Quick answer. This category holds one product, EM-0001, a DC machine with a loading arrangement - and the loading arrangement is the reason it is worth having. An unloaded machine can only be run; a loaded machine yields characteristics. Speed against load, torque against current, efficiency, and the differences between shunt, series and compound connection all require a controllable load and a way to measure what it is taking. Two things have to be settled before an order, and both are commonly missed: are the field windings brought out so the machine can be connected shunt, series and compound, and is a starter supplied - because a DC motor must not be switched directly onto its supply. Both are explained below.
Every result a DC machines syllabus asks for is a relationship between two quantities as the load changes. With no load there is one operating point and nothing to plot. So the loading arrangement decides what the machine can teach, and the options are not equivalent:
| Loading method | What it gives you | What to watch |
|---|---|---|
| Rope or band brake on a drum | Simple, visible and cheap; torque from a spring balance reading and the drum radius, which students can see is a direct measurement | All the energy becomes heat in the brake - it needs cooling and it smells; the reading drifts as the drum warms, and the brake wears |
| A second machine as a generator into a resistive load bank | The most useful arrangement for a teaching laboratory. Smooth, repeatable, electrically measurable loading - and the second machine can itself be studied as a generator, so one set supports both halves of the syllabus | Needs the second machine, a coupling and a load bank; the load bank gets hot and needs ventilation |
| Eddy current brake | Precise, settable, no mechanical wear, and easy to hold at a fixed value while readings are taken | Needs its own supply and cooling, and it cannot hold load down to zero speed |
| Back-to-back or regenerative arrangement | Full-load testing while drawing only the losses from the supply - the professional method | Two matched machines and more complex control; more than most teaching laboratories need |
Our recommendation for a teaching laboratory: the machine-plus-generator-and-load-bank arrangement. It is clean, it is repeatable between groups, the loading is measurable in electrical units students are already recording, and the set does double duty as a generator experiment. A brake drum is a good second arrangement precisely because the torque measurement is visibly mechanical.
The three connections give three completely different machines, and the comparison between them is the core of the subject:
So the question to put on the enquiry is simple and decisive: are the shunt and series field windings brought out to separate terminals so that all three connections can be made by the student? A machine with its connections made internally gives one characteristic and no comparison. Ask also for a field rheostat, because field control is one of the two speed control methods the syllabus requires.
There are two routes to an efficiency figure, and the honest comparison between them is one of the most valuable things this experiment teaches.
Swinburne's test is a no-load test. The machine is run light, the no-load losses are measured, the resistances are measured, and the efficiency at any load is then calculated. It is quick, it needs no loading equipment and no large supply, and it is the only practical method for a large machine in a small laboratory.
What it cannot tell you, and this is the part worth teaching:
So: run both, and compare them. The two figures will differ, the students will want to know why, and the answer is the list above. That single comparison teaches more about engineering measurement than either test alone.
1. A DC motor is never switched directly onto its supply. At rest the armature generates no back electromotive force, so the only thing limiting the current is the armature resistance, which is small - and the inrush is many times the rated current. It blows fuses, it stresses the commutator and it can damage the windings. The answer is a starter: a resistance in series with the armature, cut out progressively as the machine accelerates and the back electromotive force builds. Confirm that a starter is supplied with the machine, and that it is the correct type. A three-point or four-point starter also carries the protective features in the next paragraph, which is why it matters more than it looks.
2. Never open the field circuit of a shunt motor while it is running. This is the serious one. Losing the field means losing the flux, and with little flux the machine accelerates to try to generate back electromotive force - a lightly loaded machine will run away to a destructive and dangerous speed. The practical provisions: a no-volt and field-failure release in the starter, a field rheostat that cannot be turned to open circuit, and a standing instruction that the field circuit is never disconnected or its rheostat taken to maximum while the armature is energised. Put it on the wall by the machine, not only in the manual.
Beyond those two: the coupling and any exposed shaft need a guard, the set needs bolting down, an emergency stop must be within reach, loose clothing and long hair kept clear, and the load bank or brake treated as hot.
Tell us which of these the laboratory already owns and we will quote the gap. A machine delivered without a starter, a load and a means of measuring torque cannot run a single experiment on the syllabus, and that is the commonest way this purchase disappoints.
Related ranges: electrical engineering trainers and electrical training equipment for the wider machines, drives and control range, power electronics lab trainers for thyristor speed control of these machines, and power instrumentation lab for the measurement side. The full training kits and electronics lab trainer kits categories list the rest.
Because at rest it generates no back electromotive force, so the armature current is limited only by the armature resistance - which is small, giving an inrush many times the rated current. It blows fuses, stresses the commutator and can damage windings. A starter inserts resistance in series with the armature and cuts it out progressively as the machine speeds up and the back electromotive force rises. Confirm the starter is supplied and is the correct type for the machine.
The machine loses its flux and accelerates, because it needs speed to generate back electromotive force against the supply - and a lightly loaded machine can run away to a destructive speed. It is the classic DC machine hazard. The protections are a field-failure release in the starter, a field rheostat that cannot reach open circuit, and a standing instruction that the field is never disconnected while the armature is energised.
Both, and the comparison is the lesson. Swinburne's test is quick, needs no loading equipment and gives a calculated efficiency at any load. It cannot show temperature rise, commutation behaviour under heavy current or the effects of armature reaction, and it assumes the loss model is correct. Run both on the same machine, compare the figures, and let the students work out why they differ.
For most teaching laboratories, a second machine run as a generator into a resistive load bank: the loading is smooth and repeatable, it is measured in electrical units the students are already recording, and the generator can itself be studied. A brake drum is a good complement because the torque measurement is visibly mechanical. An eddy current brake is precise and needs its own supply and cooling.
Only if the field windings are brought out to separate terminals so the student can make each connection. Many machines have the connections made internally, which gives one characteristic and removes the comparison that is the point of the experiment. Ask explicitly, and ask for a suitably rated field rheostat at the same time.
Because it was created around a single item, and we would rather say so than pad the page out. The wider range of machines, drives and control equipment is in the categories linked above, and we have recommended that this record be merged into them. Send us your machines syllabus and we will quote across all of them in one reply.
Ray Export is a manufacturer and exporter of laboratory, scientific and educational equipment based at Plot No. 449, HSIIDC Industrial Area, Saha, Ambala, Haryana 133104, India. Enquiries: [email protected], +91-9817319615.
Written by Palak Mall, Senior Content Writer. Technically reviewed by Arvind Kumar, Lab Equipment Specialist, 12+ years in laboratory and testing instrumentation. Last updated: 17 October 2026.
This page is deliberately short because the category holds one record; padding it would serve nobody, and specifications for a single product belong on its own page. Notes published rather than hidden: the product name carries the padding phrase "For Vocational Training And Didactic...", which we are removing, and a category of one product named "Electric Motors" understates and misdescribes what is in it - we have recommended it be merged with our electrical machines ranges. The machine behaviour, test methods and safety rules above are general electrical engineering practice rather than claims about a particular model. Ratings, supplied accessories, starter type and all other specifications will be confirmed in writing on the quotation; verify them before tender submission, and confirm electrical safety requirements with your own institution and national rules.
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