The test rig used for efficiency and loss mapping is shown in Fig.1. The test rig consists of the following main elements:
- Motor under Test (MUT) is an Internal Permanent Magnets (IPM) motor
- The motor controller is a dSpace board with a dedicated analog/digital interface
- The Driving Motor (DM) is a speed-controlled Permanent Magnet (PM) motor fed by a bi-directional converter whose speed reference is provided by the dSpace board using an analog dSpace DAC (digital-to-analog converter) output. Another solution is to use a CAN or RS422 interface, depending also of the communication capability of the converter that supplies the DM
- The torque is measured with the high accuracy HBM T40 torque sensor(Fig. 2) that provides the shaft torque and also the shaft position with a resolution of 1024 pulses/rev (encoder type outputs). The torque sensor is mounted as a mechanical coupler between the MUT shaft and the DM shaft. The data are transmitted to the measurement system by means of a rotating transformer.
- The phase currents are measured with high accuracy, external LEM sensors (Fig. 3) that are fed by a current sensor box that manages the current sensors and generates the outputs that are acquired by the HBM data recorder with the high-speed acquisition channels with a sampling rate of 2Msamples/s. The voltage drops on the LEM shunts are sent to the Gen3i using BNC cables.
- The MUT line-to-line voltages are directly measured by the Gen3i recorder using the high-voltage/high-speed acquisition channels with a sampling rate of 2Msamples/s. In this way, the acquired voltages are the real PWM pulses that are applied to the machine.
- Besides the rotor position provided by the T40 torque sensor, the Gen3i measures also the rotor position using an incremental encoder that is also employed by the motor controller (as shown in Fig. 1). An external splitter card receives the encoder pulses from the encoder and sends them to the motor controller and to the Gen3i with galvanic insulation.
- The motor temperature is measured by means of three thermocouples. The thermocouples are read by programmable isolation amplifiers (Fig. 4) whose outputs are provided to a low speed acquisition card of Gen3i.
The MUT and DM are shown in Fig. 5, while Fig. 6 contains a general view of the entire test rig, including the HBM Gen3i data recorder.