HITACHI INVERTER SJ/L100/300 SERIES PID CONTROL USERS’ GUIDE After reading this manual, keep it for future reference Hitachi America, Ltd.
CONTENTS 1. OVERVIEW 3 2. PID CONTROL ON SJ100/L100 INVERTERS 3 2-1 PID Control (1) P : Proportional Control (2) I : Integral Control (3) D : Differential Control (4) PID Control 3 4 5 5 5 2-2 PID Gain Adjustments & Control Characteristics 6 3.
1. OVERVIEW SJ100/L100 series inverters have an integrated PID control function as standard. They can be used for controls, such as constant flow control for fan & pump applications, and they have the following features. l Target signal can be given not only by the digital operator but also by an external digital signal, which can be set to 16 different targets. Furthermore, it can also be given by an analog input signal (0 - 10V or 4 20mA).
SJ100/L100 series inverters have integrated PID control, which is indicated by the dotted line in Fig. 2-1. You can use PID control by setting a target value and providing a feedback signal. The example in Fig. 2-2 shows a connection diagram for ventilation flow control in a fan application. SJ100/ Target L100 Feedback (DC0-10V, 4-20mA) Transducer 4 bit of digital Flow volume sensor input signal Fan Motor Fig.
(2) I: Integral Control This is a control to correct the output frequency by integrating the deviation. In the case of proportional adjustment, a large deviation will result in a large output frequency adjustment, but if the deviation is small, then the resulting adjustment of output frequency will also be small. However, you cannot make the deviation zero. Integral performance compensates this problem.
2-2 PID Gain Adjustments & Control Characteristics The optimal gain factors of PID vary from condition to condition, and from system to system. That means it is necessary to set those parameters by taking into account the individual control characteristics of your particular system.
3. HOW TO USE 3-1 Structure & Parameters (1) Control Mode Integrated operator A71 : 00 / 01 DOP, DRW F43 : PID SW ON / OFF SJ100/L100 series inverters feature the following two control modes: l Frequency control mode l PID control mode These can be selected by “PID function selection (A71)”.
(3) Deviation Calculation Every calculation in PID control in the SJ100/L100 is based on “%” so that it can be used with various applications and units of measure, such as pressure (N/m2), flow (m3/min), temperature (degrees) and so on. For example, comparing target value and feedback value is based on % of target and % of feedback full scale value. However, there is a useful function called scale conversion function (A75).
100 100 100 75 % 25 75 % % 25 0 0 0 0 0 2V 4mA 20% (a) A13 = 20% A14 = 100% A11 = 25% A12 = 100% 10V 20mA 100% 0 0 0 0 5V 10mA 50% (b) A13 = 0% A14 = 50% A11 = 0% A12 = 75% 10V 20mA 100% 0 0 0 2.5V 7.5V 10V 5mA 15mA 20mA 25% 75% 100% (c) A13 = 25% A14 = 75% A11 = 25% A12 = 75% Fig. 3-3 Setting Active Range : Example 2 As you can see from Fig 3-3, if you set parameters A11 and A12 other than “0”, you should set the target value inside the valid range of the vertical axis.
3-2 Summary of Parameters for PID Control On the SJ100/L100 series inverters, the same function numbers are used for both frequency control mode and PID control mode. The function name for each function is based on frequency control mode, which is normally used for general application. Therefore, some functions have misleading explanations in the instruction manual. To avoid confusion, please find in below Table 3-1 the explanation of function names for frequency control mode and PID control mode.
3-3 Example of Set Up (1) Parameter Set Up under Frequency Control Mode Before driving the system in PID mode, you set up each required parameter under frequency control mode. Pay particular attention to the following items. l Acceleration ramp and Deceleration ramp The output of the PID calculation (refer to Fig. 3-1) will not immediately be an output frequency of the inverter.
(3) Scale Conversion Factor Setting Set this factor according to your application, e.g. flow, pressure, temperature and so on. For a detailed explanation, please refer to item (6) on page 9. (4) Target Input by Digital Input Signal Please refer to the following when changing the target with the digital input signal (4 bit max.). (a) Input terminal assignment L100 series inverters have five intelligent input terminals. The SJ100 series have six.
3-4 Example of Each Gain Adjustment (Kp & Ti) l Check the response of feedback signal or the output frequency of the inverter when making a step change in the target. (Please refer to Fig. 2-4) l Use an oscilloscope or other measuring equipment to observe the waveform of the feedback value or output frequency of the inverter (frequency monitor). l Prepare two targets that can be changed by digital input signal in advance, so that you can change targets with a step change.
4. EXAMPLE OF ACTUAL APPLICATION You can find in this chapter some typical setting examples for actual applications. 4-1 Constant Flow Control L100/ SJ100 Feedback Target Transducer 4 - 20mA (500m3/min when 20mA) 4 bit digital signal Flow sensor Pump Flow : 150m3/min or 300m3/min constant Motor Fig. 4-1 Example of Constant Flow Control % 500m3/min 100 In this case (targets are 150m3/min & 300m3/min), the settings would be as follows: 300m3/min 150m3/min 60 30 0 10.
4-2 Constant Temperature Control In the case of constant flow control shown in the previous section, output frequency of the inverter increases if the feedback value is smaller than target value, and output frequency of the inverter decreases if the feedback value is bigger than the target value. However, in the case of constant temperature control, this is the opposite.
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