Delta MM300 Instruction Manual download pdf (Page 138)

CHAPTER 6: SETPOINTS CONTROL ELEMENTS

MM300 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL 6–51

The starts per hour element defines the number of start attempts allowed in any 60

minute interval. Once the set number of starts has occurred in the last 60 minutes, start

controls are inhibited until the oldest start contributing to the inhibit is more than 60

minutes old.

NOTE

NOTE:

The starts per hour element assumes a motor start is occurring when the relay measures

the transition of no motor current to some value of motor current.

The time between starts element enforces a programmable minimum time duration

between two successive starts attempts. A time delay is initiated with every start and a

restart is not allowed until the specified interval has elapsed. This timer feature may be

useful in enforcing the duty limits of starting resistors or starting autotransformers. It may

also be used to restrict jogging.

NOTE

NOTE:

This time between starts element assumes a motor start is occurring when the relay

measures the transition of no motor current to some value of motor current.

The restart inhibit element may be used to ensure that a certain amount of time passes

between the time a motor is stopped and the restarting of that motor. This timer is useful

for many process applications and motor considerations. If a motor is on a down-hole

pump, the liquid may fall back down the pipe and spin the rotor backwards after the motor

stops. It would be very undesirable to start the motor at this time. This feature is bypassed

by undervoltage immediate restart and by external start.

NOTE

NOTE:

This element assumes a motor stop is occurring when the relay measures the transition of

some value of motor current to no motor current

For each of these features, non-volatile memory is used to make them behave as if they

continue to operate while control power is lost.

Figure 29: Starting duty inhibit setpoints

The following setpoints are available.

[Path: Home > Setpoints > Control > Inhibits]

Start Inhibit Margin

Range: 0 to 10% in steps of 1 or Off

Default: OFF

This setpoint specifies the start inhibit margin. A value of “OFF” disables start inhibits. A

value of 0% causes starts to be inhibited until the thermal capacity used value

calculated by the thermal model drops to 15% or less. Setpoint values in the range of 1

to 10% specify the margin to be included in the calculation of the learned thermal

capacity used at start value, and cause starts to be inhibited until the present thermal

capacity used value drops to the learned thermal capacity used at start value or less.

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