Regeneration unit select guidance

Transcription

1 Regeneration unit select guidance

2 Definition of resistor A resistor is a two-terminal electronic component having a resistance (R) that produces a voltage (V) across its terminals that is proportional to the electric current (I) flowing through it in accordance with Ohm's law: V = IR Within rated temperature, voltage and current, resistor is linear. However, when the voltage or current is beyond rated value, the resistor will be overheated to dismatch Ohm s law. Sometimes it will be even burnt. When selecting a resistor, we need to take a closer look at its specification and features about its rated current, voltage. Classification of resistors There are many kinds of resistors with different structures and different way to classify. There are carbon film resistors, metal film resistors, winding resistors, metal oxide film resistors, SQP and pellet resistors. You could check the features of different resistors as attached. Rule of resistor: The current through resistors in series stays the same, but the voltage across each resistor can be different. The sum of the potential differences (voltage) is equal to the total voltage. To find their total resistance: Resistors in a parallel configuration each have the same potential difference (voltage). To find their total equivalent resistance (R eq ):

3 Regeneration unit Regeneration unit of servo systems takes advantage of its resistance features to transform and absorb electrical power. Due to its special working conditions, there are some special requirements about regeneration units. Now big power level regeneration units are normally classified as RSLG and RXHG. These two kinds of resistors could be capable of high temperature endurance, continuously being loaded by big power and big current to meet the demand of servo systems. Wire wound resistors are commonly made by winding a metal wire, usually nichrome, around a ceramic, plastic, or fiberglass core. The ends of the wire are soldered or welded to two caps or rings, attached to the ends of the core. The assembly is protected with a layer of paint, molded plastic, or an enamel coating baked at high temperature. Wire wound resistor Aluminum resistor is composed of spring alloy and shaped alumina coat. After high temperature, special noninflammable heatproof cement is filled and then dried in the shade, finally processed to be fixed and insulated. Because the whole resistor is filled with heatproof cement, no external mechanical force or dusty environment will affect. It is big power level, hard, anti-vibration, well heat dissipated, low resistance/temperature ratio, linear and easily installed resistor.

4 Principle of regeneration Regeneration happens when motor decelerates. At this moment, motor could be considered as a generator. Regeneration could absorb the energy of a rotating load and transform this energy into electrical power that is finally reverted back to the servo drive. The major job of regeneration is to consume the inertia power of load in the movement and transfer the power to the capacitor to dissipate. When EDB servo system is undertaking the maximum load inertia at rated speed, EDB must absorb all the energy generated when the load stops to prevent its system from being damaged. If the system operates above rated speed or maximum load, external regeneration is necessary. Regeneration relies on 3 factors: Torque, deceleration speed and movement cycle. Sometimes, in some special applications the power of C1 or R1 is not big enough and an external resistor or capacitor will be necessary. The aim of regeneration: EDC servo drive: Capacitor is used for internal regeneration. If external regeneration is required, we need to connect external regeneration unit to terminal P and N. If in one system there are a lot of similar servo drives, all the P terminals could be connected together and all the N terminals could be connected together, which could add the regeneration power. This is just like connecting all C1 together but it relies on a complete analysis of system operating cycle. EDB servo drive: There are internal resistor R1 and capacitor C1. If any external regeneration is required, we will have to remove the internal R1 and connect a resistor between terminal B1 and terminal B2. Regeneration process: Normally, the power supply to one servo system is 200v. A normal P-N bus voltage is 283v( ). When a servo motor begins to decelerate, the energy feedback to the servo drive begin to increase the P-N voltage. Some or all the energy is used to charge C1. However, when the voltage surpasses 380vDC, regeneration transistor TR1 will be activated. Then, the energy will be consumed by

5 resistor R1. Hence, the transistor will be switched cyclic between 380VDC and 370VDC. Deceleration with load will need several cycle. When the power couldn t be consumed completely, A13, overvoltage alarm could happen and bus voltage is above 420VDC then. Sometimes A16 (regeneration error) could happen, which means TR1 has been switched on for too long time. (There is a internal register to record TR1 s on/off time. Regeneration sequence: If A13 and A16 happen, we need to change the resistance of R1. We need to consume more current through the resistor. According to V=I*R, we could increase the current by using a smaller resistor. Increasing the power of the resistor is not the only solution because the current through R1 is still the same. After changing the resistor, we need to recheck. Once we reduce R1, the current through R1 increases. If the current increase too much, it may exceed the rated power of the resistor so we will need to increase the power of the resistor. The calculation of regeneration: If the regeneration power is beyond the rated power of internal resistor, we need to add an extra resistor. As what we see in equations, the energy generated when motor stops, load, capacitor C1, motor wiring and resistor R1 should be considered. Energy generated by motor: En=0.5JM[(2πN/60)2] Energy consumed by capacitor: Ec=0.5C(Vk2-Vr2) Energy consumed by the winding of motor. Em= 3[JMN(2πIr/60Tr)]2*(Ra/td) Energy consumed by load EL=0.5TL(2πNtd/60) Because the sum of all kinds of energy should be 0, we could calculate the energy that the resistor needs to consume: Er=En-Ec-Em-EL Hence we could calculate the power of regeneration resistor: Wr=Er/Cycle

6 Negative load If one load forces servo motor to rotate, this kind of load is called negative load. In this situation, continuous regeneration happens to the servo drive. We should avoid the motor s output torque to be different from the motor s actual rotation direction. Application of negative load:

7 Load descends without a counter weight motor used in conveyor belt Regeneration resistor selection guidance Please refer to the form as below to choose a suitable resistor. Suitable Servo Drive EDB series Pronet series Specification of internal resistor Resistance(Ω) Capacity(W) Mininum allowable resistance(ω) EDB EDB EDB EDB EDB EDB Pronet Pronet Pronet Pronet Pronet Pronet-75D Pronet-1AD Pronet-1ED Notice: When we add external regeneration resistors, we will need to remove internal regeneration resistors at first. Before ordering, please add -x after the model ( For example, EDB-08AMA-x), in which regeneration resistor is not included.

8 Name Carbon resistor (RT) Metal film register(rj) Addendum: normal resistor list Wire wound Metal oxide resistor(rx) film(ry) Cement resistor Sheet resistor (RL) Integrated circuit(b-yw) Apperance