I'm trying to build a dyno for electric motors. The dyno consists of two motors: a motor under test (MUT) and a load motor. The two motors are connected together through a shaft. On the shaft there's a torque sensor mounted.
For a load motor, I'm using a Revolt 160 Pro (12kW) with a SEVCON GEN4 controller. The idea is to run the motor from a battery or a power supply (connected to the SEVCON controller). When the load motor is acting as a generator, the three phase terminals of the load motor are gonna be switched to a circuit with a dump load to dissipate all the generated power.
My question is: let's say that I have an 8Nm clockwise input on the MUT and a 4Nm clockwise input on the load motor (since I want to load the MUT with 4Nm). The net result on the shaft it's going to be 4 Nm (clockwise referred to the MUT). Therefore, the load motor is going to act as a generator. When it's acting as a generator, the SEVCON controller and power supply are no longer part of circuit, the load motor is just connected to a circuit with a dump load. How can I control the load motor (now acting as a generator) so now it loads the MUT with exactly 4Nm? Do I need to have a variable and controllable dump load to achieve this application?
EDIT: This is a rough schematic of the circuit of the dynamometer on the load side. There's two circuits, one used for the motor when it acts as a generator and another one used when the motor acts as a motor (and therefore it's controlled by a SEVCON controller). My question was how to control the motor when it acts as a generator, i.e. how to control the generator's load on the shaft.