Yes, if motor rated voltage match.

Yes, but in this case you will lose the capability to control motor speed, which is generally performed through the converter regulating the armature current.

If uncontrolled operation is OK for you then you can go with direct connection to the bus.

If you still want to achieve some level of controllability, allow me to suggest to have a look at my paper " Analysis of a fault-tolerant hybrid-excitation DC motor " here on RG: we proposed to have the armature directly connected to the DC bus, while auxiliary excitation windings (wound around the PMs of the DC motor) are supplied by dedicated converter (of small power) and provide the possibility to control the field and thus the speed of the motor.

Article Analysis of a fault-tolerant hybrid-excitation DC motor

Yes, of course.

But you must consider if motor regulation is necessary.

depends upon rating of both DC motor and DC bus

Pls explain more on the rating, which must be higher?

Dear Adebayo,

One of the important requirement on the DC motor that it must be soft started other wise a very large surge current can pass in the armature winding and may harm it. So, one has to provide for the soft start. The other issue is that at least the voltage of the bus must be equal or smaller than the rated voltage of the motor. Also, any variations in the bus voltage will cause variation in the speed of the motor. I do not know what do you use the motor for. I think the use of the DC/DC converter is necessary for safety and controlled operation of the DC motor.

Best wishes