Note that when speed is raised above the base speed of 50Hz motor, a vfd operates the motor in constant hp mode ie torque is reduced. This is also done to try to satisfy the NEMA specification that at 100% output torque, the general purpose motor voltage variation be within +/-10%. But in OP case both torque and speed rise at 60Hz. So motor issue would happen.
400V 50HZ operate on 480V 60 HZ
- Thread starter td1313
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kwired
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If this is VFD driven then the drive should be programmed to running a 50 Hz motor at the 400 volts instead of a 60Hz motor at 460 volts. May not be as possible if it is a OEM drive vs a general purpose drive though.
Why? Please clarify.
electrofelon
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For example this one at a current project of mine:
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zbang
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From post #1-
a 400VAC 3PH 50 HZ motor
Running a 50Hz motor on 50Hz should be fairly normal.
What this means please?:
"May not be as possible if it is a OEM drive vs a general purpose drive though"
zbang
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Some VFDs have a parameter for the motor's rated frequency, some don't; same for rated voltage. For instance, the Westinghouse/Teco L510 allows you to set the rated freq at 02-06 but only read the rated voltage at 02-04.
VFDs tend to have quite a lot of parameters.....
VFDs tend to have quite a lot of parameters.....
kwired
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Because many OEM drives have limited functions that can be field set - they were designed for a specific application.
General purpose drives will likely have more options as they can be configured for wider application use.
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No need to confuse this with the VFD part of it. The V/Hz ratio is the same, so the motor torque will be the same. For a lot of companies that make IEC designed motors and want to sell them in the US, they just change the nameplate on a 400V 50Hz to read 480V 60Hz.Of course. Sorry about that, I hadn't had any coffee today yet.
What I should have said is:
The Volts/Hz are the same, and so it would be like running a 50Hz motor with a VFD in V/Hz mode at 60Hz (but minus the switching noise, etc.).
I believe the torque and current characteristics should be about the same at 60Hz 480V as at 50Hz 400V,
The motor will run 20% faster than it would have in a 50Hz country, but you are replacing a 60Hz motor anyway, so that’s irrelevant. It’s fine, no need to be concerned, UNLESS the HVAC mfr was utilizing the Service Factor of your 460V motor. IEC designed motor do not have a Service Factor, or looked at the other way, they are all have a 1.0SF. That’s a question only the HVAC mfr can answer.
drcampbell
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Are you replacing the entire condensing unit, or just one motor?
Turning a fan at 120% of its design speed will consume between 144% and 172.8% as much power. At best, it will be noisy and waste energy. At worst, something will break and/or the motor will fail prematurely.
Turning a compressor at 120% of its design speed will pump ~120% more refrigerant. The condenser and fan will then be undersized, throwing the system out of balance, resulting in higher temperatures and pressures that probably will result in premature compressor failure.
If the entire unit will be replaced, the relays and transformers inside will be operating at 120% of their design voltage, resulting in higher currents and temperatures.
But the cost of premature equipment replacement will pale in comparison to the cost of wasted energy. HVAC consumes a LOT of energy; any sort of Appalachian Engineerin' that reduces efficiency will be very expensive in the long run.
Bring in a mechanical engineer for a consultation. HVAC equipment is almost always oversized and a smaller unit may very well provide adequate performance. (and also energy savings)
This is not possible with a fan motor. If you turn a fan at a higher speed, it will consume more torque and power. Either the motor will supply the additional torque & power, or it won't turn at the selected speed.
kwired
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He is just replacing a 60 Hz motor with a 50 Hz motor but plans to run it at same speed as original so the driven load won't see any difference, the question was can the 50Hz motor take this?
drcampbell
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When making a substitution like this, the mechanical considerations of operating at a higher speed need to be considered. It's not merely an electrical question.
electrofelon
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Doc, I think you are not understanding, speed is not changing, go back and reread the OP.
winnie
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What type of motor are you replacing (blower, pump, refrigerant compressor)?
What is the rating of the original motor?
What is the rating of the replacement motor?
If you are replacing a foot mount or face mount motor with one that has the same pole count and torque rating, the nominal 50Hz motor will probably work fine in the 60Hz application. It will run at higher speed than designed for, but the % change is small and when the motor is used at the same torque and V/Hz value it will not be subjected to excessive current or heating.
But if you are replacing a non-standard motor or a motor contained in a larger module, all bets are off. A 50 Hz hermetic compressor will be operating at higher speed and will have different compression characteristics. A blower _module_ consisting of motor and fan will be operating at excessive speed.
-Jon
kwired
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Mechanical considerations of the motor could come into play, but I doubt going from 50 to 60 Hz is going to be too big of a deal, Going from 50 or 60 Hz to 400 Hz on the other hand...
Again driven load in OP will still have same speed when all is said and done so driven load is not impacted here.
I went back and read it for the third time. All I see is that he’s replacing a 60HZ unit with a 50HZ unit. No mention of speed or if a VFD is involved.
Well done that man !
electrofelon
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Right, replacing with a 50hz unit BUT RUNNING AT 60HZ
winnie
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Right, the OP has not been heard from, and we are all guessing what is going on, and making assessments based on our assumptions.
I read the post as saying that a motor in a condensing unit was being replaced. But others apparently read that the entire condensing unit was being replaced. Very different situations with very different results.
We need to sit back and wait for the OP to come back and describe what exactly they want to replace.
-Jon
I read the post as saying that a motor in a condensing unit was being replaced. But others apparently read that the entire condensing unit was being replaced. Very different situations with very different results.
We need to sit back and wait for the OP to come back and describe what exactly they want to replace.
-Jon
Thanks everyone who has responded. I wanted to add a little more detail, based on the responses so far. There at 2 condensing fan motors on the condenser unit. The primary motor is controlled by a VFD and the 2nd motor, the bad one, is pressure controlled and cycles as needed. The increased speed caused by the hertz difference should not be a problem because there is a 300 rpm difference anyway, the fan may cycle a little more often but not an issue. And yes I know the motor is at risk of failure but I’m at risk of losing a data room HVAC system. The amp ratings are also similar so I’m not really worried about overloading a breaker but will obviously monitor while running.
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