Schneider Electric 17S Series manual Determining Optional External Regen Resistor Size, Power

Determining Optional External Regen Resistor Size

Power	The following is the procedure for calculating the power dissipated by the Regen
Dissipation	resistor in a simple system wherein friction is negligible. Ignoring friction in the
Calculation	following calculations gives worst case results since friction will absorb a portion of
Procedure	the energy during deceleration. An example of each step in this procedure is
	provided later in this chapter.
	Step	Action
	1	Plot speed versus time and torque versus time for the entire move cycle.
		(Magnitude of the torque is not required; only the direction is required.)
	2	Identify each section of the plot where the drive is decelerating the load or
		where speed and torque have opposite signs.
	3	Calculate the energy returned to the drive in each deceleration using the
		formula E = ½ J t ω2
		Where
		E = Energy in joules
		Jt = Total system inertia, including motor, in kg(m2)
		ω = Speed at start of deceleration in radians per second
		(ω = 2 π RPM / 60)
	4	Compare the energy in each deceleration with the energy required to turn
		on the Regen circuit. (See Drive Energy Absorption Capability table.) If the
		energy is less than that listed in the table, disregard that deceleration for
		the remainder of the calculations.
	5	Calculate the energy dissipated by the Regen resistor by subtracting the
		energy listed in the table from the energy of the deceleration.
		E	= E	– E
		dissipated	generated	absorbed by capacitors
	6	Calculate the pulse power of each deceleration by dividing the dissipated
		energy by the time of the deceleration.
		Ppulse = Edissipated / Tdecel (seconds)
	7	Calculate the continuous power dissipated by the Regen resistor by
		totaling all the dissipated energy and dividing it by the total cycle time.
		Pcontinuous = (E1dissipated + E2dissipated+… +En dissipated) / Ttotal cycle (seconds)
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