't do it. The bearings in the motor are designed to run at it's rated speed. As with anything, it should be engineered to handle a bit more than that which is why I feel OK running mine to 120Hz. I have accepted the fact that I'm probably shortening the life of the motor somewhat. Now, running 3 times the motor's rating...I'd be afraid of bearing failure, general overheating, and a short like for the motor.

i was at a bearing shop today and seem like most bearing can take speed to as high as 11,000 or more and average is like 5000 - 8000 .

i wonder if anyone had hit higher HZ for your Motor .

cos i was look at guys who go 9000 or 10,000 on their KMG . and if their ratio pulley is 5:2 seem like there got to go much higher then 150Hz . just wondering anyone ?>