Starters and motors

[ElectroChem]

Any motor in good condition will survive if the protection is set right and adequate ... the problem is this is not the case with half the crap out there .... ...if the motor hums and doesn't move you are turning the windings into a heater coil tht will self destruct if not stopped ( In the case of a standard squirrel cage)

If I had a penny for every time we've attended a burnt out motor to find the TOL either cranked up to max or absent...

I still couldn't buy anything because I'm in Australia and we haven't had pennies since 1950 something, dammit.

 

[jamie-spark]

Deleted oops

 

[Jonspark]

looking at the motor name plate thats a hazardous area motor suitable for dust environments, and as such should you be running it without the lid on?

 

[Lucien Nunes]

why nit not just break live with e stops , forget control boards ...��

The injection brake uses phase-angle controlled rectification to pass DC through the stator winding, creating a stationary magnetic flux instead of a rotating one. The current induced in the rotor cage is also stationary in space and like an eddy-current brake this produces torque in the opposite direction to rotation, rapidly slowing the machine as though there was a physical brake on the shaft. Braking is mandatory on certain kinds of machinery where there is increased risk if the machine is allowed to coast down to a stop, so it was totally relevant to mention that this is on a bandsaw.

As for your first Q - 230V everywhere but no 400, suggests one phase only is connected. Note that the brake is not a full 3-phase bridge and will produce some funny-looking readings at the motor terminal.

Oops double post... dunno how that happens.

 

[R G]

I was told of a similar type of motors on later underground trains , where they have a selector for rheostat 1, 2 and hold , the motors are 630v DC , and they become generators on braking and this generated voltage is sent to the other motor in reverse windings , and thats the noise you hear when approaching before application of the main braking system ...

 

[Lucien Nunes]

DC motors are inherently capable of regeneration, and have been used with dynamic braking for a century or more. PM motors are the simplest - just short the terminals - car windscreen wipers usually park like this. Induction motors are not so easy because reconfiguring the supply to give reverse torque stands the risk of the motor starting up in reverse. So it takes an extra piece of kit, the rectifier (and transformer, if the rectifier is not phase controlled) to brake an induction motor. Of course with 4-quadrant PWM drive anything is possible. OP: look up 4-quadrant motor control.

 

[netblindpaul]

But as said why only getting 230v motor connections,

why nit not just break live with e stops , forget control boards ...

There is a LOT more to it than that, the three items are, DOL starter, motor TM O/L, DC injection braking module.
The requirement is enshrined in the MD, and is stipulated in the various A, B & C type standards.
A bandsaw is an Annexe iv machine.
E-stops are NOT load switching devices, and must never be used as such.
The assembly is an SRPCS, thus it must meet certain standards, based on the relevant as I have said, A, B & C type standards for the machine and control system under consideration.
Looking at this I would also hazard that the machine is CE marked.