Dc Motor Machines Lab Equipment Manufacturer, Supplier and Exporter in India

DC and AC Machines for Electrical Labs

The framework: specify the load, not just the machine

A motor on a bench with nothing attached to its shaft can demonstrate that it turns. Everything else on an electrical machines syllabus needs a load that can be set, held and measured. There are four ways to do it and they teach different things at different prices.

Ask how torque is measured, and insist the geometry be stated. A spring-balance-and-drum arrangement needs the drum diameter; a torque arm needs its effective length and the balance or load cell calibration. These are not details of the apparatus - they are numbers the student multiplies, and a missing one turns a measurement into an estimate.

The baseplate and the coupling decide the machine's working life

This is the specification that costs nothing to ask about and a great deal to retrofit. A motor-generator set is two machines that must run concentric and parallel within a tolerance. Misaligned, they destroy bearings and couplings, make noise, and transmit vibration into the bench.

• Ask whether the set is supplied on a common machined baseplate, pre-aligned, with a flexible coupling and a coupling guard - or as two loose machines. Loose machines mean your workshop builds the bed and does the alignment, which is real work and real risk.
• Ask for the coupling type and guard. An exposed coupling between two machines in a room full of students is not acceptable; a guard that has to be removed to see the shaft will be left off.
• Ask about the feet, the mounting and the floor or bench loading, and whether the set is intended to be bolted down.
• Ask what is done about the shaft extension for a tachometer or a brake drum, and whether it is keyed.

Starters and protection are part of the experiment, not accessories

• A DC motor must not be started direct-on-line. At rest there is no back-EMF, so the armature current is limited only by armature resistance and is destructive. A three-point or four-point starter with its starting resistance is therefore both a safety device and a teaching object - the reason it exists is a question worth asking students. Confirm which starter is supplied with each DC machine, and that its rating matches.
• Induction motors need a starter matched to the rating and the supply. Direct-on-line is acceptable for small machines; star-delta is the standard teaching arrangement for larger ones and is itself an experiment. Confirm which is supplied and whether the motor is wound for star-delta starting with all six terminals brought out - because a motor with only three terminals cannot do that experiment at all.
• Overload and earth-leakage protection, and a reachable isolator. Ask what protection is fitted, and make sure each bench has an isolator the student can reach from the reading position rather than one behind the machine.
• Terminals brought out to a marked terminal block. The whole point of a teaching machine is that students make the connections: field and armature separately for a DC machine, all six stator ends for an induction machine, rotor terminals for a wound-rotor machine. Confirm the terminal arrangement and that it is clearly and durably marked.

The supply is half the purchase

A DC machine needs a DC supply, and almost no modern building has one. That means a rectifier unit or a DC drive, sized for the armature and with a separate adjustable field supply - because the classic experiments depend on varying field and armature independently. This is the single most common omission in a machines-laboratory order, and it is discovered on commissioning day.

• Ask explicitly what DC source is included or assumed, with its voltage, current and whether the field supply is separately adjustable.
• For AC machines, confirm three-phase availability at the bench, the voltage, and whether a variable supply is needed. A variable AC supply is required for several standard tests, and an autotransformer of adequate rating is a separate item - see variac electrical lab equipment.
• Ask about inrush. A room of machines started at the same moment by a class is a different load from one machine, and the lab's distribution board has to cope. Worth raising with your electrical contractor before the machines arrive.

Instrumentation: the ranges matter more than the count

• Wattmeter ranges. A lightly loaded induction motor runs at low power factor, and a wattmeter chosen for full-load power reads a small, uncertain deflection at the light-load end of the curve - which is exactly where the curve is interesting. Ask for the ranges, and for switchable ranges where possible.
• Three-phase power by the two-wattmeter method is a standard exercise, and it needs two wattmeters with the correct connection and an understanding of why one may read negative. Confirm the instruments and the terminal access support it.
• Speed measurement. Ask whether a tachometer is included and whether it is contact or optical. An optical or non-contact tachometer is safer around couplings and does not load the shaft; a contact tachometer needs a shaft centre to bear on.
• Slip measurement on an induction machine is often done stroboscopically or by counting rotor slots; confirm what method the manual uses and that the equipment for it is supplied.

A note on the pole-changing machine

One record in this listing is a three-phase squirrel-cage induction motor of the Dahlander type. That is a genuine specification rather than a model name: the stator winding is arranged so that reconnecting the terminals changes the number of poles, giving two synchronous speeds in a 2:1 ratio from a single winding. It is a useful teaching machine precisely because the speed change is visible in the terminal connections rather than hidden in a drive, and it needs a switching arrangement to match. Confirm the two speeds, the connection diagram and whether the changeover switch is supplied.

What a quotation must state

• Each machine: type, rating, voltage, speed, insulation class, enclosure, and the terminals brought out.
• The loading arrangement, and how torque is measured, with the drum diameter or torque arm length stated.
• Baseplate, alignment, coupling type and coupling guard - supplied or not.
• Starters for each machine, with ratings, and the protection fitted.
• The DC supply - voltage, current, and whether the field supply is separately adjustable - and the AC supply and variable supply requirements.
• Instruments with their ranges, not merely their presence; tachometer type.
• Resistor or load bank rating, switching and ventilation, where one is used.
• Weight, footprint, floor loading, and whether the set is to be bolted down.
• Documentation: connection diagrams, the experiment set, and worked sample results so a technician can verify the set on arrival.

About this listing

The category is called "DC Motor Machines" and most of it is not DC. Across its five listing pages, only the first four records are DC machines - shunt, series, compound and a DC dynamometer. From the fifth record onward the listing is AC: single-phase induction, AC repulsion, a universal motor, three-phase wound-rotor slipring, three-phase synchronous and the pole-changing squirrel-cage machine described above. That is a good electrical machines range; it is simply not what the category name promises, and a buyer looking for AC machines will not search here.

Two smaller defects we have flagged for correction:

• Three spellings of one suffix inside the first ten records - "For Electrical Lab", "For Electrical Labs" and "for Electrical Lab" - appended to names that are otherwise clear. It repeats the category's own context and adds nothing a buyer searches for.
• One garbled name. One record reads "Universal Motor For AC Repulsion Motor For Electrical Lab". A universal motor and an AC repulsion motor are two different machines, and the name appears to be two records' text run together. If you need either, ask and we will confirm which machine is being quoted.

So enquire by experiment list. Send us the experiments on your syllabus, the class and batch size, and your supply situation - three-phase availability, whether any DC source exists, and the bench or floor space - and we will quote the machines, the loading arrangement, the starters, the supply and the instruments as one set, with ratings and geometry confirmed in writing. We have recommended internally that the category be renamed to cover AC and DC machines, the suffixes stripped, and the garbled record corrected.

Related ranges

Parent category: motor machines. Also electrical engineering trainers, power and instrumentation lab equipment, power electronics trainers for drives and converters, testing and measuring lab trainers for the instruments, electric motors, variac electrical lab equipment and electrical training equipment. The full electronics lab category lists the rest.

Frequently asked questions

Why is the loading arrangement more important than the machine?

Because every characteristic on the syllabus is obtained by varying a load and measuring it. A motor with nothing on its shaft can only demonstrate rotation. The load has to be settable, holdable and measurable, which is why the choice between a rope brake, a generator into a resistor bank, an eddy-current brake and machine-to-machine coupling changes what the laboratory can teach - and why the loading arrangement is the part most often left off an order.

Why must the brake drum diameter be stated on the quotation?

Because it is a term in the student's calculation, not a detail of the apparatus: torque comes from the spring-balance readings and the drum radius. The same applies to a torque arm, where the effective length and the balance or load cell calibration are needed. If the geometry is not stated, the measurement becomes an estimate - and the same principle applies to a brake drum as to a compressor receiver or an engine air box.

Why can a DC motor not be started direct-on-line?

Because at rest there is no back-EMF, so armature current is limited only by the armature resistance and reaches a destructive value. A three-point or four-point starter inserts resistance that is progressively cut out as the machine runs up. That makes the starter both a safety device and a teaching object - the reason it exists is a good question to put to students - so confirm which starter is supplied with each DC machine and that its rating matches.

What is most often forgotten when ordering a DC machines laboratory?

The DC supply. Almost no modern building has one, so a rectifier unit or DC drive is needed, sized for the armature and with a separately adjustable field supply - because the classic experiments depend on varying field and armature independently. Ask explicitly what DC source is included or assumed, with its voltage and current, rather than discovering the gap on commissioning day.

Does a motor need all six stator terminals brought out?

For star-delta starting and for several standard tests, yes. An induction motor with only three terminals brought out physically cannot do the star-delta experiment, however it is described. The same logic applies throughout: field and armature separately on a DC machine, rotor terminals on a wound-rotor machine. Confirm the terminal arrangement and that it is clearly and durably marked, since students make the connections.

Is this really a DC machines category?

No - only the first four records are DC. The rest of the five pages are AC machines: single-phase induction, AC repulsion, universal, three-phase wound-rotor slipring, three-phase synchronous and a pole-changing squirrel-cage machine. It is a good range under a name that does not describe it, which we have flagged for correction. Send us your experiment list and supply situation and we will quote across both.

Key takeaways

• Specify the load, not just the machine. The loading arrangement is the experiment and the usual omission from an order.
• Get the torque geometry on the quotation - brake drum diameter or torque arm length - because the student multiplies by it.
• Buy the set on a pre-aligned common baseplate with a coupling guard, or budget for your workshop to build and align the bed.
• Starters and protection are part of the experiment. Confirm the starter per machine, and all six stator terminals if star-delta is on the syllabus.
• The DC supply is half the purchase, with a separately adjustable field supply - and plan for class-wide inrush with your electrical contractor.
• Ask for wattmeter ranges, since the light-load end of an induction motor curve is where a full-load-ranged instrument fails you.

About this page

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 gives specification guidance and quotes no prices; prices depend on machine ratings, loading arrangement, supplies, instruments and destination, and are issued only as dated written quotations. Machine ratings, voltages, speeds, insulation classes, enclosures, terminal arrangements, baseplate and coupling provision, starter types and ratings, protection fitted, DC and AC supply requirements, instrument ranges, load bank ratings, weights and footprints will be confirmed in writing on the quotation before order. Electrical installation, distribution capacity, protection coordination and the inrush of a class starting machines together must be assessed by a qualified electrical engineer for your own building; nothing on this page substitutes for that assessment. Statements about starting, loading and measurement practice are general electrical machines practice rather than claims about any particular product. The record counts, the suffix variants and the garbled record name described above were read from this listing on 16 October 2026 and will change as it is corrected.