Martin Ganchev

A Detailed Heat and Fluid Flow Analysis of an Internal Permanent Magnet Synchronous Machine by Means of Computational Fluid Dynamics

This paper presents a comprehensive computational fluid dynamics (CFD) model of a radial flux permanent magnet synchronous machine with interior magnets. In the CFD model, the water jacket cooling and a simplified model of the topology of the distributed stator winding are considered. The heat sources of the CFD model are determined from a finite-element analysis of the machine. The numerically determined temperature distributions of the machine are compared with measurement results from sensors located both in the stator and rotor. The particular focus of this paper is the analysis of the temperatures and the heat flow in the air gap and from the stator winding heads and the rotor to the inner air. Different operating conditions and two particular rotor designs with different inner air flow configurations are investigated. The potential of improving the thermal utilization of a rotor design with fan blades attached to the mounting plates of the rotor is shown.

Sensorless rotor temperature estimation of permanent magnet synchronous motor

The work proposes a method for estimation of the magnet temperature in permanent-magnet synchronous machines by exploiting the d-axis saturation effects in the steel stator core produced by the d-current and rotor flux excitation. The method implies an intermittent injection of a voltage pulse in the d-axis of the motor. The resulting d-current response is a function of both the initial value of the d-current itself and the magnetization level of the magnets. Thus, a temperature dependent variation in the magnetization level of the permanent magnets is reflected in a variation of the d-current slope upon the voltage pulse. Experimental validation of the method is demonstrated with surface permanent-magnet motor.

Compensation of Speed Dependence in Sensorless Rotor Temperature Estimation for Permanent-Magnet Synchronous Motor

This paper proposes an improved method for estimating the magnet temperature in permanent-magnet synchronous machines without using any temperature sensors. Originally, the method implies an intermittent injection of a voltage pulse in the positive d-axis of the motor while keeping the load current zero. Thus, the resulting d-current response depends on both the initial value of the d-current itself and the actual magnetization level of the permanent magnets. Since the magnetization of the magnets depends on the temperature, different d-current slopes are associated with given temperature levels of the magnets. At higher speeds, the current response is additionally affected by induced voltages of various sources which lead to erroneous estimation of the magnet temperature. By applying a voltage pulse in the positive and negative d-axis of the motor, symmetry of the induced voltages can be achieved in a manner that the difference of the current responses from the positive and negative pulses is no longer affected by the induced voltages.

Rotor temperature distribution measuring system

The work proposes instrumentation for measuring local temperatures on the surface and in the interior of a rotor. The applied design incorporates up to 12 simultaneous local temperature measurements on arbitrary locations in the rotor. Thus, a realistic 3D thermal distribution picture of the rotor can be obtained. The system characterizes with accuracy of α1.5 °C, noise immunity under inverter operation, continuous measuring durations of up to 30h and mechanical rigidity for up to 6000 rpm rotor speed. The mechanical assembly is appropriate for laboratory setups since adaptation on the motor are required. Experimental results, conducted on an induction motor and permanent-magnet synchronous motor, are presented to demonstrate system feasibility.

Rotor temperature monitoring system

The paper discusses some of the basic developments in the field of direct measurements of the rotor temperature of an electrical motor. In the same context, the design of a state-of-the-art rotor temperature monitoring system for contact measurements is proposed. The data transmission between the rotating and stationary part is realized via infrared light. The used temperature sensors are thermocouples of type K. The design applies the simultaneous processing of up to 12 sensors. Power is supplied by a battery placed in the rotating instrumentation. As a whole, the system is characterized by high noise immunity, low power consumption for long experimental setups and mechanical rigidity for up to 6000 rpm. The mechanical assembly is appropriate for laboratory setup since adaptation on the motor are required. Finally, experimental results are presented to show system feasibility.

Identification of sensorless rotor temperature estimation technique for Permanent Magnet Synchronous Motor

Reversible demagnetization effects due to temperature increase is a common problem in rare-earth magnets widely used in Permanent Magnets Synchronous Machines (PMSM). Variation of the magnetization level of the magnets leads to different saturation levels in the steel stator core of the machine. The paper proposes a simple method to detect magnetization variation by an intermittent injection of a voltage pulse in the d-axis of the motor, while the q-current is kept zero. The slope of the resulted d-current response reflects a given saturation level which is distinctive for a given magnet temperature. Since this is a strongly non-linear relationship, a look-up-table (LUT) for the motor is required. The paper proposes a procedure where the identification of the LUT without measuring directly the rotor temperature can be achieved at standstill.

Heat and fluid flow analysis of an internal permanent magnet synchronous machine by means of computational fluid dynamics

This paper presents a comprehensive computational fluid (CFD) model of a radial flux permanent magnet synchronous machine with interior magnets. In the CFD model the water jacket cooling and a simplified model of the topology of the distributed stator winding are considered. The heat sources of the CFD model are determined from a finite element analysis of the machine. The numerically determined temperature distributions of the machine are compared with measurement results from sensors located both in the stator and rotor. The particular focus of this paper is the analysis of the temperatures and the heat flow in the air gap and from the stator winding head and the rotor to the inner air.

Hardware and software implementation of sensorless rotor temperature estimation technique for Permanent Magnet Synchronous Motor

The paper focuses on the hardware and software implementation of a novel sensorless rotor temperature estimation technique for Permanent Magnet Synchronous Machines (PMSMs). The method requires an intermittent injection of a voltage pulse in the d-axis of the motor while the q-current is kept zero. The slope of the resulted d-current response reflects a given saturation level of the machine stator steel core which is distinctive for a given magnet temperature. Since this is a strongly non-linear relationship, a look-up-table (LUT) for the motor is required. In order to capture correctly the current derivative, a synchronous oversampling of the d-current along the voltage pulse duration is required. The paper demonstrates a suitable hardware setup and software integration of the method into a common field oriented space vector control.

Sensorless rotor temperature estimation of permanent magnet synchronous motor under load conditions

The work proposes a method for estimating the magnet temperature in permanent magnet synchronous machines (PMSMs) under load conditions. The method implies an intermittent injection of a voltage pulse in the positive and negative d-axis of the motor. Thus, the difference of the resulting d-current responses depends on the machine operating point which is defined by the d-current, the q-current and the actual magnetization level of the permanent magnets. Since the magnetization of the magnets depends on the temperature, different d-current slopes reflect different temperature levels of the magnets. By applying a voltage pulse in the positive and negative d-axis of the motor, symmetry of the induced voltages can be achieved in a manner that the difference of the current responses from the positive and negative pulse is to a great extent speed independent.

Dual DSP concept for a motor controller platform used in Hardware-In-The-Loop simulation environments

The work proposes a design of a controller platform for advanced digital motor control used in hardware-in-the-loop (HIL) simulation environments. The platform is a synergistic combination of two parallel processing computing cores, where one is powerful floating point digital signal processor (DSP) used for the main computing routines and the other one is a fixed point DSP with on-chip peripherals for motor control applications. The applied software scheduling implies real-time multitasking operating system with task switching times less than 300 ns reducing the overhead to minimum possible for the given floating point DSP. The sample period of the main control cycle is arbitrary adjustable from 1 ms to up to 10 mus making the system applicable in a wide range of experimental setups. The operating system was designed to handle asynchronous read and/or write events from and to real-time workstations for HIL simulations. An application graphical user interface (GUI) based on high speed IEEE1394 data exchange provides the user with the ability to monitor and modify virtually every software variable defined as global in the control software.