System and method for determining defrost power delivered by a defrost heater

申请公布号：: EP1843111(A2)
申请号：: EP20070007062
申请日期：: 2007.04.04
申请公布日期：: 2007.10.10
申请人：: ROBERTSHAW CONTROLS COMPANY
发明人：: ALVORD, ROBERT J.;JENSKI, LEONARD W.;LEASE, BENJAMIN N.
分类号：: F25D21/08
主分类号：: F25D21/08
摘要：: An adaptive defrost control system of the present invention monitors an amount of current flowing through the defrost heater (14) to calculate the instantaneous power and total energy delivered thereby. The circuit utilizes a thermistor (22) to monitor the temperature rise of the electrical trace (30) supplying current to the defrost heater (14) to allow the controller (12) to calculate the amount of current flowing therein. A second thermistor (24) may be used to compensate for a change in ambient temperature that might otherwise be attributed to a change in current flow through the power trace (30). A physical modification (26) to the power trace (30) to enhance the temperature rise characteristic at the point of placement of the thermistor (22) enhances the accuracy of the calculation. A secondary current flow path (28) around the branch of thermistor (22) placement is also provided so as to not reduce the total current carrying capacity of the power trace (30).