I’ve written articles regularly about the differences between hydraulics and electrics, but today I’d like to write about what is not different. To be honest, more is similar with the two forms of energy than is different, especially from a physical perspective. If you are an expert in either industry, you already know more about the other than you realize.
Both hydraulics and electrics involve quantities of energy being transmitted to achieve work. The hydraulic method of achieving work is to apply force to an actuator, which in turn moves a load. The electric method of achieving work is to apply force to an actuator, which in turn moves a load.
I use the word actuator to describe any device which converts one form of energy into mechanical energy. In the case of hydraulics, these actuators are hydraulic cylinders and hydraulic motors. In the case of electrics, these actuators are linear motors and electric motors. The electric linear motor uses electro-magnets to glide a load to and fro, but I see no reason that an “electric cylinder” can’t be manufactured with a neodymium piston and wire-coil barrel (if this hasn’t been invented yet, please e-mail me for instructions on where to send the royalty checks when you steal my idea).
What allows any physical object to move is force. Force must be applied to create motion, and I can think of no exception to this rule. Force in hydraulics is created by pressure, and force in electrics is created by voltage. The application of hydraulic force (i.e., pressure) and electric force (voltage) doesn’t matter, because they are essentially the same.
Pressure is the intensity or magnitude of hydraulic energy. The higher that intensity, the more potential there is to do work. Electrical engineers will notice I used the word “potential,” just as is used in the electrical kingdom. Voltage is also a measure of electrical intensity or magnitude, and represents the potential to do work.
The word potential is used because it doesn’t matter how high the magnitude, if the opposing force has the same magnitude, no work can be achieved. What really matters is the difference between the force going into the equation and the resistance to that force. For example, if you are putting 5000 psi into a hydraulic motor creating 100 lb-ft of torque, but your load is resisting with 10,000 lb-ft of torque, raising the pressure to 10,000 psi does nothing but give us a paltry 200 lb-ft. However, if the load were just 25 lb-ft, our potential is more than enough to create work. The same principle applies to voltage; the higher the voltage, the harder the electrons are trying to push, and the lower the downstream voltage, the higher the potential.
I hope it’s clear that voltage and pressure are similar principles, and they can even be controlled in similar fashion with voltage/pressure regulators. But the similarities do not stop there. The other component of power is the factor of time. When converting energy, it’s just as useful to push twice as fast as it is to push twice as hard. For hydraulics, the time component of power is flow (e.g. gallons per minute) and with electrics the time component of power is amperes (e.g. coulombs per second).
Essentially, flow and amps are the rate in which you’re creating force through pressure or voltage. Flow is the volume of fluid molecules moving past a single point, and amperage is the number of charge carrying electrons moving past a single point, in both cases, over a specified period of time. Power in either example is the combined factors of either pressure and flow, or voltage and amperage. Both even use the same equation:
Horsepower = pressure│voltage x flow│amps ÷ constant
The similarities of electrics and hydraulics don’t end at the physical principles, and in one of the next blogs, I’ll discuss the functional similarities of the two.