# How can I apply a load to an electric motor to simulate realistic conditions for an experiment?

I am trying to perform some experiments with a motor and I want to run it under realistic conditions (or at least not unloaded). Is there an easy way to load a motor?

A couple ideas I had include: attach water paddles to paddle water continuously, attach pulley to lift weight, clamping brake pads (getting desperate), ...

I am working with a 1/3 HP three-phase motor.

• What type of load will it be driving under 'realistic conditions'? Aug 12 '15 at 19:52
• Brake pads are not too bad an idea as a general concept. The classic dynamometer is to have a pulley or drum with a friction outer surface, lap a band with one end captive around half the drum and apply a force to the bands "free end" with a spring or similar - usually with a tension spring balance or digital equivalent in series. Force on band end x drum radius gives torque x RPM gives power. Adjust tension to vary load. At 1/3 HP ~+ 250 Watts it should be possible to arrange material for drum and band that will dissipate the power. .... Aug 13 '15 at 11:45
• .... A car drum brake would find this load level trivial - you can determine how much power it is liable to be abe to handle from vehicle stopping rate at appropriate speed. Aug 13 '15 at 11:45
• @ChrisMueller I don't have anything specific in mind. For more background, I am interested in running experiments on the motor and see how it changes the current draw. I'm sampling the current pretty fast so I'm looking for changes in the spectrum among other things. Aug 13 '15 at 18:12

You could couple the motor to an electric generator equipped with braking resistors. This is how dynos driven by test vehicles are slowed down.

Attach a flat paddle across the axle that moves against the air.

(image source: woodgears.ca)

• From a safety perspective if this type of arrangement were to be followed it would be better to have the motor more securely attached to a base. Also to prevent injuries from the paddle flying off, either the paddle or the whole device needs to be enclosed by a protective guard. If I was conducting the experiment I would also be wearing safety glasses. With every test I would also be rechecking the security of the paddle; I wouldn't want to be hit in the face or have my eye gouged out by a flying object.
– Fred
Aug 13 '15 at 0:32

You could use almost anything as a load. As has been mentioned before, a brake would work, so would a second motor, driven as a generator with a bank of power resistors as a load (They can get nice and toasty). A variable pitch propeller in air would work, varying the pitch would change the load. So would a centrifugal pump circulating a fluid, if you had a flow control valve opening and closing it would vary the load. The possibilities are pretty much wide open.

Personally, I think the easiest to implement would be using a second motor and a resistor bank, but that's mostly because that's what I did way back when I was in college.