As an HVAC technician, you will be dealing primarily with inductive loads; motors, compressors, transformers, relays, and contractors. This article will help you understand inductance and the effect it has on electrical circuits.
Inductance:
Most of us have had the pleasure of using a wheelbarrow. When it is loaded, it takes quite a bit of work and effort to start the wheelbarrow moving (opposing change). But, once you have it moving it takes a lot less work to keep it moving (no opposition). In fact, it is much easier to keep the wheelbarrow moving than it is to stop the wheelbarrow (opposing change), which again takes quite of bit of work. Inductance has the same effect on current in an electrical circuit. It requires more energy to start the current flowing than it does to maintain the current flow.
All circuits have some measure of inductance, even a straight piece of wire. However, it is the inductive loads (in particular motors) that have wire windings where inductance has its greatest effect on the circuit. When current begins to flow (changing) through a coil of wire, a magnetic field is induced, this magnetic field creates a counter electromagnetic force (EMF) that opposes current flow. Once the current has reached its peak and is maintained, the counter EMF is no longer present until there is another change of current. In an inductive circuit, voltage leads current. In a previous article, you can read how this has a great effect on motors in an HVAC circuit.
In a circuit that has AC voltage and current, the change of current is continuous so inductance has a greater effect on the circuit than it would on a DC circuit. In HVAC work there is little need to measure inductance but you do need to be aware of it and its effect on an electrical circuit.
In our next HVAC training article, we will explore inductance further to see how transformers, relays, solenoids, and contractors work using inductance.
Do you want to become an HVAC technician and jump-start your HVAC career? Sign up for our HVAC Technician course.
by Ron Walker
Inductance:
The property of an electric circuit that opposes any change of the existing current.Given the above definition, it stands to reason that the effect inductance has on a circuit is only present when there is a change in current. Here is an everyday example to help explain inductance:
Most of us have had the pleasure of using a wheelbarrow. When it is loaded, it takes quite a bit of work and effort to start the wheelbarrow moving (opposing change). But, once you have it moving it takes a lot less work to keep it moving (no opposition). In fact, it is much easier to keep the wheelbarrow moving than it is to stop the wheelbarrow (opposing change), which again takes quite of bit of work. Inductance has the same effect on current in an electrical circuit. It requires more energy to start the current flowing than it does to maintain the current flow.
All circuits have some measure of inductance, even a straight piece of wire. However, it is the inductive loads (in particular motors) that have wire windings where inductance has its greatest effect on the circuit. When current begins to flow (changing) through a coil of wire, a magnetic field is induced, this magnetic field creates a counter electromagnetic force (EMF) that opposes current flow. Once the current has reached its peak and is maintained, the counter EMF is no longer present until there is another change of current. In an inductive circuit, voltage leads current. In a previous article, you can read how this has a great effect on motors in an HVAC circuit.
In a circuit that has AC voltage and current, the change of current is continuous so inductance has a greater effect on the circuit than it would on a DC circuit. In HVAC work there is little need to measure inductance but you do need to be aware of it and its effect on an electrical circuit.
In our next HVAC training article, we will explore inductance further to see how transformers, relays, solenoids, and contractors work using inductance.
Do you want to become an HVAC technician and jump-start your HVAC career? Sign up for our HVAC Technician course.
by Ron Walker