Refrigerator induction motor: peak current draw

[dcmeigs]

Re: Refrigerator induction motor: peak current draw

Thanks. The fridge I have now is a Whirlpool and it is in its 14 year now. It's having trouble starting and I have again replaced the start relay with a 3in 1. It's located in Phoenix and has spent months at a time running in an un-air conditioned house during the summer when I'm away. All in all I have no complaints. I'll shop for another Whirlpool.

[delaware74b]

Re: Refrigerator induction motor: peak current draw

Best refrigerators made right now are Whirlpool or Frigidaire (or Kenmore models that start with 106- or 253- model prefix.

To add insult to injury, Electrolux bought GE's entire appliance division this year and Maytag was bought out by Whirlpool a couple years ago. So, Maytag is now 90% Whirlpool parts with a Maytag name plate.

[dcmeigs]

Re: Refrigerator induction motor: peak current draw

It seems people here have strong opinions on refrigerators here. There is a general agreement that GE fridges are crap and the local appliance parts shop encouraged me to buy either a Samsung or LG because their parts business on those brands was so strong they were putting his kids through college. I visited a consumer web site and not a single manufacturer ranked higher than a single star.

Soooooo, I need a new fridge and don't want to buy a POS. Which manufacturer is making a good product these days?

[sam_sam_sam]

Re: Refrigerator induction motor: peak current draw

Running refrigerators on a generator can be done how ever is hard on the compressor and if that compressor is on it's last leg it will finish it

If you need to Running refrigerators on a generator and have the time to do it put a hard start kit on the compressor that will help a lot

[kc8adu]

Re: Refrigerator induction motor: peak current draw

not long ago they were rebadged motorolas!
as good as electronic ballasts got.
now they are all shit.

I wish I had taken pictures of their electronic ballasts I replaced a few years ago. Cap failures, blew the covers off the ballasts, Chinese made for GE.....

[delaware74b]

Re: Refrigerator induction motor: peak current draw

That's odd to lose equipment like refrigerators on a generator unless there was some problem with voltage or frequency regulation.

I had operated 2 21cu ft top-freezer refrigerators and a small upright freezer on my 3KW (continuous) 120-volt-only generator for 6 hours and never had and issue. In fact, I still have one of the refrigerators and the freezer.

[eccerr0r]

Re: Refrigerator induction motor: peak current draw

Figured out exactly why? People have been running generators for refrigerators for a long time. Unless the generator was screwed up and sent 220V to the refrigerator or something like that causing the compressor motor to overheat, that doesn't make sense to me.

[berniedd]

Re: Refrigerator induction motor: peak current draw

Maybe you need more than a 1KW generator. I remember in the early 2000s when we had a power blackout for 4 days. On day 3, I desperately needed the ref (220 watts) to cool the food I'd stashed in there. So I connected it to my 1500-watt single phase generator (no other appliances connected, just the ref). After 15 minutes, I turned 'em both off. When power was restored later, the ref wouldn't start. The compressor was found to be shorted, and I had to get it replaced.

[lti]

Re: Refrigerator induction motor: peak current draw

I tried to repair a dead GE microwave (made in 2008) last year. It was made in China by Daewoo for GE. It was replaced by another GE microwave.

[delaware74b]

Re: Refrigerator induction motor: peak current draw

The 1/5-hp motor is the condenser fan motor (the one on top of the a/c unit). It also draws the 1.1 amps on 240 volts. Most outdoor central a/c units(except the Sanyo and Mitsubishi) are 240-only units.

The 16.4 amps rating is only for the compressor. Also, the minimum circuit size is calculated at 125% of the 16.4 amps (compressor) + 1.1 amps (fan motor) = 20.5 amps. NEC allows next breaker size (25 amps on #10 copper).

GE = garbage electric. I'd never own any of their side by side or french door refrigerators. Quality and electronics so bad they've contracted LG or Samsung to make them for GE. Add insult to injury, LG and Samsung pulled all 3rd-party technicians' certs for repairs. They want to do their own warranty and out of warranty repairs. Good luck if you have Lg or Samsung appliances. The only thing I have seen reliable from GE is their motors. I wish I had taken pictures of their electronic ballasts I replaced a few years ago. Cap failures, blew the covers off the ballasts, Chinese made for GE.....

[eccerr0r]

Re: Refrigerator induction motor: peak current draw

An example is how it could pull 4A w/o a run cap yet consume ~180W- 1.5A if unity power factor.

With a run cap compensating the phase shift, it'll consume that same 180W, but at quite a bit lower current.

Ah, so it is possible if the run cap is fried, it would consume more apparent power as its PF would go down. Or would it simply not turn over anymore with a weak or bad run cap?

[kaboom]

Re: Refrigerator induction motor: peak current draw

Ah cool never would have recognized those acronyms, i'll have to go look.
Strange that motor is only 1/5 HP, and 16.4A@120VAC is a lot more than 1/5 HP...

Sounds like LRA. FLA, or actually RLA since this is a hermetic, is probably from 2-5A. It'll be on the lower end of that if it's got a run cap, which will turn it into a PSC motor and also reducing the current drawn for a given wattage draw.

An example is how it could pull 4A w/o a run cap yet consume ~180W- 1.5A if unity power factor.

With a run cap compensating the phase shift, it'll consume that same 180W, but at quite a bit lower current.

LRA= Locked Rotor Amps
FLA= Full Load Amps
RLA= Rated Load Amps (Not "Run Load Amps!)- Applies to compressors.

Don't mistake for "Run load amps" because an HVAC compressor does not always "run" at full load/current.

Rather than jumble what others have already said, here's a link:
http://hvac-talk.com/vbb/showthread....RLA-verses-FLA

[eccerr0r]

Re: Refrigerator induction motor: peak current draw

Ah cool never would have recognized those acronyms, i'll have to go look.
Strange that motor is only 1/5 HP, and 16.4A@120VAC is a lot more than 1/5 HP...

[kaboom]

Re: Refrigerator induction motor: peak current draw

Do modern refrigerators now use electronically commutated compressor motors now? That's something I haven't heard of before, not sure if it's that or just pure insulation that gives modern refrigerators its low power requirements.

Oh this is a good point- I almost forgot about this completely.

Stay away from GE! Any of their fridges with that "access panel" on the back behind the fresh food compartment (Arctica, others) use an SMPS deliberately designed to fail within a year from bad/fakecaps.

The whole machine depends on this, depending on "features," in one way or another.

The temp controls are on a board just inside the door are all digital, with a com interface to the main board. When temp control board first gets its 12V supply, its MPU sends a pulse train talking to the main CPU, apparently for the ADC'd values of the fridge and freezer temp. Upon receiving this data, it gets converted to the "1-9" temperature number displays; or on middle models, the actual temperature is displayed.

When changing the temp, the small display board comm's to the main, "commanding" it to change setpoint(s). Remember, there's yet another section, either on the main or individual boards, containing thermistors, in the fridge & freezer, which talk to the main.

There are "monitor" switches for both doors that generate interrupts for the CPU. This data is used to determine the cycles-per-hour, defrosts-per-day, and, of course, turning the lights on and off. There are stepper-motorized dampers, like on auto instrument clusters, to control dampers in the ducts between the evap, freezer, and food compartments, also controlled by CPH/door openings.

IOW, we run "algorithms" in our "fridge."

All fans are 12V-PWM controlled, and similar to high-performance computer fans. Basic models power everything from the derived supplies of that shitty SMPS, except the lights, defrost heater(s), and compressor.

"High end junk" models have a variable speed compressor, a 'la Carrier, but unlike a real HVAC system, the power board for the GE compressor is almost as bad as the SMPS/main.

If RoHS doesn't kill the VFD, the comm link between it and the main is fried when (not if) the Hermeis die.

And they claim the VFD-compressor "saves energy." A proper implementation will, with an easy to clean condensor coil, but when the "barrel coil" condensor clogs and the POE cooks, you throw food away. And there's the "minor" issue of replacing boards every now and then...

GE= Garbage Equipment

Not any surprise really, they're just a vector for money, disguised as "appliances," and even more so after Holder and Soetoro's "leveraged takeover."

http://forum.appliancepartspros.com/...ain-board.html

From my understanding, these things keep a local appliance store (Good's) quite busy. They're always doing board swaps (at least) on warranty fridges. Look at the board in the link- it's quite deliberately and well designed with the layout, SMTs, etc- do not tell me those "Na-circle" and Ltecs are there "by accident."

[delaware74b]

Re: Refrigerator induction motor: peak current draw

Is there a LRA (locked rotor amp) rating on the compressor? It will be several times higher than your running amps. The LRA will be in the circuit for the first second or 2 during start-up.

For example. I attached the data tag of the outdoor unit of my 3-ton a/c system. At 93 amps, the LRA is 5.5x more than the RLA of 16.4 amps (running loaded amps). The thing to remember is motor loads are inductive and have short-lived high current start-ups.

[eccerr0r]

Re: Refrigerator induction motor: peak current draw

The inverter is modified sine wave, which may add additional issues.

I think my fluke 77 does have a peak hold function but not sure if it can deal with the current...

[budm]

Re: Refrigerator induction motor: peak current draw

Is your inverter putting out sine wave or step/modified sine wave?
Can your meter do peak hold? I use my FLUKE 87 and CT for capturing peak current after period of times.

http://www.theinverterstore.com/tips.html
http://www.powerstream.com/inFAQ.htm

[eccerr0r]

Re: Refrigerator induction motor: peak current draw

It is an issue when dealing with designing minimalistic backup power sources.

Grid power is plenty, but when the grid goes down and you have to resort to backup power - whether a generator or a battery system - getting past that hump makes a big difference on whether or not your stored food goes bad.

I still do not have a DSO nor a CT to measure, but based on just a DMM I can tell the voltage droops a lot during startup, and the inverter gives up trying to supply enough power to run the motor.

Do modern refrigerators now use electronically commutated compressor motors now? That's something I haven't heard of before, not sure if it's that or just pure insulation that gives modern refrigerators its low power requirements.

[Longbow]

Re: Refrigerator induction motor: peak current draw

Aside from the academic question of what the motor start current is, I am missing the importance of why it is an issue? Motor starting on a compressor might take all of one second, so attempts to minimize start current would be pointless unless it was so large that it was tripping the breaker. Start current for a specific motor type under a known load really can't be "improved" because the motor has to generate enough torque to start rotating and move the load during the starting process.

If you can get a digital storage scope hooked to a current clamp, you will easily see what you are looking for - let us know if you get this info. The trend in everything right now is to use brushless motors with imbedded electronics. At neat improvement in motor operation at triple the price.

[eccerr0r]

Re: Refrigerator induction motor: peak current draw

Well, I don't think I can get refrigerant for it anymore, nor parts... but who cares, until it breaks

I just was a bit dismayed my 300W AC inverter wasn't enough to overcome startup power of the refrigerator. Just wonder how much more is needed...