science

Load dump

Load dump is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Load dump rather than just read about it. In short: Load dump means the disconnection of a powered load. It can cause two problems: failure of supply to equipment or customers large voltage spikes from the inductive generator(s) In automotive electronics, it refers to the disconnection of the vehicle battery from the alternator while the battery is being charged.

Key takeaways

Load dump belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Load dump to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Load dump from memory before moving on to harder problems.

Reference excerpt

Load dump means the disconnection of a powered load. It can cause two problems:

failure of supply to equipment or customers large voltage spikes from the inductive generator(s) In automotive electronics, it refers to the disconnection of the vehicle battery from the alternator while the battery is being charged. Due to such a disconnection of the battery, other loads connected to the alternator experience a surge in the voltage on the battery bus. This surge may be as high as 120 volts and the surge may take up to 400 ms to decay. It is typically clamped to 40 V in 12 V vehicles and about 60 V in 24 V systems.

Overview The field winding of an alternator has a large inductance. When the vehicle battery is being charged, the alternator generates a large current, the magnitude of which is controlled by the current in the field winding. If the battery becomes disconnected while it is being charged the load on the alternator suddenly decreases. However, the vehicle's voltage regulator cannot quickly cause the field current to decrease sufficiently, so the alternator continues to generate a large current. This large current causes the voltage on the vehicle bus to increase significantly—well above the normal and regulated level. All the loads connected to the alternator see this high voltage spike. The strength of the spike depends on many factors including the speed at which the alternator is rotating and the current which was being supplied to the battery before it was disconnected. These spike may peak at as high as 120 V and may take up to 400 ms to decay. This kind of a spike would damage many semiconductor devices, e.g. ECUs, that may be connected to the alternator. Special protection devices, such as TVS diodes, varistors which can withstand and absorb the energy of these spikes may be added to protect such semiconductor devices. Various automotive standards such as ISO 7637-2 and SAE J1113-11 specify a standard shape of the load dump pulse against which automotive electronic components may be designed. There can also be a smaller inductive spike due to the inductance of the stator windings. That may have a larger voltage, but it will be for a much shorter duration, as relatively little energy is stored in the inductance of these windings. Load dump can be more damaging because the alternator continues to generate power until the field current can decrease, so much more energy can be released.

References

Worked examples

Example 1 — a first encounter with Load dump

Start with the simplest possible case. Write down what Load dump claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Load dump before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Load dump ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Load dump

In research: Load dump appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Load dump in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Load dump is common in secondary-school and first-year university syllabi. It links to neighbouring topics Power electronics, so understanding it makes those chapters shorter.
In everyday life: Look for Load dump outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Load dump in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Load dump means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Load dump out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Load dump in simple terms?

Load dump means the disconnection of a powered load. It can cause two problems: failure of supply to equipment or customers large voltage spikes from the inductive generator(s) In automotive electronics, it refers to the disconnection of the vehicle battery from the alternator while the battery is…

Why does Load dump matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Load dump?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Load dump.