ABB SPAM150C Motor Protection Relay

Brief Introduction

The SPAM150C Motor Protection Relay is a general purpose combination relay designed primarily for the protection of AC motors for a variety of applications.

It combines a large number of protection functions in one unit. The relay provides a complete set of protection against motor damage caused by various electrical faults.

The relay is also suitable for other equipment requiring thermal overload protection, such as cable or power transformer feeders.

Summary of Protection Functions

The relay thermal overload unit protects the motor against short- and long-term overloads. The maximum permissible continuous load depends on the setting value 1.

Normally this setting value is taken as the rated full load current (FLC) of the motor at an ambient temperature of 40°C. The motor can be overloaded for a short period of time if the motor is not loaded.

When the motor current increases to 1.05I under the above conditions, the thermal overload unit starts after a certain delay.

If the ambient temperature of the motor is below 40°C for a long period of time, the setting value I. can be set to .05...1.10 times the full load current (FLC) of the motor. 1.10 times.

The short-time overload phenomenon mainly occurs during the starting process of the motor. The motor is normally allowed to start twice under cold conditions and once under hot conditions.

One start is permitted under hot conditions, therefore, depending on the starting time of the motor, an integrating value t determining the characteristics of the thermal overload unit can be derived.

This value can be easily determined from the time/current graph in the hot state. t curve is selected from the starting current versus the corresponding starting time (with an appropriate margin).

The t-curve is selected from the starting current versus the corresponding starting time (with an appropriate margin). Using the same value of t, the total permissible starting time of the motor under cold conditions can be found from the cold curve.

As a rule of thumb, for two cold starts or one hot start, the t-value is set to 1.6...2.0 times the starting time of the motor. ...2.0 times.

The thermal overload pre-warning signal can warn the operator to reduce the load of the motor when thermal overload occurs, thus avoiding unnecessary thermal overload tripping.

This can avoid unnecessary thermal overload tripping. The setting value of the pre-warning signal can be individually set to a certain percentage of the thermal overload tripping value.

Therefore, by choosing the appropriate pre-warning signal setting value, the motor can be operated close to the thermal capacity limit value while avoiding tripping due to prolonged overload.

Every time the motor is started, the start-up monitoring unit monitors the thermal consumption of the motor, usually in accordance with the It formula.

Alternatively, a fixed time limit overcurrent can be used. The latter is mainly used for equipment with non-motor loads.

In either case, a speed switch signal such as that mounted on the motor shaft to distinguish between motor blocking and normal starting can be programmed into the relay to control the output trip command.

to control the output trip command. A high value overcurrent protection unit (current cut-off) for protection against short-circuits between motor windings and short-circuits between phases of feeder cables.

The current setting value can be set so that it is automatically doubled during start-up. Therefore, the setting value can be set lower than the motor starting current.

Normally it can be set as low as 0.75 times the motor starting current. In addition, an appropriate action time should be set to match.

In this way, when the motor is blocked during operation, the current interruption protection unit can ensure reliable operation.

When the motor is controlled by a contactor, the high value overcurrent protection unit should be blocked and the fuse should be used to protect against short circuits.

The non-directional earth fault unit detects earth faults in the motor and feeder circuits. In the neutral point directly grounded or through the low impedance grounding system, the CT can be connected to a residual ground fault.