frequency 60 hz vs 50 hz

[siva]

Hi
I am Siva working with US Navy, Djibouty. Here I have some problems. We bought some coolers(port-a-cool) from US and those are 110 volt 60 hz. But here we have 230 volt 50 hz. I can use a transformer to step down to 110 volts. I just want to know whether these 60 hz coolers will work with 50 hz frequency? How it will affect its performance? Thanks in advance..

 

[Mr. Bill]

It might be okay, but may not operate at 100%. I've usually heard that 60Hz motors are okay at 50Hz but a 50Hz motor is not okay at 60Hz. I don't know if compressors are an exception to this.

A VFD reduces the speed of a motor by reducing the frequency of the current to the motor. I would look at this like the motor has a VFD that is set at 83% load. Probably less efficient too.

Is buying a new transformer and taking a risk at operating it at the wrong frequency less expensive then buying the right compressor for this situation?

 

[cadpoint]

60 to 50 Hz

60 to 50 Hz

Hi
I am Siva working with US Navy, Djibouty. Here I have some problems. We bought some coolers(port-a-cool) from US and those are 110 volt 60 hz. But here we have 230 volt 50 hz. I can use a transformer to step down to 110 volts. I just want to know whether these 60 hz coolers will work with 50 hz frequency? How it will affect its performance? Thanks in advance..

This is a part of an article that I found on the Net - Via google, using "60Hz to 50 Hz"
The following is parts of the Total conversation, that are directed to your Question. Here the Exact Web Listing. Which is written by an Engineer.

http://www.kropla.com/frequency.htm

....


What happens if you connect a 60 Hertz motor to a 50 Hertz mains:

The motor turns 17% slower

The internal current goes up by 17%
The power (watt) goes down with 17 %
The mechanical cooling is less, because of 17% less turns
The result is a higher current, then designed by the manufacturer and the insulation of the electrical wiring deteriorate much quicker, which after sometime results in a burn-out, which could cause a (the images didn't show up)​

​

.....

Solution:
You can use a transformer to solve part ( the internal current can be lowered but the cycles cannot be changed) of the problem, by connecting the 60 cycles apparatus to a voltage 20% lower as mentioned on the nameplate:
So a 110 volt 60 Hertz apparatus can be connected to a 50 Hertz mains on a voltage 20% lower then 110 volt=90 volt.​

.....

The electrical Voltage and Hertz are different in different parts of the world, roughly you can distinguish:
120 and 220 Volt; 60 Hertz (USA)
230 Volt; 50 Hertz (Europe & Asia) ​

Because the electrical current is dependent of the Voltage and the Hertz you cannot connect electrical equipment with a motor and or transformer in it, to a Voltage other then stated on the nameplate. ​

If you connect 60 Hertz equipment to a 50 Hertz mains the internal current goes up with 17% and can cause a burn-out. If you connect 120 Volt equipment to 220 Volt the current goes up with 100% and surely causes a fast burn-out.
This means even if the Voltage is the same, or if you put a transformer in between to transform the Voltage, you still cannot connect a 60 Hertz motor or equipment with an internal input transformer to a 50 Hertz mains.
A lot of equipment is made for universal use all over the world like a laptop and in that case the nameplate mentions: 110-230 Volt; 50/60 Hertz.​

I hope that this enlighten you enough in your persuits.​

 

[Mr. Bill]

The internal current goes up by 17%

I disagree with this statement. I would say that the current goes down, just like when a VFD is used.

The synchronous speed of the motor is N = 120 * f / p. Typically motors have 4-poles. If we compare 60Hz to 50Hz we get:

N = 120 * 60 / 4 = 1800rpm
N = 120 * 50 / 4 = 1500rpm

Horsepower is dependant on the motor's synchronouse speed and its torque.

HP = (T * N) / 5252

By reducing the frequency of the power supplied to the motor we are effectively reducing the motor's horsepower.

A lot of equipment is made for universal use all over the world like a laptop and in that case the nameplate mentions: 110-230 Volt; 50/60 Hertz.

Most electronics don't care what frequency the supply current is because the power is converted to DC.

 

[72.5kv]

The speed of an AC motor is directly proportional to line frequency. the motor will operate at a slower speed. Stator current will increase due to lower inductive reactance (XL= 2*pi*f*L). higher line current equate to more copper losses and effiency goes down also. V/Hz ration has to be maintain.
this motor would have to be darated.

 

[Cody K]

I disagree with this statement. I would say that the current goes down, just like when a VFD is used.

The synchronous speed of the motor is N = 120 * f / p. Typically motors have 4-poles. If we compare 60Hz to 50Hz we get:

N = 120 * 60 / 4 = 1800rpm
N = 120 * 50 / 4 = 1500rpm

Horsepower is dependant on the motor's synchronouse speed and its torque.

HP = (T * N) / 5252

By reducing the frequency of the power supplied to the motor we are effectively reducing the motor's horsepower.



Most electronics don't care what frequency the supply current is because the power is converted to DC.

I dont know if your calculations are correct or not without looking some things up. What I do know is that we have experienced much higher current when our generators (480Y/277) are generating at lower frequencies. Even a few HZ below 60 will make a significant current increase when dealing with induction motors.

 

[Mr. Bill]

What I do know is that we have experienced much higher current when our generators (480Y/277) are generating at lower frequencies. Even a few HZ below 60 will make a significant current increase when dealing with induction motors.

A supply motor (genertor) may experience higher current when running at a lower frequency because it is supplying a variety of loads. Many are resistive. He was asking about a load motor (compressor).

This is the effect I see on the stator current. You'll need to scroll down about half way. Here.

The stator current decreases proportionally with the frequency, and speed.

 

[Cody K]

A supply motor (genertor) may experience higher current when running at a lower frequency because it is supplying a variety of loads. Many are resistive. He was asking about a load motor (compressor).

This is the effect I see on the stator current. You'll need to scroll down about half way. Here.

The stator current decreases proportionally with the frequency, and speed.

The situation I am refering to is almost all motor loads. Anyway, frequency should not have any effect on resistive loads. As 72.5 Kv posted earlier the motors reactance changes when supplied with lower frequency thus increasing the current.

 

[Terrynistler]

Where is the compressor in this equation? It's a fan motor rated at around 6 amps with water pump rated at around 1.2 amps depending on the exact model they have of course. The water pump and fan motor might see a decreased life span and the fan might well turn at 87% eff. Other then that I am not sure what the discussion got into. I checked there website and they are all rated at 60hz that I could find. Try this contact # to the supplier/manu

Customer Support Corporate Office 1-800-695-2942
Parts & Service Manufacturing Plant 1-888-COOL-AID
Sales Corporate Office 1-800-695-2942

http://www.port-a-cool.com or this link if web is easier. They should be able to give you the scoop.

 

[Mr. Bill]

The second graph shows stator current at 60Hz, 50Hz, 30Hz, and 10Hz.

I don't know how to attach this picture directly to this forum.

 

[LarryFine]

The second graph shows stator current at 60Hz, 50Hz, 30Hz, and 10Hz.

I don't know how to attach this picture directly to this forum.

Allow me.

​

 

[Bob NH]

Where is the compressor in this equation? It's a fan motor rated at around 6 amps with water pump rated at around 1.2 amps depending on the exact model they have of course. The water pump and fan motor might see a decreased life span and the fan might well turn at 87% eff. Other then that I am not sure what the discussion got into. I checked there website and they are all rated at 60hz that I could find. Try this contact # to the supplier/manu

Customer Support Corporate Office 1-800-695-2942
Parts & Service Manufacturing Plant 1-888-COOL-AID
Sales Corporate Office 1-800-695-2942

http://www.port-a-cool.com or this link if web is easier. They should be able to give you the scoop.

If the motor is driving a fan or a centrifugal pump or compressor, the head or pressure will vary as the square of the speed, the flow will vary directly as the speed, and the power required to drive the fan or pump or compressor will vary as the cube of the speed, or about 58% for 5/6 speed.

If it is a centrifugal compressor in a refrigeration system it will probably not produce enough head/pressure to operate the condensor.

If it is a positive displacement compressor the displacement should be proportional to the speed and the torque required to drive the compressor should be about the same because that depends on condensor pressure. Since torque required of the motor is about constant, the current in the motor should be about constant and the power should be about 5/6 of the case at 60 Hz.

 

[Limey Pete]

I've seen quite a lot of different opinions on increased current or decreased current on this post but very little about the type of motor in question. My problem is that in stating my "opinion" some of my English terminology may be a little different but;
If it is a Squirrel Cage Motor (Induction motor pretty much) Current will increase significantly. and speed will decrease by 17%.
If it is a Universal motor (pretty much an electric drill type motor with brushes); current will decrease because of the Back EMF (reverse generated electricity) produced in the rotor. It might also be a Series wound or Compound wound motor with other possibilities to the final current on either the rotor or stator windings. I don't know how much of my language is "universal" here?.

 

[beanland]

Port-a-cool

Port-a-cool

I looked up the product and they are evaporative coolers. No compressors. Just motors and pumps. A 115V 60Hz motor will run fine, but slower (1500rpm vs 1800rpm), at 92V and 50Hz. (Like a VFD but constant V/Hz ratio.) Use a transformer to step the 230V 50Hz to 100V and it should run, not great, but OK.