Selsyn

Instrumentation selsyns have no use for starting resistors. (Figure above) They are not intended to be self rotating. Since the rotors are not shorted out nor resistor loaded, no starting torque is developed. However, manual rotation of one shaft will produce an unbalance in the rotor currents until the parallel unit's shaft follows. Note that a common source of three phase power is applied to both stators. Though we show three phase rotors above, a single phase powered rotor is sufficient.

Pony motor

Purpose: To minimize starting current when starting a large motor in an unloaded condition

Pony motor

Sequence of Operation:

1)Start signal to the Pony Starter Logic causes the EZ6 to accelerate the Pony Motor in a current limit condition (typically 300% full load), which in turn accelerates the main motor.

2)When the “up to speed” circuit in the EZ6 senses that acceleration I s complete, it causes the Pony Starter Logic to disable the EZ6 and then enable the main motor starter. Since the main motor is already at full speed, starting current is nearly non-existent (there will be a short surge of current to magnetize the windings.) 3)

3)The loading mechanism (clutch, feeder, etc.) is then activated by an auxiliary contact from the main starter to apply the load. A stop signal to the Pony Starter Logic disables the main starter and resets the Pony

Starter Logic for another sequenced start.

4)A stop signal to the Pony Starter Logic disables the main starter and resets the Pony Starter Logic for another sequenced start.

Pony motor

Protection:

Since the acceleration time for the Pony Motor precludes use of standard overload protection, stall protection is provided by a stall time circuit which will disable the Pony Starter Logic and provide an alarm contact if the Pony Motor fails to reach full speed in the preset time. A stall trip requires manual reset at the Pony Starter.

It was the best cadets from

Kherson

Sergey Kravchenko

State

And

AndreyMaritimeProkopenko

Academy