[bherr]

Hope someone can help! I purchased a 3 phase vacuum pump on Ebay several months ago and have been busy so didn't get a chance to really hook it up. anyway I started my project today and noticed that the motor is labelled for 50 HZ rather than 60Hz. I did fire the motor up and it ran then popped the breaker. I'm hoping it's because of the mismatch on the frequency. to make a long story short I'm looking for an inexpensive converter that will take the 3 phase 220v 60 Hz and convert it down to 50Hz. anyone out there know where I can purchase one that won't cost me a arm and a leg?????

thanks,
ben

[Geof]

What you are asking for, an inexpensive frequency converter is a contradictions in terms. You would need something that rectifies the incoming 50 hz supply to DC then synthesizes the 60 hz AC from this. In other words a three phase inverter running off a DC power supply or a variable frequency drive running at a constant output frequency; both not inexpensive.

Did you check the motor current and compare it with your breaker rating? The difference in frequency should not make much difference in current draw, and if my understanding is correct increasing the frequency should reduce the current draw because it increase the inductance.

You got it on Ebay; are you sure it is wired correctly and does not have a defect, a shorted winding or something, unrelated to the frequency difference? Check all the windings for resistance leg to leg and leg to ground; I don't know what the values should be but leg to leg they should be the same and leg to ground should have no continuity.

[Al_The_Man]

As Geof mentioned you should not have too much trouble running on 60hz, the difference is it will obviously run higher rpm, this may affect the load, the speed will depend on how many poles it has at present.
If you really want a fix, a VFD should work.
Try and run it and check the current draw both loaded and unloaded.
As you probably know, you just need to block the intake to unload it.
You will need a clamp on ammeter.
Al.

[bherr]

Geof,

Guess I didn't word my post correctly. I have 3 phase 220v 60 Hz power in my shop. the motor I purchased is rated 50Hz 3 phase 220v. I checked the three legs and they all are the same resistance and the legs to ground all read open as per your post. what I need is a frequency convert that will take the 3 phase 220v 60Hx and convert to 3 phase 220v 50 Hz.

ben

[Geof]

You worded it correctly; what you explain it greater detail in your clarification is how I interpreted it; what I answered still pertains.

What is the nameplate current rating at full load compared to your breaker rating? It should run okay just faster as Al says; I do not think it should draw more current.

Just going and getting a VFD, which as I explained is just a frequency convertor, is going to be a waste of money if the motor still pops the breaker.

Is it a single voltage or dual voltage motor and is it wired for the correct voltage if it is dual?

[Al_The_Man]

I think we both mentioned a VFD? This is a frequency converter. You run it at fixed 50hz.
Probabally the cheapest conversion you will get.
What is the HP?
Al.

[Al_The_Man]

Oops, I guess Geof and I both hit the send key at the same time.
A thought, did you try the pump with input and output wide open with nothing connected?
If so the extra rpm may have put it over the top, current wise, I had exactly the same thing happen to me with a impeller type water pump, and this was on the correct Hz.
Al.

[bherr]

Well I fired up the pump again and this time it ran just fine and didn't blow the breaker. the motor is rated at 1725 rpms, with 4.4-4.8 amps. I did notice that the motor plate has both the 60 & the 50 HZ ratings, so maybe Im OK. the first time it blew the breaker a lot of dust came out of the motor. the second time I fired it up, no dust and it ran just fine. guess I'm good to go. Thanks for your inputs guys.

ben

[Al_The_Man]

On 60Hz you will be getting ~300 rpm more

[Geof]

On 60Hz you will be getting ~300 rpm more

???????????? 1725 rpm is the speed for 60 hz isn't it?

60hz x 60 seconds = 3600 divide by 2 = 1800 and take into account slip.

Or am I getting things back-assward?

[Al_The_Man]

Sorry yes, I should have mentioned that 1725 WAS the 60hz rpm.
Which was ~300 rpm more than the 50hz rpm value. .
Al.

[jasminder]

Sorry yes, I should have mentioned that 1725 WAS the 60hz rpm.
Which was ~300 rpm more than the 50hz rpm value. .
Al.

hello there,
I am just wanting to run my 50hz 1hp motor (4 poles) at 60hz. it is giving me 1450~ rpm now at 50hz . i have a vfd so i want to boost up some rpms to get more feedrate on my cnc lathe. do you think that it will effect the torque or life of the motor or the vfd? or should i use a bigger pulley on the motor?
may be i am using someone else's thread so sorry for that but the topic seemed very much similar to me so i thought of a post.

thanks,
jasminder singh

[Al_The_Man]

You should have no problem running off a VFD, I have used quite a few non-vector rated motors with VFD's.
Al.