Merge pull request #16 from upb-lea/develop

add area/volume LUT for balancing resistors

Author: gituser789

docs/wordlist

@@ -84,3 +84,6 @@ pllsi
 CKC
 CAS
 SMD
+ni
+pdf
+vishay

pecst/__init__.py

@@ -14,3 +14,6 @@
 from pecst.film import *
 from pecst.ceramic import *
 from pecst.electrolytic import *
+
+# resistor data (for balancing electrolytic capacitors)
+from pecst.resistor import *

pecst/constants.py

@@ -36,6 +36,7 @@
 ELECTROLYTIC_CAPACITOR_DATA_DIRECTORY = "electrolytic_capacitor_data"
 ELECTROLYTIC_CAPACITOR_DOWNLOAD_DIRECTORY = "electrolytic_downloads"
 CERAMIC_CAPACITOR_DOWNLOAD_DIRECTORY = "ceramic_downloads"
+RESISTORS_DATA_DIRECTORY = "resistor_data"
 
 # film capacitor settings
 FILM_CAPACITOR_SERIES_NAME_LIST = ["B3271*P", "B3272*AGT", "B3277*P"]
@@ -47,6 +48,11 @@
 ELECTROLYTIC_DEFAULT_TOLERANCE_PERCENT = CapacitanceTolerance.TwentyPercent
 ELECTROLYTIC_CAPACITOR_SERIES_VALUES = "series_values"
 
+# parallel resistor settings (for electrolytic capacitors)
+# from source https://www.vishay.com/docs/28730/ac_ac-at_ac-ni.pdf
+# currently only a single series is allowed!
+RESISTOR_SERIES_NAME = "ac"
+
 # SMD ceramic capacitor section
 SMD_SIZE_DICT = {"size": ["C0402", "C0603", "C0805", "C1206", "C1210", "C1808", "C1812", "C1825", "C2220", "C2225", "C3040", "CAN06", "CAN08", "CAN12",
                           "CAN13", "CAN17", "CAN18", "CAN19", "CAN21", "CAN22", "CKC18", "CKC21", "CKC33", "CAS21"],

pecst/electrolytic/selection.py

@@ -20,7 +20,9 @@
 from pecst.electrolytic.current_capability import parallel_electrolytic_capacitors_lifetime_current_capability
 from pecst.electrolytic.power_loss import power_loss_per_electrolytic_capacitor, calc_leakage_currents
 from pecst.electrolytic.capacitance_change import calc_capacitance_factor_frequency, calc_capacitance_factor_temperature
-from pecst.electrolytic.resistors import generate_resistor_list, calculate_r_parallel_max, look_for_closest_smaller_resistance, loss_per_resistor
+from pecst.resistor.resistors import (generate_resistor_list, calculate_r_parallel_max, look_for_closest_smaller_resistance, loss_per_resistor,
+                                      select_resistor_area_volume)
+from pecst.resistor.read_resistor_database import load_resistors
 
 logger = logging.getLogger(__name__)
 
@@ -205,10 +207,6 @@ def select_electrolytic_capacitors(c_requirements: CapacitorRequirements) -> tup
 
             logger.info(f"After in parallel sort-out: {c_db.head()=}")
 
-            # volume calculation
-            logger.debug("Volume calculation.")
-            c_db["volume_total"] = c_db["in_parallel_needed"] * c_db["in_series_needed"] * c_db["volume"]
-
             # loss calculation per capacitor
             logger.debug("Power loss estimation by ESR.")
 
@@ -239,8 +237,21 @@ def select_electrolytic_capacitors(c_requirements: CapacitorRequirements) -> tup
             c_db.loc[:, 'power_loss_total'] = c_db.loc[:, 'power_loss_per_capacitor'] * c_db["in_parallel_needed"] * c_db["in_series_needed"] + \
                 c_db["in_series_needed"] * c_db["loss_per_resistor"]
 
+            # load resistor database
+            r_df = load_resistors("ac")
+
+            # resistor volume calculation
+            c_db[["area_per_resistor", "volume_per_resistor"]] = c_db.apply(lambda x, r=r_df: select_resistor_area_volume(
+                x["loss_per_resistor"], c_requirements.temperature_ambient, r), axis=1)
+
             # calculate minimum required PCB area
-            c_db["area_total"] = c_db["area"] * c_db["in_parallel_needed"] * c_db["in_series_needed"]
+            c_db["area_total"] = c_db["area"] * c_db["in_parallel_needed"] * c_db["in_series_needed"] + \
+                c_db["in_series_needed"] * c_db["area_per_resistor"]
+
+            # volume calculation
+            logger.debug("Volume calculation.")
+            c_db["volume_total"] = c_db["in_parallel_needed"] * c_db["in_series_needed"] * c_db["volume"] + \
+                c_db["in_series_needed"] * c_db["volume_per_resistor"]
 
         if not os.path.exists(c_requirements.results_directory):
             os.makedirs(c_requirements.results_directory)

pecst/resistor/__init__.py

@@ -0,0 +1 @@
+"""Initialize the balancing resistor calculation."""

pecst/resistor/read_resistor_database.py

@@ -0,0 +1,42 @@
+"""Read the resistor database."""
+
+# python libraries
+import pathlib
+import logging
+
+# 3rd party libraries
+import pandas as pd
+import numpy as np
+
+# own libraries
+from pecst import constants as const
+
+logger = logging.getLogger(__name__)
+
+def load_resistors(resistor_series_name: str) -> pd.DataFrame:
+    """
+    Load resistors from the database.
+
+    :param resistor_series_name: name of the resistor series to download
+    :type resistor_series_name: str
+    :return: unified list of resistors
+    :rtype: tuple[pandas.DataFrame]
+    """
+    # resistor data
+    path = pathlib.Path(__file__)
+
+    resistor_series_path = pathlib.PurePath(path.parents[1], const.RESISTORS_DATA_DIRECTORY, resistor_series_name)
+
+    database_path = pathlib.PurePath(resistor_series_path, f"{resistor_series_name}.csv")
+    r_df = pd.read_csv(database_path, sep=',', decimal='.')
+
+    # transfer the datasheet given units to SI units
+    r_df['area'] = r_df["diameter"].astype(float) * r_df["length"].astype(float)
+    r_df['volume'] = (r_df["diameter"].astype(float) / 2) ** 2 * np.pi * r_df["length"].astype(float)
+
+    return r_df
+
+
+if __name__ == "__main__":
+    resistor_df = load_resistors("ac")
+    print(f"{resistor_df}")

pecst/electrolytic/resistors.py pecst/resistor/resistors.pypecst/electrolytic/resistors.py renamed to pecst/resistor/resistors.py

@@ -2,8 +2,10 @@
 
 # 3rd party libraries
 import numpy as np
+import pandas as pd
 
 # own libraries
+from pecst.resistor.read_resistor_database import load_resistors
 
 def generate_resistor_list(e_series_basic_list, potency_list):
     """
@@ -63,6 +65,24 @@ def look_for_closest_smaller_resistance(r_max: float, resistor_list: list) -> fl
         r_closest = resistor_list[index_r_closest]
         return float(r_closest)
 
+
+def look_for_closest_higher_power(power: float, power_list: list) -> float:
+    """
+    Look for the closest higher power in power_list than the given power.
+
+    :param power: power in W
+    :type power: float
+    :param power_list: list of power
+    :type power_list: list
+    :return: closest and higher power in the list
+    """
+    if np.isnan(power):
+        return np.nan
+    else:
+        index_r_closest = np.searchsorted(power_list, [power, ], side='right')[0]
+        p_closest = power_list[index_r_closest]
+        return float(p_closest)
+
 def loss_per_resistor(voltage_per_capacitor: float, resistance: float) -> float:
     """
     Calculate the power loss per resistor.
@@ -79,7 +99,40 @@ def loss_per_resistor(voltage_per_capacitor: float, resistance: float) -> float:
     else:
         return voltage_per_capacitor ** 2 / resistance
 
+def select_resistor_area_volume(power_loss: float, ambient_temperature: float,
+                                r_df: pd.DataFrame) -> pd.Series[float]:
+    """
+    Select the resistor area and volume for a given resistor power dissipation.
+
+    :param power_loss: resistor power loss in W
+    :type power_loss: float
+    :param ambient_temperature: ambient temperature in °C
+    :type ambient_temperature: float
+    :param r_df: resistor database
+    :type r_df: pd.Dataframe
+    :return: area, volume
+    """
+    if power_loss == 0:
+        area = 0.0
+        volume = 0.0
+    else:
+        # interpolate power due to ambient temperature
+        r_df["power_rating_at_ambient_temperature"] = r_df.apply(lambda x: np.interp(
+            ambient_temperature, [-40, 40, 70], [x["power_40_degree"], x["power_40_degree"], x["power_70_degree"]]), axis=1)
+
+        # look for the closest higher temperature
+        higher_rated_power = look_for_closest_higher_power(power_loss, r_df["power_rating_at_ambient_temperature"].to_list())
+
+        # select resistor area and volume
+        area = r_df.loc[r_df["power_rating_at_ambient_temperature"] == higher_rated_power]["area"].values[0]
+        volume = r_df.loc[r_df["power_rating_at_ambient_temperature"] == higher_rated_power]["volume"].values[0]
+    return pd.Series([area, volume])
+
 
 if __name__ == "__main__":
     r_closest = look_for_closest_smaller_resistance(r_max=105, resistor_list=[80, 90, 100, 110, 120])
     print(f"{r_closest=}")
+    resistor_df = load_resistors("ac")
+    [area, volume] = select_resistor_area_volume(2.5, 70, resistor_df)
+    print(f"{area=}")
+    print(f"{volume=}")