460v motor

The motor nameplate gives the motor's characteristics. Your motor will be capable of producing 1.5HP if supplied 460V at 60Hz.

Supplying less voltage will distort the voltage/freq characteristic of the motor. The motor will still run, unloaded at nameplate speed, but will not supply rated torque. If your application only requires 0.5Hp you will probably be ok. It is important to use a thermal overload device to protect all motors, size it for the motor nameplate amps, regardless of the applied voltage. Be aware that you can easily step up the 380VAC to 460VAC using a transformer. Based on 1.5HP this would only cost a couple of Hundred dollars (US) May be cheaper than new 380Vac motor

The torque output capacity of the motor will decrease by the square of the voltage reduction. You will only get roughly 68% of the normal torque out of that motor, which means that effectively, it becomes a 1HP motor at best. Any loading in excess of 1HP will cause the motor to slow down, increasing slip and it will draw excessive current, overloading long before it normally would. So if you do not re-size the OL protection, you will likely burn up that motor. You can try to recalculate the effective FLA by using the 1HP at 380V and a .8 pf and 80-% eff., but a chart I have shows a 380V 50Hz .75kW (which is about 1HP) as having a FLA rating of 2.0A, so I would use that.

I see, the motor i said is 220/460 3ph. can i use the 220 and still deliver the 100% torque without reduction?

Sir,

If you mean "can I use the 220v winding at 380v . . ?", the answer is NO! The much higher voltage will burn out the windings in less than one minute. If you have an overload relay set for the proper low-voltage current, it will trip in a few seconds at most.

As noted by others, the motor is rated for 460v at 60Hz. Since the ratio of voltage to frequency should be constant, supplying the motor at 380v requires a desired frequency of 380/460*60 or 50Hz. Thus a 50Hz application will work well with this motor at the 380v you stated. However, the output torque and power rating will both be lower. If you need the full rating of the motor, the only way will be to use a transformer to increase the voltage. A VFD (mentioned by one person) will not have a high enough DC bus voltage to supply the required full 460v waveform.

Sorry--JMM

220 volt motor at 380 volts....It'll cook and fail...very quickly!

"I see, the motor i said is 220/460 3ph. can i use the 220 and still deliver the 100% torque without reduction?"

Yes, IF you have true 230V power available. Do not connect the 380V to this motor with a 220V connection. Also, because if it is a 230/460V motor it is a NEMA design, so it cannot be connected in Star as you could with an IEC dual voltage motor. So although you may have 380Y220V available, you have no method of internally connecting that motor so that it will see only 220V; it has no neutral connection point internally that would be valid for this.

No you can not.

This is a 3φ phase system. your 220V is single phase out of 3φ 380v system.

Wangito.

So if you do not re-size the OL protection, you will likely burn up that motor

Standard overload elements trip on current. The overload in this situation should be sized for the motor nameplate amps (regardless of 380/460V) Standard OL charts rarely have a "Voltage" column. Amps are amps, and the motor will not burn up until the amps exceeed the motor nameplate.

Were he operating this motor at 380V 50hz, then you would be correct, but he said 380V 60Hz. The V/Hz ratio is incorrect for this motor design.

The time curves for OL heater element responses are based upon an assumption that the motor is getting proper V/Hz ratio. By having a significantly lower voltage like that, the motor will be operating in saturation long before the current rises high enough to cause a trip at the normal nameplate FLA. So the heating created by a given amount of current in an already saturated motor is greater than at a proper voltage level, meaning that the motor damage threshold will be much much lower.

You understand motor theory, and your original post is very accurate. But with regards to the overload, what you are suggesting should be posted on the "Free Energy" blogs.

Yes amps cause heat in numerous ways, such as I²R and heating as a result of hysteresis. But no matter how you slice it the amps must travel through the overload to generate the heat, and the amount of heat to 'burn up' a motor is a constant value regardless of V/Hz.

The motor's total amps I_t are calculated by the following: I_t=SQR( I_z²+I_q² )

where I_z=Magnetizing amps and I_q=Torque amps.

Typically motor of this size will draw approx 55-75% of it's rated current at no load, and the stator should already be saturated. Thus I_q = 0 and I_t=I_z

As you load the shaft, the motor speed decreases, causing I_q to rise, which is reflected in a rising I_t. The mismatch in V/Hz only causes this rise to be quicker for each ft-lb of added load. This means that the motor will over heat at a lower ft-lb of loading, but not at a lower I_t

EXAMPLE: Imagine a properly powered 2Hp motor connected to 3HP of load.

We size the OL to trip in 1.5 minutes.

Now we reduce the voltage, which effectively de-rates the motor to 1Hp.

It will now trip the same overload (in 1.5minutes) when the motor is connected to 1.5Hp of load (not 3hp), because this motor now requires extra OL amps to run the 1.5HP load. Either case I_t is equal when the OL trips.

What happens during brown outs? Fires or OL trips?

OK, Mevel123 that's a good argument, I'll concede your point if you explain this to me.

I was thinking in terms of the effect of having the same load on the motor and having the V/Hz ratio keep it in a saturated state, but you are right, it should be irrelevant as long as the overall current passing through is below the FLA rating. In my mind however, I was thinking of this well known and accepted chart without looking at it, assuming it had a saturation curve on it. Now that I found it and look at it, it does not; I guess I was thinking of the efficiency curve.

So explain how as the current goes up with a voltage reduction, the efficiency goes down. That to me means more of the energy going to the motor is turning into heat, not useful work. So according to this when there is a severe voltage reduction, the heating effect per amp consumed is higher than at rated voltage. And this chart doesn't even show what happens below a 15% drop: 380 on a 460V motor is >20%! That was why I was insisting that to properly protect the motor during a continuous reduced voltage state, you would need to reconsider the power rating of it to be lower than what the nameplate says.

The timing on this thread is absolutely perfect. I have a note that I wrote myself on Saturday to chase this exact issue.

Plain and simple...reduced voltage on the high voltage windings will prematurely burn up the motor. I have a very fried 10hp motor sitting 5ft from me that is a nice example.

I have a spiral freezer box with 850'x5' stainless belt run by a 10hp bull drive and 2hp tension take-up. Four months ago I spent $150k for the manufacturer to come in and replace the belt, all UHMW, bull chain, and a couple of corroded out disconnects. Included was new chunks of flex and wiring to the motors.

Since then I have had nothing but problems. Very hard starting even though I run the motors on this with Flex70 drives. Higher than normal starting amps...stalling on cold restarts with loaded belt. And a few etceteras. Had the OEM back in twice. Their tech even went so far as to tell me we must be freezing the belt. DUH! It's a -30°f box.

Last Friday night it stalled on a restart with 7000 lbs in it. I came down...had a h*** of a time getting it going. Tension drive was tripping o\l...Flex was faulting on stall (but never on overcurrent). Got them running, finished production and dove in Sat. morning. Checked every bearing..every nut and bolt...strain gauge on the belt...nada. Then I happened to find the 10hp motor REALLY hot. In -30° it takes a HOT motor to burn you through gloves.

On opening the peckerhead I found that when they had rewired my motor they were gracious enough to reconfigure it for me to 460 even though I have a 230v drive ... and they built it. The motor is FRIED. Just barely megs enough to keep it from spitting fire.

Other than higher starting current I never saw it. Normally...running fully loaded I see about 50%ish on the ammeter...14 to 15amps (230v). Last 4 months...we've been seeing 14-15amps. But that is 100%+ current if you were hooked up on 460.

Anyway...good timing on this thread...

Bummer. Been there, done that. I once had to fly from Seattle to Boston because "your drive was making the motor lose too much torque and it's stalling". Fiddled with it for 3 days before it dawned on me to check the motor strapping. I had wired the motor at the shop for testing before it shipped, but the field electrician took it upon himself to reconnect the motor when it arrived. Never found out why but I never got paid for the plane fare either.

AH! A concession with a condition Sounds like a trap to me...

The power factor shifting is the main reason you can have extra current without causing heat. What is happening during the reduction of voltage is the amps and voltage are becoming more and more out of phase with each other, meaning you need more amps to do the same work, including waste heat. This helps our simple overload, since the OL is assuming a unity PF, and will trip on amps, not effective watts.

Imagine this - You have a DC motor on a drive running full speed no load. (ignoring amps due to mechanical losses) You measure 500VDC and 0 AMPS. Watts = 0. This makes sense because you are doing no work.

You upgrade your machine to AC, and now you notice when running motor at full speed no load you measure 480VAC and 55% nameplate current- Did you get ripped off? No, you are just circulating currents due to what is similar to a "Tank Circuit" effect. The amps produce Flux, flux collapses and produce amps. Since no current is being induced into the rotor, you are not actually doing any work and Watts = 0. If these amps were producing heat there would be watts lost.

Proof is that both the AC and DC drive will show 0 amps on their input when not loaded. (Again ignoring losses)

I think your chart is showing a fully loaded motor, and how reducing the voltage kills the efficiency of the magnetic transformation required to induce torque in the rotor.

I do want to state that regardless of the theory, or overload sizing, professionally I would never allow (nor would most local codes) a motor to be wired to the wrong voltage source. I should have stated that in my original post, instead of leaving the door open.

No trap, just always looking to improve my understanding. I received very little education on motor theory in school (and that was a long time ago) because at the time, everyone was having us focus on the emerging field of electronics and micro circuits (this was before the divergence between Power and Electronics Electrical Engineering that we see now in college degree programs). Consequently, most of what I know about motors and motor control has been attained through on-the-job self education (and a few carefully studied catastrophes!).

Thanks for the extra time you devoted to that.

Good advice, technically sound answer.

Why do you have 380 V a/c?

Most common power designs for industrial / commercial buildings is 3-phase, 120/208; 120/480; 277/480.

380V a/c is not a common supply of source voltage. If you supply a 480V rated motor with only 380V, it will short live the motor. Your motor will burn itself up in less then its rated half life. At 380V input, your armeture will over heat and draw more current, thus you loose the efficency of the design. Most common motors are either pre-wired and designed to run 3-phase, low-voltage 208, or high-voltage 480. 380V is a European rating, which actually is at 50Hz instead of 60Hz.

Now comes the next device in the system, are you going to use a VFD to control the start up and to maintain the load for efficiency? The VFD control is the next best thing to drinking water in conserving energy on a large scale plan.

Maximo

"Most common power designs for industrial / commercial buildings is 3-phase, 120/208; 120/480; 277/480."

Only in North America. He never said he was in N. America.

You wrote: "Why do you have 380 V a/c?"

This is the voltage his utility company delivers. this is why.

As to the rest of your reply, I can only conclude that you are a carpenter maybe?

Wangito.

is it ok

OK-- but YOU CAN NOT GET more than 1 HP continuously.

Your motor will operate at a slower speed, but will be OK

Your motor will operate at a slower speed, but will be OK

That would be the case if it was a universal motor or a brushed DC motor but the one being described here is a synchronous AC type which means a lower voltage will result in less current which causes a reduction in torque.

It is simple when you use regulator for the ceiling fan actually what happens? Regulator reduced voltage and in turn reduces the speed of fan. Similarly for this induction motor RPM will reduce, it will draw more current to sustain for RPM and efficiency of motor will be laser than the projected one.

"It is simple when you use regulator for the ceiling fan actually what happens? Regulator reduced voltage and in turn reduces the speed of fan. Similarly for this induction motor RPM will reduce, it will draw more current to sustain for RPM and efficiency of motor will be laser than the projected one."

Also, re: "Your motor will operate at a slower speed, but will be OK"

People, please. If you do not know what you are talking about, please refrain from responding. You are comparing small household Shaded Pole motors that you experience in appliances such as cooling fans to an industrial rated 3 phase motor (as anything rated for 460V would be). They are NOT built the same and cannot be controlled the same way. Do not supply erroneous information like this, it can lead to someone doing something that causes a fire!

my friend , it's better for the meantime to use 380v power supply and connect the motor winding STAR ( WHY) configuration , but as they said befor , you will not get effeciency 100% of course .

And here I remind you not to connect DELTA configuration , if so you will damage the motor windings ( it will be over heated ).

Here I preffer to follow Mr Meve/123 advise and buy a step up transformer ( this solution if you really need 1.5 HP motor not less ).

thanks

If it is a 460V motor, it is a NEMA design so there would be no ability to reconnect in Star as you would an IEC motor.

Possibly over heat and prematurely fail.

De-rate the motor by 50% or think of your motor as being a 3HP.Take another 15% safety margin for CCS (continues commercial service) RPM will stay the same, if not overloaded under the new parameters. If these are met, it will work fine through the life expectancy of the motor.

Wangito.

Dear Mr.ustrux,

Similar topics appeared several times.

Pl. refer the link below and you find your answer.

http://cr4.globalspec.com/search/sitesearch?do=show&srchobjs=t%2Cc&order=asc&fs=12&sort=textmatchrank&srch=460%20V%2060%20HZ%20WITH%20380%20V%2050hz

DHAYANANDHAN.S