CHAPTER 15 APPENDIXES

(9) Calculating the regenerative power

Regenerative operation is caused while the torque value is negative, in general as indicated below.

Horizontal feed: During deceleration

Vertical feed: During constant speed feed in the lowering cycle and during deceleration

Regenerative energy during deceleration (E1)

E1[J] = (2π/60) × TDC[Nm] × N[r/min] × tDC × (1/2)

Regenerative power during constant speed feed (E2) ←Mainly in lowering cycle

E2[J] = (2π/60) × TL[Nm] × N[r/min] × tL

TDC : Deceleration torque [Nm]

Accumulated energy on main circuit capacitor (E3)

E3[J] = (1/2) × C[F] × V2

= (1/2) × C[F] × {3902 - (200√2)2 }

TL : Load torque [Nm]

tDC : Deceleration time [s]

tL : Constant speed time [s]

tcyc : Cycle time [s]

Regenerative power (P)

P[W] = { | (E1 + E2) | - E3} / (tcyc)

P≤0: No external regenerative resistor is necessary.

P>0: The external (internal) regenerative resistor is

necessary.

C : Servo amplifier capacitor capacity [F]

→See page 15-29.

V2 : Regenerative transistor ON level2

- (200√2)2

= 3902 - (200√2)2

Calculate the average regenerative power (P) of each cycle of the operation pattern1 to check if P

is within the regenerative resistor capacity. If it is not, an external regenerative resistor is

necessary.

(10) Reviewing the operation pattern and mechanical configuration

If Trms exceeds TR, review the following items.

 Increase the acceleration/deceleration time a little in the allowable range.

 Reduce the operation frequency (increase the cycle time).

 If the rotation speed allows, increase the reduction ratio.

 Increase the motor capacity.

 If the stopping time of a hoisting machine is too long, adopt a mechanical brake.

 In case of operation at a high frequency, increase the reduction ratio and reduce the inertia.

15

Capacity Selection Calculation 15-23