Questions tagged [ratings]

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1answer
49 views

Understanding relay contact ratings

The "ice cube" relay in question is allen bradley's 700-HC series. I was browsing through the spec sheet looking at the electrical data to make sure that the relay has the proper voltage/current ...
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3answers
47 views

How is a transistor power calculated

I refer to a 2N3055 power transistor, the spec. sheet gives the following: Max. current 15A, Max. Voltage 50V, Power rating is 115 Watts. What is the power rating calculated on? If it is E*I ...
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1answer
399 views

Is C0G a synonym for NP0?

This question is in the context of a production environment where part numbers and change notices are strictly controlled, and any alternate manufacturer parts under an internal part number must be ...
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2answers
94 views

If a capacitor has a low voltage rating, why isn't it damaged by low current, high voltage static charge?

Capacitors usually have a voltage rating marked on them. From what I gather, it's the maximum voltage it can withstand without being damaged. Let's assume you have a 35V capacitor and you rub your ...
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2answers
57 views

Modifying a buck converter for lower current rating

I have been learning about buck converters and I think I understand the principle of their design. However, I am unsure of how a current rating would be calculated for a particular design. The ...
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2answers
417 views

Difference between [W] and [WS] power rating of resistors

I see some datasheets of power resistors where power ratings are in Watts [W] and some in [WS] which I don't know what they mean. What is the difference between them? Example of datasheet Some ...
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3answers
2k views

Does the wattage of a resistor factor into the resistance of a resistor?

Resistors come in a variety of different ratings based on wattage. As a rule, lower wattage resistors are smaller than higher wattage resistors. I understand the wattage determines roughly how much ...
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1answer
35 views

replacing obsolete HEMT and differences between Package/Case and Supplier Device Package

I've been designing an amplifier, with ATF33143 as my HEMT in mind. Yet, I just found out the said HEMT went obsolete. So I started looking at SKY65050-372LF as a possible replacement. On the DigiKey ...
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1answer
42 views

How to spec out a relay correctly

I have a load that I am trying to switch with a relay. The load to the relay is an autotransformer. The wiper output of the autotransformer is (2) 120:30 step down transformers with each having 150W ...
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1answer
50 views

Connector current/thermal rating

This question started as a design specific question but is (now) more of a general question going forward onto other PCB product designs... For now, I am designing an I/O PCB and want to mix supply ...
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1answer
489 views

Difference between Rated Load & Max. Switching Voltage on Relay Contacts

Under the 'contact ratings' of a relay datasheet, there is a row for rated load, which specifies a 10A 30VDC load on both NO and NC contacts. There is another row which is the max. switching voltage ...
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2answers
74 views

Electromagnetic switch

I have a a electromagnetic level switch with DPDT contacts. Its rating mentioned is 230Vac, 60VA, 1A. My concern is what will be the DC equivalent for this rating. I have 24Vdc available from PLC and ...
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1answer
115 views

Why are there two different output voltage ratings on some power supplies? and How it works? [closed]

some power supplies (ex. chargers) have two different output voltage ratings like: 5V 2A OR 9V 2A -why is that? -How the charger knows that my load needs 5V or 9V? and not damaging the load -...
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1answer
127 views

resistor power rating [closed]

After 100 mSec, switch (SW) is going to bypass the resistor permanently. what should be the wattage of resistor? In image voltage source is of 700V, R=7ohm, L=330micro Henry, C=1.36mF.
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1answer
343 views

Switch Current Rating - Current Maximum

I've searched through a lot of threads regarding this and found some answers, however, the data sheet I am provided has some information which is causing some confusion. I have a switch with the ...
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1answer
129 views

Apple AirPods watt hour meaning [closed]

I have a part of Apple's product information sheet and I was wondering if I can make an assumption : I am wondering if I can say : "hmm, if the Wh rating of AirPods Charging Case is 1.52Wh, then a 5V ...
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1answer
105 views

Whats the relation between AC power strip current rating and DC output current from the PSU connected on

this is kind of a noob question: I have a power strip (extension cord from my wall AC outlet) that is rated for 250V 10A. Over this power strip i'm connecting a power supply that gives an output of ...
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1answer
72 views

Is meaning of rated voltage not always same?

Well, I'm stuck in choosing DC barrel jack which will supply power for my circuit board from 12V 1.5A AC/DC adapter. Its spec says voltage rating is 18V and current rating is 1.5A. Well.. I know that ...
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3answers
12k views

How can I test battery for true mAh rating?

Is there a way I can test the capacity of a 3.7v rechargable lion battery like this at home? All I really have is a multimeter. (Image source)
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1answer
71 views

contradictory resistor ratings [duplicate]

A lot of resistors, like This one, are rated both for breakdown voltage and for maximum power. Well, this is probably a stupid question, but if a 10MOhm resistor is rated for 10kV, 1Watt, certainly at ...
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2answers
375 views

Power Mosfet Gate Voltage

The early Power Mosfets were deemed to be fully enhanced with 10 VDC between gate and source. The gate source threshold voltage was defined for 1mA drain current and would be between 2 and 4 VDC. The ...
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2answers
921 views

Verifying supercapacitor capacity

I have procured some supercaps. No datasheet was provided. The only data I have is what is printed on the caps themselves: "4.0F 5.5V cda®" Since my DMMs don't ...
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1answer
1k views

Will a 0.5V difference in output damage the device? [duplicate]

I have a speaker adapter, with an output rating of AC 11.5V ~ 1600mA, which I am looking to replace and the only replacement I can find has a rated output of 12V ~ 2000mA. I've read somewhere that a ...
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1answer
135 views

Can I use a fuse rated 400V 32A on a 220V 32A circuit? [closed]

Can I use a fuse rated 400V 32A on a 220V 32A circuit?
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2answers
469 views

Peak Voltage Ratings of SMD Inductors

Off the shelf SMD Ferrite coils are widely available and popular .The power ratings are adequate for many applications.The manufacturers are clear about the current ratings for saturation and copper ...
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1answer
84 views

Help with resistor rating

I'm having a problem with finding out the value of resistor that has 5 band color code but matches 4 band color code. I'm presuming its 0.47 5%, but I could be wrong. Resistor is blown and there is ...
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2answers
2k views

What is the meaning of collector current pulse in the datasheet?

Here is the datasheet of a transistor: http://www.adafruit.com/datasheets/TIP120.pdf In maximum ratings, there is a section called "Collector Current (Pulse)". What does that mean in practice? Lets ...
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1answer
57 views

SSR selection - how is on resistance related to output IV curve?

I am looking at the datasheet at the link below, and I can't for the life of me figure out what I am missing. http://www.digikey.ca/product-detail/en/TLP3542(F)/TLP3542F-ND/871299 This is a Toshiba ...
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2answers
737 views

Why are some common-mode chokes rated in ohms instead of henries?

Some common-mode chokes, including this one, are rated in ohms instead of in henries. Why? Isn't the impedance injected by the common-mode choke entirely frequency dependent? Is there an assumed ...
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1answer
136 views

How will I get the per-unit parameters when the data from the short-circuit test are shady?

Data from short-circuit and open-circuit tests of a 60-Hz, 100-kVA, 4600–230-V transformer are: VOC = 230 V IOC = 14 A POC = 60 W VSC = 172.3 V ISC = 20.2 A PSC = 1046 W Get (a) ...
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1answer
843 views

Stepper motor current specifications - 12V/350mA, but draws more at lower speeds?

I have on hand a simple 12V/350mA stepper motor the datasheet is lacking, so I can only assume 12V is the maximum sustained voltage and 350mA is again, the maximum associated current. The datasheet ...
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2answers
3k views

What does a parenthesized current rating on a switch mean?

I'm speccing out some switches for a project... is this some standard notation I've never seen before? Electrical Ratings: 12(4)A 250V AC What does the ...
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1answer
66 views

How would I properly develop a current rating for this system…?

I have a system that I have recently developed for in house (manufacturing) equipment testing. Transformers rated for 80VA (264V, .303A) are used in series and rectified using a full-wave diode bridge....
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2answers
998 views

Transformer Rating Selection

For selecting a transformer, I stumbled across the following equations for obtaining VA and IAC (citation here). I am dealing with a full wave bridge rectifier with a capacitive load. The wiki ...
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3answers
454 views

Diode Drop vs Open Drain Output Tolerance

I have an LED Driver IC that states a 5.5V tolerant Open Drain Output. It's Absolute Maximum section indicates 6.5V with a note saying "The input negative-voltage and output voltage ratings may be ...
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1answer
1k views

Minimum voltage input for thermoelectric unit

Context: I am trying to make a drink cooler with a thermoelectric unit (peltier unit). I want to supply the minimum amount of energy as possible to the peltier unit. Now on my peltier unit, it says "...
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1answer
201 views

What is the minimum voltage for general loads and peltier units

I am confused with "power ratings" on devices and electrical components. First, what is the power rating on a home appliance or a electrical component saying when it is 12V? Is it saying "we would ...
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3answers
5k views

Magnetic reed switch current ratings

I wish to use some 12 V, 5 W xenon light bulbs under separate shelves of a cabinet. I'd like them to power-on using a magnetic reed switch attached to the cabinet door. The magnetic reed switch I ...
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1answer
253 views

Interpretation of rating of the primary voltage of a real transformer [duplicate]

The rating of a real transformer is 15 kVA , 2300/230-V then can we say that the primary rms is 2300 V or can we say that the secondary rms is 230 V or both. To clarify further, suppose to solve for ...
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3answers
26k views

Voltage rating vs. power rating of a resistor

My question may sound very basic, but I am very confused by the difference between the voltage and power ratings of a resistor. Vishay's document says: Rated Power The maximum amount of power ...
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1answer
967 views

Is a 115V rated transformer expected to accept US mains voltage (120V)?

< question completely reworded since people thought I was looking for appliance repair instructions > Many "Power Transformers" are rated at 115V or 230V. It seems to be the most popular rating. ...
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3answers
687 views

Why do they place a high current device in a low current package?

For instance, it is said that the practical current limit of the TO-220 device is 75A. But I frequently see MOSFET devices for which the specified maximum continuous drain current is above 75A. (...
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2answers
2k views

Get motor ratings from unknown DC motors

I've purchased bulk cheap DC motors for a robot problem. But I don't know their ratings. Is there a way for me to find out? For instance, I would like to know their max DC voltage input using basic ...
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1answer
155 views

How should I read the voltage ratings on this terminal strip?

http://www.farnell.com/datasheets/63479.pdf I don't understand the voltage ratings given. On the far left, it looks like four different voltage ratings. Is there some way to tell which ones are ...
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4answers
1k views

Why can't a power supply supply low current?

I've just read this article and don't quite understand how a power supply can't supply such a low current. I was always under the impression a power supply could supply anything up to its rating, but ...
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3answers
2k views

Vacuum cleaner power rating does not match line voltage and current rating

I have a vacuum cleaner on which is proudly written: 12.0 Amps 1300 W Assuming a 120 V (RMS) power supply, how would the power consumption of the vacuum cleaner be calculated given the 12.0 A ...
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1answer
541 views

ULN2003A rating

I am confused about what this statement means: Each channel rated at 500 mA and can withstand peak currents of 600 mA. Does it mean that the ULN is capable of driving up to 500 mA per channel ...
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2answers
584 views

LCD rated at max 5.5 V used at 6V

I'm trying to use an LCD (DEM16101) from a uC. At some point I've connected it's power input to a 6V battery (above its 5.5 V max rating). I can't initialize it properly so at this point I'm ...
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2answers
30k views

Selecting the right bridge rectifier

There are a number of schematics I'm trying to interpret that have bridge rectifiers. In the components list, however, they're simply listed as "D1-D4 rectifier unit" without any specific values. How ...
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1answer
1k views

Relay contact voltage rating

I was looking through to buy a few relays and found the nominal DC contact voltages (~30v) are much smaller than the nominal AC contact voltages (250v). What is the reason for such a large difference? ...