what is the best and cheapest load to test a variable frequency drive (1 HP VFD) at full load?
Maybe a centrifugal pump ?
Thanks in advance
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\$\begingroup\$ The best test is in the intended worst case condition or a simulated load, which can be constant I, constant R, constant P and a pulsed load with a high crest current factor like a pump which may have a crest factor of 5 , more or less. A product Validation test confirms the performance test with OEM test methods and some margin test with temperature rise of hotspots and all feedback & safety sensors. \$\endgroup\$– Tony Stewart EE75Sep 15, 2017 at 1:13
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\$\begingroup\$ For example one could use a PWM full bridge to regulate a load with the heat dumped into a load rated for 5x the load eg. 4kW heater and then use PWM to use a % of this load with some pattern and some much higher f commutation rate. Halogen bulbs tend to have high crest factor to some motors and with suitable instruments determine Load regulation and Load dump performance from a stored energy source. But if you can define BEST then a real answer is possible. \$\endgroup\$– Tony Stewart EE75Sep 15, 2017 at 1:22
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The cheapest and easiest test is to couple the VFD motor to a similar motor connected to mains power. Using the VFD motor to drive the mains-connected motor about 3% above synchronous speed will present full load to the VFD motor. That will provide a reasonable test over a range of loads from zero to at least 150% of rated load. The load is easily controlled by varying the speed between synchronous speed and about 5% above synchronous speed. This method provides no capability for testing the VFD at any operating frequency other than mains frequency and slightly above.
A centrifugal pump is a good test load, but the pump curve controls the load at any given speed.
The best test load ultimately depends on how thoroughly you want to test the VFD. A really thorough test requires a dynamometer.