Triacs Turn off time - can it be faster?
This is normal for a Motor drive with low load.

The low Power Factor is due to the motor inductance when little "work" is being done.  Under load the current phase shifts towards the voltage the "real" component of energy [W] vs the "Stored" phase shifted " component of energy [VAR]

Meanwhile this reactive energy or  excitation current in the motor core also creates back EMF to reduce the current in the windings ( inductive impedance increases with speed) but a current  lags almost 90 deg when running with no load.  

Since the Triac shuts off near zero current ( I_hold threshold) this explains why you get what you see. 

This only problem you may see with the transition power during switching with V*I across triac can cause self-heating during start surge currents of 800 % and abrupt speed changes.

I hope I am explainin' in terms you understand.

Try a current shunt or CT and view V,I(t) or V vs I in XY or product of V*I for a better understanding about losses in Triac.


  For a 1st order under approximation, I measure DCR of motor coil and lookup triac ESR by Vdrop @ rated Current and compare.  If ESR of Triac / DCR motor > 2% , I would expect a heat sink is needed and if >10% the Triac may be undersized.  This is because conduction losses are proportional to R  (I^2*R)