Hi Pat:
Your message said that you have a switching-mode power supply
in parallel with a resistive load. The resistive load has a
5-minute on and off cycle.
When the resistive load is on, the product complies with the
harmonic current limit requirements. When the resistive load
is off, the product does not comply with the harmonic current
limits.
That's what I would have predicted. And, you've got the proper
test set-up.
The standard does have some consideration for very short term
situations where the construction might exceed the standard.
But, the situation you describe doesn't fit the exceptions.
Some designers have seriously considered putting light bulbs
in parallel with the switching-mode power supply just to get
around the harmonic current limit requirements. You might want
to consider installing some light bulbs to switch into the
circuit when the heater is off.
Or, get a PFC-corrected power supply.
Best regards,
Rich
ps: My personal opinion is that the mains is to serve us,
the consumer. We don't have to correct for linear
non-unity power factor loads, why do we have to correct
for non-linear non-unity power factor loads?
