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3
votes
1answer
430 views

Short circuit in welding

All I know about welding is it is a technique in which electrode is connected to one terminal and the gripper connected to workpiece is in connection with the other terminal. As current passes and ...
2
votes
2answers
34 views

Why is the Current to Motor less than Motor Rated Current?

I have a motor for a submersible pump with a Rated Current of 8.4A as given in the motor's electrical data. However, when it is running, I record a current of 3.4-3.9A. Is there a fault I am supposed ...
0
votes
0answers
16 views

How to preferentially enhance the changes in conductivity in fabric materials

I want to realise a fabric pressure sensor and I have these 2 materials available: a highly conductive fabric with surface resistance approximately 30 Ω; a piezoresisitive conductive fabric with ...
0
votes
1answer
30 views

Steel surface welding with high-frequency current

High-frequency currents induce skin-effect resistance that is used on some applications to weld metals. Assume you have two steel rectangles of dimension $h_0, w, l$ and $h_1, w, l$ placed together ...
3
votes
1answer
153 views

Stall Torque of a DC Motor Less than Theoretical Values

I have an unknown DC motor with specifications I was testing. I used a Prony Brake setup and scale to evaluate torque, a tachometer for RPM, and multimeters for voltage and current. I get a linear ...
0
votes
0answers
46 views

Stiffness control of DC motor using PWM

Is it possible to control the output torque of a brushed DC motor using PWM? From my understanding the speed is directly proportional to voltage applied and torque is proportional to current drawn. ...
-5
votes
1answer
84 views

In the equation for power as a function of current and resistance, what do the two factors for current represent?

In the electric power equation $P=RI^2$, $P$ represents the product of $RII$. I'm trying to understand the fundamental anatomy of the $RII$ term. More precisely, why does the current, $I$ appear ...
5
votes
1answer
1k views

In the Apollo 13 mission, how could the batteries have “no Volts” with two Amps of current?

In the movie Apollo 13 there's a scene when the LEM is losing power; when they switch the module on, one of the astronauts reads the levels and says that one battery has no Volts but 2 Amps. What did ...
1
vote
1answer
47 views

Will AC Motor Maintain Speed of Descending Object

Suppose we have an AC motor which needs to lower an object at a set speed. We use a PID loop to determine and correct positional errors. Presumably the PID loop will keep the current low as most of ...
4
votes
1answer
276 views

How does conductivity $\sigma$ of salt-water depend on salinity?

In what way does the electrical conductivity $\sigma$ (or conversely, resistivity $\rho = 1/\sigma$) depend on the salinity $S$ of the saline- (or sea-) water? I know they must be in some way ...
2
votes
1answer
98 views

What materials or techniques can I use to reduce this electrical effect when building spotwelding tables?

I have been experimenting with building various support tables around press-type spot-welders. These are relatively simple fixures; think of a tabletop with legs under it and devices like sliding ...