Motor Starting - Generator Voltage Dip

It isn't only a question of the contactors holding in; the 3x to 6x multiple is also necessary to accelerate the motor up to speed, using the mentioned starting methods. This can be improved if using a VFD instead.

Because you need extra oomph from the generator to get the motor away from rest.

If you don't care if the motor actually starts then you can do anything you want. Just don't blame anybody but yourself if any equipment gets damaged from operating things outside of the designed parameters.

Perhaps, I am unclear, but your use of the word "Trip" in describing contactor action is confusing, especially when you state "but the power to the control circuit (contactors, relays) was supplied by solar with batteries and an inverter". This would explain "At motor start up, the generator voltage dipped but the contactors did not trip." If "Trip" is to mean drop out or open.

The starting of a motor, direct on line, requires the generator to be capable of delivering the start or locked rotor current, without collapsing the excitation, engine governor reaction, required engine torque, and flywheel mass.

The contactor is not dropping out because the control circuit voltage is being fed from the solar/battery power source which cannot and is not affected by the dip in generator voltage.

Motor horsepower/watts and design determine how much power is required to start and run a motor.

If the motor supply/generator voltage is dipping during the starting circuit then the generator is not large enough and will fail due to overload.

It is possible to power any motor from a solar system with battery backup.

There are literally millions of sites throughout the world where small to medium size motors are currently being powered by solar systems with battery backup. (Submersible pumps, pump jacks, centrifugal pumps, air conditioning system compressor motors, air compressor motors, etc.)

Limitations are:

1. Physical size and footprint of the solar array and battery bank required to meet the system electrical demand to start and run the selected motor(s).

2. Inherent high cost for purchase, installation, and maintenance of the solar system and batteries.

Hope this helps.

Thank you very much for your and all the other contributions which are highly enlightening and have provided me with the answers I was looking for.

use reduced voltage starter.

Interface the relays/contactors from a separate or independent power supply.

Like this attached photo from transistor to SSR to LV Relays to HV Relays whatever applies to your case.

In Power plants, there is a power supply dedicated to control systems independently. They call it "black start" generator or from some other networks to start the operation.

If efficiency and size is of real concern than why not use a mechanically coupled pump. I mean connect the pump direct to the engine.