External Shunt Option [-SX1]
The -SX1 option provides a connection for a user-provided shunt resistor to dissipate excess energy and keep the internal drive voltage within safe levels. The drive switches this resistor "ON" when the internal bus voltage reaches approximately 380 VDC. This option is generally required for systems that have a large amount of stored mechanical energy that must be dissipated during deceleration.
DANGER: Shock and Fire Hazard
Electrical wiring must be designed and installed in accordance with local electrical safety regulations to prevent the risk of fire and electrical shock.
The shunt resistor dissipates a high quantity of power. To prevent the danger of electric shock or fire, you must obey the precautions that follow:
- Correctly size, mount, and protect the external shunt resistor.
- Do not touch the shunt resistor terminals. There are lethal voltages on the terminals.
- Do not touch the surface of the drive or the external shunt resistor. The temperature can exceed 70°C.
- Restrict access to the shunt resistor while it is connected to a power source.
Table 2-55: -SX1 Component Information
|
Component |
Description |
Aerotech P/N |
|---|---|---|
|
Recommended Shunt Resistor |
50 Ω (min), 300 W Vishay/Dale: RBEF030050R00KFBVT |
ECR01039 |
|
1-Pin Mating Connector [QTY. 2] |
Screw Torque Value: 0.6 - 0.8 N·m Wire Size: 0.2 - 6 mm2 [24-10 AWG] Phoenix: 0708250 |
ECK02452 |
|
F101 Fuse on the Control Board |
8 A S.B. | EIF01022 |
|
Recommended Wire Size |
16 AWG (1.3 mm2) High Temperature |
-- |
Equation 1:
Calculate the kinetic energy of the system. Any energy that is not lost to the system could be regenerated to the DC bus.
| EM | = [1/2][JM + JL]ꞷ2M | ; rotary motors |
| EM | = [1/2][MM + ML]v2M | ; linear motors |
| Where: | ||
|
JM |
= rotor inertia (kg·m2) | |
|
JL |
= load inertia (kg·m2) | |
|
ꞷM |
= motor speed before deceleration (rad/s) | |
|
MM |
= forcer mass (kg) | |
|
ML |
= load mass (kg) | |
|
vM |
= velocity (m/s) | |
Equation 2:
You will need a shunt resistor if the regenerated energy is greater than the Maximum Additional Storage Energy that the internal bus capacitor can store ( Maximum Additional Storage Energy for a Standard iXC4/XC4).
| ECa | = (1/2)· C · (V2M - V2NOM) | |
| Where: | ||
|
C |
= bus capacitor (F) [ |
|
|
VM |
= turn on voltage for shunt circuit (V) [ |
|
|
VNOM |
= nominal bus voltage (V) [ |
|
Table 2-56: Maximum Additional Storage Energy for a Standard iXC4/XC4
|
Bus Voltage |
Maximum Additional Energy |
|---|---|
|
160 V |
71.3 J |
|
320 V |
25.2 J |
If a shunt resistor is required, calculate the value of resistance necessary to dissipate the energy.
Equations 3, 4, and 5:
Calculate the parameters of the shunt resistor.
Equation 3:
| PPEAK | = (EM - ECa) / tD | |
| Where: | ||
|
PPEAK |
= peak power the regeneration circuit must accommodate (W) | |
|
tD |
= deceleration time (s) | |
Equation 4:
| PAV | = (EM - ECa) / tCYCLE | |
| Where: | ||
|
PAV |
= average power dissipated on shunt resistor (W) | |
|
tCYCLE |
= time between deceleration events (s) | |
Equation 5:
| R | = (2VM - VHYS)2 / 4PPEAK | |
| Where: | ||
|
VHYS |
= hysteresis voltage of regeneration circuit (V) [ |
|
Additional useful equations:
| 1 lb·ft | = 1.356 N·m | |
| 1 rad/s | = 9.55 rpm | |