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What happen if a compressor rated as 50HZ 230vac were hook up to a 60Hz 208/230vac.
does it run slower? faster?, overheat? loss effiecency?, gain efficency? or does it matter... no problem at all?
I never done it, but always wonder what would happen.
I believe faster and with higher amperage. Most likely hotter. If you had a 230/50 compressor hooked up to 200/60, you would run faster but not hotter, which leads me to believe that there would be about the same wattage in the latter case and a higher wattage in the former. These are just guesses. I don't know what the behavior would be with capacitor run motors, for example.
Dan
I am from Canada and once on a European fishing trawler I had to install a 3 phase motor I believe it was 60 hp. It ran faster. The compressor was running above the engineered specs for rpm for the compressor(Sabroe).To compensate I used a smaller pulley on the motor.On a hermetic the compressor will run faster as well so the compressor discharge temp will be higher so it could be trouble for the oil carboning up and breaking down.
I deal with a lot of overseas equipment here in the US. The newer equipment is 60 hz. The 3 phase 50 hz stuff I have successfully used, however, I was told a very long time ago as long as the use was not continous I wouldn't have a heat problem.
Good Day SIr!
Its one of my problem here... But it goes by a Cascaded Syatem using R-404A and R-23. Its a Thermal Shock (Temp. Cycle) machine came from Malaysia at 50Hz and was transferred here in the Philippines and we are operating at 60Hz. At running condition, compressor stop intermittently with an erratic pressure readings. Though it run, still, it couldn't reach the required Temperature Specs of -65 deg. C... Please help what should I need to do...
Thanks in advance,
Rac'ers 98
Hi, wong. As I know, some of the compressors can work well at either 50Hz or 60Hz, and the discharge/capacity will be increased of 20%. U can ask the manufacturer about this question.
RAC'ers 98, ur issue could be due to the increase of discharge. the cascade system may need redesign.
Thanks Sir!
Would it be helpful if I will only replace the 50Hz compressor with 60Hz rated frequency? Do you think it will solve the issue or I need to redesign the whole cascade system???
Appreciate all the help... and thanks in advance...
What do you mean with erratic pressure readings?
LP or Hp and on what side?
We need a lot more of information to help you.
Give us numbers: SH, SC, LP, HP, discharge temperatures and this of both stages.
A cascade system is a very well balanced system which can't be changed very much.
Changing to 60 Hz is in increase of +/- 20%.
Hi, RAC'ers 98, you're welcome, I consider it's a short cut to replace 60Hz compressors which have the same capacity of these 50Hz ones. If not, the whole system would be redesigned.Quote:
Originally Posted by RAC'ers 98
A 60 hz equipment can run on a 50Hz, but a 50hz equipment cannot run on a 60hz, motor will produce extra heat, thus shorten the life of motor.
Using the fan speed formulaQuote:
Originally Posted by Cofreth
RPM = [[frequency x 60]/pole pairs] - friction factor (4% normally)
we can see that a 50hz, 4 pole motor driven by 50hz would give a speed of
[[50 x 60]/2] - 4% = 1440RPM
Now, if the same motor was driven by 60hz you would get
[[60 x 60]/2] -4% = 1728 RPM, an increase of 20%. This increase will lead to additional current draw and heat being generated which will decrease the life of the motor.
Quote:
Originally Posted by Peter_1
Good Day Sir Peter,
My apology for a lacking info...
Erratic Pressure reading means for me that the gauge display or the pointer movement is not normal. Its a kind where the gauge hand looks like vibrating and its not pointing on an exact pressure value. Anyway, I will try to get all recorded data the ASAP and will get back here for a discussion with your great support likewise.
Thanks also for the rest of the advisers... Sir Ernestlin, Sir Frank and Sir Cofreth... APPRECIATE ALL YOUR HELP...
Regards,
Rac'ers 98
This is where the gauge is reading the compressor pulsations. Get a set of damped gauges to stop it.Quote:
Originally Posted by RAC'ers 98
Very Interesting, I am surprise Counter EMF does not come into play.Quote:
Originally Posted by frank
I have fitted a number of 50hz fractional compressors into a 60hz situation. (Embraco and Copeland) I have always downsized the compressor to what was originally fitted. Had one failure so far. I don't have a choice about this as there are no 60hz compressors in the country.
Just goes to show that the internals of a motor-compressor are very forgiving!
What does Nz run on? and why are 60Hz scarce?
Frank is right , the speed will increase proportional with the frequency.Quote:
Originally Posted by frank
But a higher speed of the compressor with the same evaporator connected to it will result in a lower suction pressure, so a reduced motor current which will balance the higher speed.
Is this statement correct? This is some sort of a brainteaser.
Peter,
I think you are going in the right direction with your logic.
If the compressor speed increases, it's displacement increases too. That would result in a lower suction pressure and a higher TD to increase the coil capacity to cause a re-balance.
New Zealand is 230V 50Hz or three phase 400V.Quote:
Originally Posted by The MG Pony
The reason for the 60Hz application is a ferry I look after.
I was asked to fit A/C to two theaters on this ship.
I asked many people what would happen when a 400V 50Hz inverter machine was connected to 60Hz.
"Motor would burn out" / "electronics would not be able to control the temperature" etc.
Finally two knowledgeable people said "no problem"
They were correct, this system has worked A1 since installation.
Most 3 phase motors nowadays come rated for both, however, you could always buy a little vfd and knock the freq back down to 50 if 60 is too fast.
we have to ask electrical engneer to give us more information in detail
In my opinion , if the power consumption is the same , the couple decrease when the speed increase and the motor work better at 60 Hz. We have problem if the motor for 60 hz works on 50 Hz .
Here is something interesting; This compressor is on ebay. Notice this compressor take both 50HZ and 60HZ different voltage.
" Both are 380/420 volt-50Hz 460Volts-60Hz 3Phase 5HP 50,800 BTUH R-22 The Numbers on metal tag are AGC5561EXG and AG133UT-0003 Buyer responsable for shipping ! These units are 100 lbs each! this auction is for one of the compressors."
Can someone explain to me; how do they wound this motor? How many poles?
Allmost all compressor motors, I believe, are rewind on 1 pair of poles. That is, at 50Hz they rotate 3000 rpm minus "slip", or "lag", or "friction" (difference between rotating field in the stator and the actual rotations per minute).
60 Hz motors rotate 3600 rpm - the slip.
The only explanation I can come with for an (asynchronous) motor able to work both 380 -420V 50HZ and 460V 60Hz is its universality.
But universality does not mean that at the same load but different voltages and frequencies it will have the same speed, draw the same current, be able to produce the same work. It is rather something averaged around the numbers which the manufacturers specify.
To put it short, at 380V 50Hz the motor is slowest and lest powerful. At 460V 60Hz the same motor is quickest and most powerful.
By that, the slip will be maximal at 380V 50Hz - let's say 7 %, and minimal at 460V 60Hz - let's say only 2%.
Generally most compressor manufactureres will supply compressors for dual HZ ratings with-in a particular voltage supply range. check name plate ratings. Obvious really, why supply two options, economy of scale production wise.
At 60 HZ it will run faster, higher swept volume.
magoo
Another explanation I could offer to account for a tolerable work of a dual-frequency motor is the construction and the alloy the steel plates in the stator and rotor are made of. At the greater frequency the motor exerts greater impedance. The resultant current at 460V 60Hz does not differ substantionally from that at 400V 50Hz. Neither the slips nor the rpms.
No, rather the slip at 60Hz is greater. But the current and the rpm almost the same.
Quote:
Originally Posted by dan wong
For the same voltage 230V with the increase of the frequency the torque (N.m) decrease. If the voltage also decrease (208V) the torque decrease even more (it decreases with the quadratic voltages ratio).
The motor will be away of the syncronism velocityand the current (A) will be higher and will be hotter. Of course if the resistent torque at the compressor shaft is very small for the lower motor torque so it would happen nothing special at all and the compressor would run near the syncronism velocity, near the nominal operating point of the motor.
Attention should also be taken at the starting of compressor because the lack of the motor torque it could notlet the compressor rotate. Check if the compressor is total unloading during the firsts seconds...and maybe a DOL (direct on line) start would be needed...
Regards