The specifications for the motor power and encoder cables fabricated by GE Fanuc and shown in Table 3-13 are shown below. Although the motor power cables can tolerate moderate flexing they are not designed to withstand continuous flexing as in cable track applications. The encoder cables are not recommended for flexing applications.
Wiring The Optional Motor Brake
The following figure shows a typical wiring example for the optional S-Series and MTR-Series servo motor holding brake. The brake must be energized using a 24 VDC power supply to release its hold on the motor. Chapter 2 contains motor brake specifications showing the current requirements for each model motor. GE Fanuc offers a 24 VDC, 5 amp DIN-rail mounted power supply (Part Number IC690PWR024) that may be used. If the brake control contact is rated for switching the inductive load of the Motor Brake Coil, the control relay (CR1) may not be required.
Regenerative Discharge Resistor Selection and Wiring
Regenerative energy is normally created in applications with a high load inertia, high speed, vertical axes and/or frequent acceleration and deceleration. When decelerating a load, the stored kinetic energy of the load creates generator action in the motor causing energy to be returned to the servo controller. For light loads and low acceleration rates, the controller may be able to absorb and store this energy in the DC link filter capacitors or dissipate it in an internal regenerative resistor. Otherwise, an optional external regenerative discharge unit must be installed.
The S2K Series controllers include an internal regenerative discharge resistor that will control the regenerative energy in most applications. When an Over Voltage fault (LED Status Code OV) or an Excessive Clamp Duty Cycle fault (LED Status Code EC) occurs during motor deceleration, the cause is usually excessive regeneration and requires an optional external regenerative resistor kit. The SSI104 controller has no provisions for connecting an external resistor. As an alternative to adding an external resistor you can try a combination of the following actions:
• Reduce the deceleration rate and/or increase deceleration time
• Lower the top speed of the motor
• Reduce machine cycle rate
• Reduce load inertia connected to the motor
• Increase vertical axis counterbalance
GE Fanuc offers several different resistor kits (all kits include resistor mounting brackets) as shown in Table 3-23. Wiring between the resistor and the controller’s power terminals is not included in the kit and is the user’s responsibility. Connections to the resistor can be made by soldering, using a faston type terminal of appropriate size, or using a ring terminal bolted through the hole in the resistor terminal tab. See Figure 3-49.
Caution
Under normal operation the regenerative discharge resistor may become very hot. To prevent being burned, never touch the resistor. Mount the resistor well away from heat sensitive components or wiring to prevent damage. Also, the terminals of this resistor are at a high voltage potential. Either insulate the connections or provide adequate shielding to eliminate this shock hazard.
The resistor values included with the kits are average values for a variety of conditions. Smaller capacity (wattage) resistors may work in some applications and larger resistors may be required in others. The lower the resistance value, the faster the regenerative energy can be dissipated. Applications with large inertial loads, high speeds, and high deceleration rates regenerate more energy and may require a resistor with a lower resistance and/or larger capacity (wattage). As an alternative, when the capacity or resistance of the standard external regenerative resistor is insufficient for the application, reducing load inertia, maximum speed, deceleration rate, increasing vertical axis counterbalance or some combination of these measures can decrease the regenerative energy. See Section 3.8.1 for details on selecting the proper resistor based on application requirements.
The wiring between the controller and the regenerative resistor should be kept as short as possible (less than 20 inches or 50cm) to prevent possible damage to the switching transistor from voltage transients due to cable inductance. The regenerative resistor may become very hot during normal operation. Therefore, route all wiring away from the resistor so that the wiring does not touch the resistor and has a minimum clearance of 3 inches (76mm).
Connect one terminal of the resistor to the controller’s “EXT” power terminal and the other resistor terminal to the “DC+” controller power terminal. See 3.6.10 Connection Diagrams.
Note:If you are not using an external resistor, a wire jumper must be connected between the power terminals “INT” and “EXT” as shown in the “Clamp ConnectionsExternal” sections of 3.6.10. If this jumper is not installed, the internal resistor is disabled and the controller may exhibit symptoms associated with excessive regeneration. This note does not apply to the SSI104 model controller.
When mounting the resistor, tighten the lock nut sufficiently to compress the lock washer. Although the lock nut should be tightened securely, avoid over-tightening so as not to strip the bolt threads.
Calculating Regenerative Power and Selecting a Resistor
Use the following calculation to determine the average regenerative power that will be released in your application. These calculations ignore any losses due to resistance in the motor armature and lead wire. Based on the calculations, select the appropriate regeneration resistor kit from Table 3-23. The continuous power rating of the selected resistor must exceed the average calculated regenerative power from the equation below:
STEP 5: Selecting a Regenerative Discharge Resistor Kit
If an external regenerative resistor kit is required it must meet the following criteria:
1. The resistance of the selected resistor must exceed the Minimum External Resistance value shown in Table 3-243-24 for your specific controller.
2. The value calculated for the Average Regenerative Power must be less than the Continuous Power rating shown in Table 3-23 for the selected resistor kit.
Contact GE Fanuc if you require assistance in selecting the appropriate value.
STEP 6: Determine the Peak Power Requirements for the Resistor
The peak power determines the maximum rate at which the regenerated energy must be dissipated to prevent overvoltage faults on the controller. The peak power must be calculated for each deceleration period of the profile by dividing the regenerated energy for that period by the time over which the energy is released.
Peak Power = Regenerated Energy/ Regeneration Time
This value must be lower than the Peak Power rating for the resistor selected (see Table 3-23). If a non-standard resistor is substituted, its peak power can be calculated as follows:
230 VAC Models Peak Power = 4102 / R Watts
460 VAC Models Peak Power = 8252 / R Watts
where R is the resistance value in ohms for the selected resistor.
Regeneration Application Example:
Assume a vertical axis using an SLM100 motor (Jm = 0.001491 lb-in-s2 ) with a load inertia (JL) of 0.0139 lb-in-s2 . The SLM100 motor uses an SSI107 controller. The friction torque in the axis (Tf) is 10 in-lb and the torque that is required to support the load against gravity (Th) is 15 in-lb. The axis requires the following compound velocity profile:
Since the example machine cycle involves a number of periods where regeneration occurs, the determination of the regenerated energy is more complicated. Regeneration occurs for each deceleration period when the axis is moving in the upward direction (against gravity) and during the period when the axis is moving in the downward direction. These areas are shaded in the profile shown above. The regeneration for each of these periods must be calculated as follows:
STEP 1a: Calculate the rotational energy during period t1:
Ed1 = (6.19×10-4) x (0.001491+0.0139) x (20002 – 10002 )= 28.58 Joules
STEP 1b: Calculate the rotational energy during period t2:
Ed2 = (6.19×10-4) x (0.001491+0.0139) x (10002 – 02 ) = 9.53 Joules
STEP 2a: Calculate the energy absorbed by friction during period t1:
Ef1 = (5.91×10-3) x 0.2 sec x (2000 RPM-1000 RPM) x 10 in-lb = 11.82 Joules
STEP 2b: Calculate the energy absorbed by friction during period t2:
Ef2 = (5.91×10-3) x 0.2 sec x 1000 RPM x 10 in-lb = 11.82 Joules
STEP 3: Calculate the regenerative energy for downward motion during period t3:
Ev = (1.182×10-2) x 15 in-lb x 2000 RPM x 1 Sec = 354.6 Joules
STEP 4: Calculate the Average Regenerative Energy for the entire cycle (Eavg):
Eavg = 28.58 + 9.53 – 11.28 – 11.82 + 354.6 = 369.1 Joules
To determine if the SSI107 controller can absorb this amount of energy, first determine the net energy the regeneration resistors must dissipate. To find this Net Energy value, subtract the energy stored in the controllers bus filter capacitors as shown under the Capacitor Energy Storage heading in Table 3- 24.
Net Energy = 369.1 Joules – 41.1 Joules = 328 Joules
Next, we must convert this Net Energy to power so we can compare the result with the dissipation capability of the controller’s internal regeneration resistor.
Average Power = Net Energy / Total Cycle Time = 328 / 2 Sec = 164 Watts
We now compare this result to the controller’s Max. Continuous Power rating from Table 3-24. Since the 164 Watts required is more than the 25 watts allowed by the SSI107 controller, an external regenerative resistor is required.
STEP 5: Determine the proper external regeneration resistor size:
If we refer to the resistor selection criteria shown in Step 5 above, we must first select a resistor that has a resistance value larger than the Min. External Resistance for the SSI107 controller shown in Table 3-24. Therefore, our resistor must be at least 50 Ω. From the second criteria our calculated value of 164 Watts for the Average Regenerative Power must be less than the Continuous Power rating of the resistor we select.
From Table 3-23 we see that resistor kit IC800SLR002 has a resistance of 100Ω and a continuous power rating of 225 Watts which meets both of the selection criteria.
STEP 6: Check the peak power (Ppk) requirements for each regeneration period:
For period t1: Ppk1 = 28.58 Joules / 0.2 seconds = 142.9 Watts
For period t2: Ppk2 = 9.53 Joules / 0.2 seconds = 47.65 Watts
For period t3: Ppk3 = 369.1 Joules / 1 second = 369.1 Watts
The largest of these values, 369.1 Watts, is still less than the 2880 Watt Peak Power rating of the IC800SLR001 resistor kit so this standard resistor can be used.
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VMIVME-5565
VMIVME-5565–010000
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VMIVME-7740-840
VMIVME-4150
VMIVME-5576
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VMIVME-7698–140
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VMIVME-4140–000
VMIVME-7750
VMIVME-7698–140
VMIVME-2540–300
VMIVME-4140–000
VMIVME-3215–000
VMIVME-2533-000
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